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Integrated Agri-Aquaculture 

Demonstration Facility 

Using irrigation storages for intensive native fish culture 

RIRDC Publication No. 09/060 

RIRDCInnovation for rural Australia




By Dr Adrian Collins 

Mr Andrew Walls 

Mr Benjamin Russell 

April 2009 

RIRDC Publication No 09/060 

RIRDC Project No DAQ-290A

© 2009 Rural Industries Research and Development Corporation. 

All rights reserved. 

ISBN 1 74151 862 8 

ISSN 1440-6845 

Integrated Agri-Aquaculture Demonstration Facility - Using irrigation storages for intensive native fish culture 

Publication No. 09/060 

Project No. DAQ-290A 

The information contained in this publication is intended for general use to assist public knowledge and discussion 

and to help improve the development of sustainable regions. You must not rely on any information contained in 

this publication without taking specialist advice relevant to your particular circumstances. 

While reasonable care has been taken in preparing this publication to ensure that information is true and correct, 

the Commonwealth of Australia gives no assurance as to the accuracy of any information in this publication. 

The Commonwealth of Australia, the Rural Industries Research and Development Corporation (RIRDC), the 

authors or contributors expressly disclaim, to the maximum extent permitted by law, all responsibility and liability to 

any person, arising directly or indirectly from any act or omission, or for any consequences of any such act or 

omission, made in reliance on the contents of this publication, whether or not caused by any negligence on the 

part of the Commonwealth of Australia, RIRDC, the authors or contributors. 

The Commonwealth of Australia does not necessarily endorse the views in this publication. 

This publication is copyright. Apart from any use as permitted under the Copyright Act 1968, all other rights are 

reserved. However, wide dissemination is encouraged. Requests and inquiries concerning reproduction and rights 

should be addressed to the RIRDC Publications Manager on phone 02 6271 4165. 

Researcher Contact Details 

Dan Willett 

Project Leader Integrated Aquaculture 

c/- Bribie Island Aquaculture Research Centre 

PO Box 2066 

Bribie Island QLD 4507 

Phone: 07 3400 2000 

Fax: 07 3408 3535 

Email: bribie@dpi.qld.gov.au 

Website: www.dpi.qld.gov.au 

In submitting this report, the researcher has agreed to RIRDC publishing this material in its edited form. 

RIRDC Contact Details 

Rural Industries Research and Development Corporation 

Level 2, 15 National Circuit 

BARTON ACT 2600 

PO Box 4776 

KINGSTON ACT 2604 

Phone: 02 6271 4100 

Fax: 02 6271 4199 

Email: rirdc@rirdc.gov.au. 

Web: http://www.rirdc.gov.au 

Electronically published by RIRDC in April 2009 

Print-on-demand by Union Offset Printing, Canberra at www.rirdc.gov.au 

or phone 1300 634 313 

ii

Foreword 

The integration of aquaculture with traditional agriculture can provide a practical means for farmers to 

maximise their use of valuable water resources and infrastructure. This multiple use of water is 

practiced in many of the driest regions of the world where water is used, but not directly consumed, by 

the aquaculture operation and can then be used to irrigate the farm’s terrestrial crops. 

The Darling Downs region in southern Queensland is a hub for agriculture and contains large numbers 

of constructed water storages or ‘ring tanks’ to provide water for irrigation. The major irrigated crop in 

this region is cotton. The cotton industry’s access to this water infrastructure, and its location to 

markets and within the natural distribution of suitable native fish for culture, makes it a particularly 

suitable candidate to demonstrate the feasibility of integrating aquaculture into established farming 

operations. This project was an on-farm demonstration to highlight the needs, operational challenges 

and potential of integrated farming systems across rural Australia. 

The project screened a number of native fish species for their suitability to culture conditions in the 

farm’s primary water storage, within production systems that included floating cages and raceways. 

The floating raceways developed in this project were the first of their kind in Australia and proved to 

be an ideal fish culture system for permanent and non-specific water bodies (that is, water bodies not 

specifically designed as harvestable aquaculture ponds). This was due to their cost effectiveness and 

the improved management they offer in terms of stock inventory, feeding, growth and disease 

monitoring, predator control and harvesting. 

This study also highlighted the problems for integrating aquaculture with cotton production. In 

particular, integration requires changes to established water management practices to ensure adequate 

water quality is maintained for the aquaculture operation. Co-ordinating pumping events, maintaining 

appropriate volume in storages and managing overland flows from floods and tailwaters are vital for 

maintaining sound conditions for fish culture. Especially important is preventing pollutants such as 

pesticides from entering waters used for aquaculture due to the risk that pesticide residues can 

accumulate in fish tissues to unacceptable levels. 

Technically, aquaculture is a specialised discipline, and integrated operations with shared farm labour 

will require additional investment in aquaculture training to recognise and manage the needs of fish 

culture. However, the irrigation industry is well placed to make such investment because of its existing 

water infrastructure and because of its commitment to environmental management and sustainability. 

Successful integration would provide significant socio-economic benefits for growers as well as a 

number of other rural industries and their communities. 

The report, an addition to RIRDC’s diverse range of over 1800 research publications, forms part of our 

Environment and Farm Management R&D program which aims to support innovation in agriculture 

and the use of frontier technology to meet market demands for accredited sustainable production. 

Most of RIRDC’s publications are available for viewing, downloading or purchasing online at 

www.rirdc.gov.au. Purchases can also be made by phoning 1300 634 313. 

Peter O’Brien 

Managing Director 

Rural Industries Research and Development Corporation 

iii

Acknowledgments 

The authors would like to thank Mr Paul McVeigh and family for access to their farm, use of their 

facilities for demonstration and research activities, for the information provided concerning their 

whole of farm operations and general support for the project. Thanks also to Mark Taylor for his 

contribution to the conduct of onfarm trials. 

The authors would like to acknowledge the contributions and support of other DPI&F staff past and 

present, namely Peter Peterson, John Robertson, Paul Grieve, James Butler, Kelvin Spann, John 

Standley and Trent Lindsay. 

Abbreviations 

Abbreviation 

ABS 

ACG 

AGAL 

AGBOM 

AlSO 4 

APHA 

APVMA 

AQIS 

BCF 

BMP 

BOD 

CBWC 

cm 

CRDC 

DAFF 

DDD 

DDE 

DDT 

DO 

DPI&F 

EAR 

EPA 

ERL 

EXTOXNET 

FCR 

FL 

FSANZ 

FSDkg/m 3 

FW 

g 

G%/day 

GL 

ha 

HDPE 

hrs 

IAAS 

IPCS 

IPM 

IRR 

ISDkg/m 3 

IW 

Meaning 

Australian Bureau of Statistics 

The Australian Cotton Grower 

Australian Government Analytical Laboratories 

Australian Government Bureau of Meteorology 

Aluminium sulphate 

American Public Health Association 

Australian Pesticides and Veterinary Medicines Authority 

Australian Quarantine and Inspection Service 

Bio-concentration factors 

Best Management Practices 

Biological oxygen demand 

Condamine-Balonne Water Committee 

Centimetre 

Cotton Research and Development Corporation 

Department of Agriculture Fisheries & Forestry 

Dichlorodiphenyldichloroethane 

Dichlanodiphenyldichloroethylene 

Dichlorodiphenyltrichloroethane 

Dissolved oxygen 

Department of Primary Industries and Fisheries 

Equivalent Annual Return 

Environmental Protection Agency 

Extraneous residue limit 

Extension Toxicology Network 

food conversion rate 

Floor 

Food Standards Australia New Zealand 

Final stocking density 

Final weight 

Grams 

Daily percentage growth 

Giga litre 

Hectares 

High density polyethylene 

Hours 

Integrated Agri-Aquaculture Systems 

International Programme on Chemical Safety 

Integrated Pest Management 

Internal Rate of Return 

Initial stocking density 

Initial weight 

iv

Abbreviation Meaning 

kg 

Kilograms 

km 

Kilometres 

L 

Litre 

LC 

Lethal concentration 

LOQ 

Limit of Quantitation 

m 

Metre 

m 3 

Cubic metres 

mg 

Milligram 

mg/L 

Milligrams per litre 

min 

Minutes 

ML 

Mega litre 

ml 

Millilitres 

mm 

Millimetres 

MPR 

Modular plastic raceways 

MRL 

Maximum residue limit 

N 

Nitrogen 

N/m 3 

Number per cubic meter 

NPTN 

National Pesticide Telecommunications Network 

NPV 

Net present value 

NRA 

National Registration Authority 

NRS 

National Residue Survey 

OC 

Organochlorine 

ºC Degrees Celsius 

OP 

Organophosphate 

P 

Phosphorus 

P/L 

Proprietary Limited 

PAC 

Powdered activated carbon 

PAN 

Pesticide Action Network 

PIRSA 

Primary Industries and Resources South Australia 

PMEP 

Pesticide Management Education Program 

ppt 

Parts per thousand 

PV 

Present value 

RIRDC Rural Industries Research and Development Corporation 

SF 

Surface water 

SP 

Synthetic pyrethroids 

sp. 

Species 

t 

Tonne 

TAMCO Total Aquaculture Management Company 

TKN 

Total Kjeldahl Nitrogen 

TKP 

Total Kjeldahl Phosphorous 

USA 

United States of America 

USEPA United States Environmental Protection Agency 

V 

Volt 

VDPI 

Victorian Department of Primary Industries 

WHO 

World Health Organization 

βHCH 

Beta hexachlorocyclohexane 

μg/l 

Micrograms per litre 

v

Contents 

Foreword ............................................................................................................................................... iii 

Acknowledgments................................................................................................................................. iv 

Abbreviations........................................................................................................................................ iv 

List of Figures .................................................................................................................................... ix 

Executive Summary ............................................................................................................................. ix 

What the report is about ...................................................................................................................... x 

Who the report is targeted at ............................................................................................................... x 

Background ......................................................................................................................................... x 

Aims .................................................................................................................................................... x 

Methods used...................................................................................................................................... xi 

Results ................................................................................................................................................ xi 

Implications and Recommendations.................................................................................................. xii 

1. Introduction ....................................................................................................................................... 1 

2. Demonstration Farm......................................................................................................................... 4 

2.1 Background ................................................................................................................................... 4 

2.2 Aquaculture Systems..................................................................................................................... 5 

2.3 Fish Species................................................................................................................................... 7 

3. Water Use and Quality...................................................................................................................... 8 

3.1 Background ................................................................................................................................... 8 

3.2 Materials and Methods .................................................................................................................. 8 

3.3 Results ........................................................................................................................................... 9 

3.4 Discussion ................................................................................................................................... 15 

4. Production Systems and Growth ................................................................................................... 18 

4.1 Background ................................................................................................................................. 18 

4.2 Materials and Methods ................................................................................................................ 18 

4.3 Results ......................................................................................................................................... 27 

4.4 Discussion ................................................................................................................................... 37 

5. Pesticide Monitoring and Residues................................................................................................ 42 

5.1 Background ................................................................................................................................. 42 

5.2 Materials and Methods ................................................................................................................ 43 

5.3 Pesticide Bio-concentration and Depuration............................................................................... 45 

5.4 Results ......................................................................................................................................... 47 

5.5 Discussion ................................................................................................................................... 50 

6. Integrated Production Decision Tool............................................................................................. 55 

6.1 Description .................................................................................................................................. 55 

7. General Discussion .......................................................................................................................... 56 

Appendix 1 ........................................................................................................................................... 58 

References ............................................................................................................................................ 72 

vi

Tables 

Table 3.3.1 

Table 3.3.2 

Table 3.3.3 

Table 3.3.4 

Table 3.3.5 

Table 4.3.1 

Table 4.3.2 

Table 4.3.3 

Table 4.3.4 

Table 4.3.5 

Table 4.3.6 

Table 4.3.7 

Table 4.3.8 

Table 4.3.9 

Table 4.3.10 

Source, timing and duration of water harvesting activities at Loch Eaton from October 

2000 to February 2004 ............................................................................................................... 9 

Average monthly morning surface (SF) and floor (FL) dissolved oxygen levels (mg/L) in the 

aquaculture ring tank from November 2000 to March 2004 (mean ± standard deviation) ...... 11 

Average monthly afternoon ring tank surface (SF) and floor (FL) dissolved oxygen levels 

(mg/L) from November 2000 to March 2004 (mean ± standard deviation)............................. 12 

Average monthly morning ring tank surface (SF) and floor (FL) water temperatures from 

November 2000 to March 2004 (mean ± standard deviation).................................................. 12 

Average monthly afternoon ring tank surface (SF) and floor (FL) water temperatures from 

November 2000 to March 2004 (mean ± standard deviation).................................................. 13 

Number and volume of net cages and floating raceways in operation at Loch Eaton from 

September 2000 through to March 2004.................................................................................. 28 

List of known stock escape events at Loch Eaton, estimated numbers of fish lost and the 

observed cause of each escape event........................................................................................ 28 

The length of culture period (Days), number per cubic meter (N/m 3 ), initial weight (IW), final 

weight (FW), initial stocking density (ISDkg/m 3 ), final stocking density (FSDkg/m 3 ) and daily 

percentage growth (G%/day) for silver perch (Bidyanus bidyanus) held in 8 and 100m 3 net 

cages from the 07/12/00 up to the 31/01/01 ............................................................................. 30 

The length of culture period (Days), number per cubic meter (N/m 3 , initial weight (IW), final 

weight (FW), initial stocking density (ISDkg/m 3 ), final stocking density (FSDkg/m 3 ), percent 

stock retention (%SR) and daily percentage growth (G%/day) for silver perch (Bidyanus 

bidyanus) held in 8 and 100m 3 net cages from the 30/01/01 up to 26/04/01 in 8 and 100m 3 net 

cages......................................................................................................................................... 30 

.The length of culture period (Days), number per cubic meter (N/m 3 ), initial weight (IW), final 



bidyanus) held in 8 and 100m 3 net cages from the 02/03/01 up to 27/09/01 in 8 and 100m 3 net 

cages......................................................................................................................................... 30 


weight (FW), initial stocking density (ISDkg/m 3 ), final stocking density (FSDkg/m 3 ), stock 

retention (%SR) and daily percentage growth (G%/day) for silver perch (Bidyanus bidyanus) 

from the 02/03/01 up to 27/09/01 in 7 and 14m 3 raceways...................................................... 31 



stock retention (%SR) daily percentage growth (G%/day) and food conversion ratio (FCR)for 

silver perch (Bidyanus bidyanus) from the 02/03/01 up to 27/09/01 in 7 and 14m 3 raceways 33 



stock retention (%SR), daily percentage growth (G%/day) and food conversion ratio (FCR) for 

silver perch (Bidyanus bidyanus) from the 02/03/01 up to 27/09/01 in 7 and 14m 3 raceways. 33 




silver perch (Bidyanus bidyanus) from the 05/02/02 up to 07/05/02 in 7 and 14m 3 raceways as 

well as a single 12m 3 raceway.................................................................................................. 33 


weight (FW), initial stocking density (ISDkg/m 3 ), final stocking density (FSDkg/m3), percent 


silver perch (Bidyanus bidyanus) from the 19/07/02 up to 21/10/02 in 7 and 14m 3 raceways. 34 

vii

Table 4.3.11 

Table 4.3.12 

Table 4.3.13 

Figure 4.4.1 

Table 5.1.1 




silver perch (Bidyanus bidyanus) from the 06/11/02 up to 18/02/03 in 12 and 17.5m 3 raceways 

as well as a single 14m 3 raceway.............................................................................................. 36 




silver perch (Bidyanus bidyanus) from the 20/02/02 up to 25/03/03 in 12 and 17.5m 3 

raceways. .................................................................................................................................. 37 




silver perch (Bidyanus bidyanus) from the 08/04/03 up to 08/04/04 in 12, 17.5 and 23m 3 

raceways. 37 

Existing (E) and recommended (R) locations of aquaculture facilities and pumping 

infrastructure at Loch Eaton. Relocation of the floating raceway facility from the primary ring 

tank to the adjacent storage would serve to buffer the aquaculture facility from acute falls in 

dissolved oxygen as the result of harvesting large volumes of oxygen deficient, highly turbid 

flood waters.............................................................................................................................. 40 

Extraneous Residue Limits (ERL) for agricultural chemicals in whole fish (minus gut) 

according to Food Standards Australia New Zealand, Australia New Zealand Food Standards 

Code (FSANZ, 2006) ............................................................................................................... 42 

Table 5.2.1 List of agri-chemicals used at Loch Eaton from February 2001 to May 2003......................... 44 

Table 5.2.2 

Table 5.2.3 

List of organochlorine, organophosphate and pyrethroid compounds included in analytical 

testing of riverine and ring tank water samples........................................................................ 44 

List of organochlorine, organophosphate and synthetic pyrethroid compounds included in 

analytical testing of fish samples.............................................................................................. 45 

Table 5.4.1 Ranges of agents detected in Ring tank water.......................................................................... 47 

Table 5.4.2 Ranges of agents detected in River water................................................................................. 47 

viii

Figures 

Figure 2.1.1 

Area map of McVeigh Brothers properties Loch Eaton and Timberline located near Dalby, 

Queensland...................................................................................................................................... 4 

Figure 2.1.2 Layout of the McVeigh Brothers properties showing farm infrastructure...................................... 5 

Figure 2.2.3 Net cages used for silver perch and Murray cod production in the ring tank at Loch Eaton .......... 6 

Figure 2.2.4 Floating raceway system developed for intensive fish production deployed in the ring tank at 

Loch Eaton ........................................................................................................................................ 6 

Figure 3.3.1 Daily turbidity readings for the aquaculture ring tank from January 2001 to March 2004 reported 

weekly. The red dashed line indicates a major riverine pumping event ....................................................... 14 

Figure 3.3.2 Total Kjeldahl Nitrogen (TKN) and Total Kjeldahl Phosphorous (TKP) in the Condamine River 

and Loch Eaton ring tank waters. ................................................................................................... 15 

Figure 4.2.1 Net cages 8m 3 used for silver perch and Murray cod fingerlings and juveniles.............................. 19 

Figure 4.2.2 Net cages 100m 3 used for silver perch grow out ............................................................................. 19 

Figure 4.2.3 The first 7m 3 floating plastic raceway being stocked with silver perch fingerlings at Loch Eaton. 20 

Figure 4.2.4 The first 14m 3 floating plastic raceways were constructed from HPDE sheets welded to rectangular 

pontoons that provided buoyancy.................................................................................................... 20 

Figure 4.2.5 The first 12m 3 TAMCO roto-moulded raceways in use at Loch Eaton .......................................... 21 

Figure 4.2.6 A bank of uplifts (100mm) drives the water exchange through each of the raceway units............. 21 

Figure 4.2.7 Uplift, baffle board and end screen of raceways ............................................................................. 22 

Figure 4.2.8 Water flow characteristics of raceways without an eddy board ...................................................... 23 

Figure 4.2.9 Water flow characteristics of raceways with an eddy board placed 120cm from the water entrance 

and extended 20cm from the surface............................................................................................... 23 

Figure 4.2.10 Purging tanks (10m 3 ) supplied with degassed bore water were used to clear silver perch of ‘off 

flavour’ taints .................................................................................................................................. 24 

Figure 4.2.11 Drum nets used to assess the potential for re-capturing ‘live’ silver perch and Murray cod stocked 

into the ring tank.............................................................................................................................. 25 

Figure 4.2.12 Box grader used for grading fingerling and juvenile silver perch and Murray cod ...................... 25 

Figure 4.2.13 Raceway push gate grader used to passively grade fish within the raceway and also to crowd fish 

for harvest and transfer activities..................................................................................................... 26 

Figure 4.2.14 Fish transfer hopper used to move fish during stocking, grading, stock transfer or harvesting 

activity ............................................................................................................................................. 26 

Figure 4.4.1 Existing (E) and recommended (R) locations of aquaculture facilities and pumping infrastructure at 

Loch Eaton. ..................................................................................................................................... 40 

Figure 5.4.1 Pesticide levels in ring tank water from November 2001 until March 2003................................... 48 

Figure 5.4.2 Pesticide levels in river water from November 2001 until March 2003.......................................... 49 

Figure 5.4.3 Concentration of pesticides in muscle tissue of silver perch (Bidyanus bidyanus) maintained at 

15ºC and exposed to 1 μg/L heptachlor, dieldrin, endosulfan sulphate, chlorpyrifos, p,p-DDE, o,p- 

DDE, metolachlor, lindane and β-BHC for 96hrs then transferred to clean water for a period of up 

to 28 days......................................................................................................................................... 49 

Figure 5.4.4 Concentration of pesticides in muscle tissue of silver perch (Bidyanus bidyanus) maintained at 

25ºC and exposed to 1 μg/L heptachlor, dieldrin, endosulfan sulphate, chlorpyrifos, p,p-DDE, o,p- 

DDE, metolachlor, lindane and β-BHC for 96hrs then transferred to clean water for a period of up 

to 28 days......................................................................................................................................... 50 

Figure 6.1.1 Example of spreadsheet based decision tool ................................................................................... 55 

ix

Executive Summary 

What the report is about 

This report shows how the water infrastructure developed by the cotton industry for such large scale 

irrigation may also have potential for development of aquaculture. The introduction of an additional 

cropping opportunity may have significant economic, environmental and social benefits. It does 

however, also face several operational challenges that stem from the need to manage these water 

bodies and the farm’s other activities in a more intensive and considered fashion. 

Who the report is targeted at 

This report is targeted at irrigators who may be interested in diversifying their business by integrating 

commercial aquaculture with irrigated agriculture. It focuses on a demonstration site in the cotton 

industry in Queensland, but contains valuable information for potential investors throughout Australia. 

The report includes detailed analysis of the research undertaken on site and would be of interest to the 

Australian aquaculture industry and researchers interested in environmental impacts on Australian 

native fish. 

Background 

There are many thousands of hectares of water storage on cotton farms in Australia. Australia 

consumes approximately 22,185 GL of water annually of which about seventy percent (15,502 GL) of 

the total water used is consumed for agricultural production and approximately 11.9 per cent (or 1,840 

GL) of this is consumed by the cotton industry (Dalton, Raine, & Broadfoot, 2001). In Queensland 

cotton farmers are the second major industry user of freshwater in the State. 

The opportunity to utilise large water storage infrastructure for aquaculture is well recognised and is a 

common practice in many countries. However, the scale of these activities is often limited with largescale 

integrated agri-aquaculture being non-existent in Australia. A clear opportunity exists to utilise 

these resources, diversify farming operations, and deliver significant socio-economic benefits. 

To test this opportunity in Australia, an integrated aquaculture demonstration site at an irrigated cotton 

enterprise, ‘Loch Eaton’, 14 KM south of Dalby on the Darling Downs in Queensland was used. The 

development of the aquaculture enterprise was managed by the farm operators, McVeigh Brothers Inc. 

as were the farm’s irrigation activities and chemical spray events. 

The aquaculture trial screened a number of native fish species for their suitability to culture conditions 

in the farm’s existing on site cotton irrigation water storages or ‘ring tanks’, which are common to the 

area. These storages received water by pumping riverine flows and also from the farm’s groundwater 

supplies. 

Aims 

The aim of the project was to study how aquaculture was introduced into the irrigated cotton 

enterprise. This site was used as a demonstration facility for industry and to record the progress of the 

site’s development, its challenges and potential for replication. 

Specifically the aims of the study were to: 

• Develop an integrated agri-aquaculture demonstration site in on-farm water storages typically used 

for irrigated agriculture on the Darling Downs. 

• Conduct on-farm extensive production trials using Silver and Golden Perch and intensive 

production trials using Silver Perch and Murray Cod. 

• Demonstrate the potential for improved utilisation of water resources and the resultant economic 

and environmental benefits, by developing and quantifying robust farm diversification strategies. 

• Utilise the demonstration site for practical extension activities highlighting the needs and potential 

of integrated farming systems across rural Australia. 

x

Methods used 

Assessment of the site occurred over three years and involved monitoring fish growth, stocking 

practices, pesticide events, water quality, fish health, general husbandry needs and practices. Included 

in this assessment was consideration of how the aquaculture operation impacted on the farm’s existing 

cotton operations, its management, maintenance of water resources and use of water on farm. An 

important component of this study assessed how the farm’s pesticide management practices changed 

to comply with the needs of the site’s aquaculture operations 

Results 

The results from the three seasons of site development, monitoring, trials and training exercises 

demonstrated that cotton irrigators can integrate aquaculture/irrigation operations, but only with 

careful site selection, and the appropriate level of investment and technical expertise. 

The on-farm extensive production trials using Silver and Golden Perch and intensive production trials 

using Silver Perch and Murray Cod had unsatisfactory rates of growth for commercial production 

primarily due to problems with poor water quality following significant riverine pumping events. The 

harvest of water from the Condamine River occurred typically during flow events that resulted in large 

volumes of water with high turbidity and low dissolved oxygen levels to be pumped into the ring tank 

where the aquaculture trial was situated. These events not only resulted in significant mortalities 

associated with the low dissolved oxygen levels but also served to retard growth over an extended 

period because of the longer term impacts on water quality. 

These poor fish growth rates, clearly showed that aquaculture systems used must be located in a 

storage that does not directly receive flood or tail waters. Alternatively, these systems should 

incorporate capacity to be isolated from poor quality surface waters for short periods in order to avoid 

severe fluctuations in water quality. 

The study also showed that aquaculture sites must be protected from potential pesticide spray drifts 

from adjacent cotton production. There was only one detection of a compound in fish through the 

monitoring period. This event was most likely due to an off site aerial application of pesticide that 

drifted across the ring tank. Once identified and addressed no further spray drift events were detected. 

In addition to improved on farm pesticide management practices, pesticide use within the cotton 

industry has fallen significantly since the study was implemented. Such trends are expected to 

continue as industry Best Management Practices including Integrated Pest Management strategies and 

the introduction of disease resistant seed strains continue to be adopted by the cotton industry. Overall, 

the pesticide risk from adjacent cotton production was shown to be low and manageable. 

Significantly, the study developed and refined a more cost effective in-pond floating raceway system 

suitable for intensive production in environments not specifically designed for aquaculture. Although 

initially focusing on cage culture of native fish, the floating raceway system developed through the 

course of the project provided benefits of more efficient operation and greater security of stock. This 

was due to their cost effectiveness and the improved management they offer in terms of stock 

inventory, feeding, growth and disease monitoring, predator control and harvesting. Cage systems by 

comparison proved difficult to manage and were abandoned by the operator. 

Although the raceway system proved to be a durable approach to intensive fish culture, the primary 

factor limiting the aquaculture production in ring tanks is the availability and quality of surface water. 

The raceways demonstrated an ability to hold freshwater fish at high density but growth of larger fish 

in this system still was not commercial, due to the riverine pumping event outlined above. 

The issue of whole of farm water supply during periods of drought has serious implications for the 

integrated fish/cotton farmer. During this study, water for irrigation of cotton was limited and the farm 

relied heavily on its groundwater allocations. This allowed maintenance of low levels of surface water 

within the ring tank to maintain the aquaculture operation. However, for farms without access to 

sufficient groundwater supplies the cost of maintaining surface water in ring tanks may outstrip the 

return from the aquaculture facility. Therefore, the size of aquaculture operations in cotton ring tanks 

must provide a higher return from available water supplies than is returned from an irrigated cotton 

xi

crop. This is much higher than simply the cost of producing the cotton in a given year because of the 

need to absorb ongoing costs associated with the investment into the infrastructure and machinery 

associated with the cotton operation. Therefore, in order to achieve profitable integration through 

multiple use of water storages, an aquaculture operation must not place significant demands on the 

farm’s water resources. Systems like the floating raceways used in this study enable the water depth in 

ring tanks to be lowered to a minimal depth. This is beneficial as unlike cages that require a greater 

functional water depth, the raceway systems can operate in less water and therefore make more water 

available for irrigation. 

The economics of farm integration are complex as many of the inputs, resources and infrastructure are 

shared across the farm’s operations. As part of this study an Excel based spreadsheet decision tool was 

developed to assist growers investigate the potential for integrating aquaculture into their farm 

operations. Intended as a guide only, this model indicates that the demonstration farm’s overall 

profitability could be improved substantially if the documented technical and operational challenges 

faced during this study can be overcome. 

Implications and Recommendations 

It is clear from this study that while the aquaculture potential of these regions and infrastructure is 

high, there are existing issues concerning the methods and timing of water harvesting, the species 

used, the method of farming and the associated demands on the farm operators. The level of intensity 

and scale of production must be well matched to the skill of the proponent and the available 

infrastructure. Considered placement of the aquaculture operation will determine the success of the 

operation and its ability to expand. 

In conclusion, the irrigation industry is well placed to invest in the production of additional crops from 

their available water resources and infrastructure, the cotton industry is particularly well placed 

because of its commitment to environmental management and sustainability. 

It is recommended that irrigators seeking to introduce aquaculture into their existing farming 

enterprises investigate: 

• The impact of retaining up to 3m of water within the aquaculture storage on the farms irrigated 

crops. 

• The risk associated with servicing a new and highly technical farming enterprise. 

• The cost of additional training requirements for new and existing staff. 

• The minimum size that the aquaculture enterprise must achieve compared to the capacity that 

exists within their farm infrastructure. 

• The species that is optimal for their proposed system (extensive, semi-intensive or intensive). 

• The ability of the farm to maintain water supplies indefinitely. 

xii

1. Introduction 

1.1 General Background 

Large volumes of water are harvested in southern Queensland and stored for production of agricultural 

crops. On the Darling Downs hundreds of water storage or ‘ring tanks’ have been built by irrigators to 

hold many thousands of mega litres water. The major irrigated crop in this region is cotton. In 

Queensland 2001/2002 there were 96,700 hectares (ha) planted with cotton of which 79,800ha was 

irrigated production, of this the Darling Downs accounted for a total of 44,000ha of which 28,00ha 

was irrigated (ACG, 2006). 

Australia consumes approximately 22,185 GL of water annually of which about seventy percent 

(15,502 GL) of the total water used is consumed for agricultural production of which approximately 

11.9 per cent (or 1,840 GL) is consumed by the cotton industry (Dalton, Raine, & Broadfoot, 2001). 

The cotton industry is second only to the horticultural industry in terms of value derived from the 

water resource (ABS, 2000) returning a farm gate value of approximately $613 per ML consumed 

(Dalton, et.al, 2001). 

The Australian Bureau of Statistics (ABS) reports that for 2002/2003 Australian irrigated cotton 

farmers used an average of 6.5 ML/ha of water (ABS, 2006). The cost of water in real terms is 

increasing for growers and farm diversification is becoming an increasingly important consideration 

for farmers seeking to obtain more value from their water allocations and infrastructure. As a 

consequence of the cotton industry’s access to water and associated infrastructure, opportunity exists 

to integrate aquaculture into established cotton farming operations. Successful integration would 

provide significant socio-economic benefits for cotton growers as well as a number of other rural 

industries and their communities. 

Estimates of surface water storage capacities for the Condamine River catchment (Darling Downs 

region) are as follows. There are approximately 2,679 ring tank type storages with a total surface area 

of 6,115 ha with individual storages being about 2.28 ha in size on average. Palustrine/lacustrine 

water bodies that have been converted, completely or mostly, to a ring tank or other controlled storage 

account for an additional 305 storages with a total surface area of 763 ha with individual storages 

being about 2.5 ha in size (EPA, 2006). 

Fish farming as an integrated operation with irrigated cotton production is not a new concept and has 

been successfully practised with furrow and drip schemes in the United States and Israel. Potential 

exists to incorporate the same practices on Australian farms. Existing cotton water storages or ‘ring 

tanks’ vary in size from 10 to 50 ha with depths ranging from 4 to 7 m. These storages are usually 

filled by pumping riverine and overland flows when available. In some cases, a farms groundwater 

supplies are also used to supplement surface water supplies. In assessing the potential of individual 

ring tanks for fish production not only must the location and design of the ring tank be considered but 

so must the availability, source and quality of the farms water supplies and its use of agricultural 

chemicals. 

The depth of water held in any ring tank varies in accordance with a farms irrigation schedule, river 

flows, on farm rainfall patterns, evaporation rates and seepage. The depth of most storages means that 

there is potential for stratification of the water body which can result in oxygen levels in the deeper 

portion of the storage to become depleted while the levels in surface layers remain normal. This lack 

of mixing has the potential to cause problems for aquaculture when seasonal climatic conditions cause 

the water body to ‘turn’. Such an event brings the low oxygen water to the surface and in contact with 

fish and can result in death of fish in severe cases. The risks posed to aquaculture in cotton ring tanks 

by seasonal stratification needs to be assessed and any means of mitigating its impact determined. 

The timing and path by which water enters a ring tank will be of critical importance in determining the 

quality and quantity of water available for aquaculture. Water bodies that are highly turbid (has high 

levels of suspended solids such as fine clays) and have low dissolved oxygen levels are usually 

unsuitable for fish culture. Studies on catchments with predominant agricultural developments have 

1

documented such waters types as being associated with river flow or flood events (CBWC, 2002). 

Low dissolved oxygen levels will slow fish growth, can induce stress (which leads to disease 

outbreaks) and if severe enough, will result in significant to total mortality of the farms stock. The 

optimal range for native fish culture is recommended to be 4.5 mg/L or above (PIRSA, 2003). In 

ponds specifically built for aquaculture, algal growth is managed to provide such levels of oxygen. 

However, in water bodies that receive highly turbid waters algal growth is suppressed and problems 

associated with low dissolved oxygen levels become difficult to manage. Turbidity can also result in 

sediment build up within the gills of fish and in some cases even damage the gill themselves, resulting 

in further problems associated with fish growth, disease and survival. The short and long term impacts 

of water harvesting activities on the quality of water in a cotton storage needs to be assessed in order 

to determine their potential use for commercial aquaculture. The reliability of water supplies will also 

be an issue for an aquaculture operation that is integrated with a cotton farm. Most cotton storages are 

fully utilised by growers during the cropping cycle. Water consumption per hectare of production for 

cotton consumes about 8 ML/ha, of water (Mc Veigh, 2003). This water is accessed from seasonal 

flows which in some years may not be adequate to fulfil the needs of both the aquaculture and cotton 

farming enterprises. Therefore, although the cotton industry as a whole has access to a large volume of 

water, only farms that have appropriately located water storages, reliable pumping conditions and 

adequate groundwater allocations are likely to be suitable for large scale integrated aquaculture 

development. On these farms water management practices are likely to change significantly in order to 

enable aquaculture to co-exist with traditional crops. Assessment of the commercial development of 

aquaculture on a cotton farm with a favourable layout, an adequate natural resource base and the 

necessary infrastructure support is required to demonstrate the true potential of integrated farming 

practices within Australia’s cotton industry. 

Water harvesting during periods of high riverine flow also raises the risk of exposure to agricultural 

pollutants such as pesticides that can be highly toxic to fish (Kelly & Kohler, 1997). Endosulfan, is 

one pesticide that has been widely used historically on cotton farms in NSW and Queensland to treat 

for heliothis caterpillar infestations (Constable, Llewellyn, & Reid, 1998.). Endosulfan is recognised 

as being associated with several fish kills within the Murray Darling Basin (Napier, Fairweather & 

Scott, 1998). Chlorpyrifos is also toxic to fish and has been detected in 10.5 per cent of farmed catfish 

in the Untied States of America (Wan, Santerre & Deardoff, 2000). It is the aerial application of these 

pesticides that is likely to pose the major route of contamination and therefore threat, to any 

aquaculture operation. Spray drifts of agents like endosulfan and chlorpyrifos are highly toxic to fish 

and can move up to 500 m from the point of their application (Craig, Woods & Dorr, 1998). Yet it is 

not only the short term distress and damage these agents can do to fish that is of concern to an 

integrated fish farmer. It is the possibility that these agents can also rapidly accumulate in fish tissues 

to unacceptable levels either from direct absorption from the water column or through the food chain. 

As these compounds have not been approved for use on fish, an unacceptable level is any detection of 

these compounds as this will render market fish unsuitable for sale. 

The issue of pesticide management within the cotton industry is being addressed through industry 

programs that improve the application and reduce the reliance on agricultural chemicals. This program 

is the Best Management Practices (BMP) program. The BMP program represents the industries 

commitment to reducing the impacts of cotton farming on the natural environment, its neighbours, 

workers and the wider community. The BMP program has been designed to assist growers identify 

and manage risks, design farms that minimise environmental impact, use pesticide in a safe and 

responsible manner as well as use all available options to control pests (Cotton Australia). This 

includes encouraging thus introduction of new cotton varieties that require less pesticide than 

conventional varieties. During the last decade, the use of new cotton varieties has provided a 

foundation for the rapid adoption of Integrated Pest Management (IPM) practices, which in turn have 

helped reduce overall insecticide use by 70 per cent (CRDC, 2005). The introduction of Ingard cotton 

and more recently Bollgard II, have reduced chemical use significantly. The direction of the Australian 

cotton industry towards IPM and reduced reliance on chemicals is favourable for the long term 

development of aquaculture in cotton growing regions. However, the current risks associated with 

pesticide use need to be assessed in order to understand the future benefits of changing pesticide use 

patterns on the viability of aquaculture development in cotton catchments. 

2

1.2 Objectives 

This project was undertaken to demonstrate the potential for integrating an aquaculture operation into 

an established cotton farm in Queensland. It was undertaken in collaboration with an industry partner 

McVeigh Enterprises, who were in the first stages of establishing a pilot commercial aquaculture 

enterprise at their Loch Eaton Property on the Darling Downs in southern Queensland. Specifically the 

aims of the study were to: 

• Develop an integrated agri-aquaculture demonstration site in on-farm water storages typically used 

for irrigated agriculture on the Darling Downs. 

• Conduct on-farm extensive production trials using Silver and Golden Perch and intensive 

production trials using Silver Perch and Murray Cod. 

• Demonstrate the potential for improved utilisation of water resources and the resultant economic 

and environmental benefits, by developing and quantifying robust farm diversification strategies. 

• Utilise the demonstration site for practical extension activities highlighting the needs and potential 

of integrated farming systems across rural Australia. 

3

2. Demonstration Farm 

2.1 Background 

The key objective of this project was to establish a demonstration site in collaboration with industry 

partner McVeigh Brothers P/L. The purpose of this site was to present the concept of integrated 

farming to other irrigators while providing a facility where the benefits, issues and challenges of farm 

integration could be studied in detail. The farm, ‘Loch Eaton’, is a 270 ha cotton and grains farm 

located on Grassdale Road, 14 km south of Dalby on the Darling Downs, Queensland. 

Operated by Paul and Debbie McVeigh, Loch Eaton is positioned in an established irrigated cotton 

producing area. Like many in the area the farm was originally developed for wool and beef 

production. Since the mid 1980’s the farm has been used primarily for the production of cotton, grain 

and cereal crops. At present approximately 80 per cent of the farm is used for cotton production. At 

the time of this study McVeigh Brothers P/L operated a cooperative of farms along Grassdale Road of 

which Loch Eaton was the central property. There are 4 water storage cells or “ring tanks” on this 

property all of which share one border with the riparian zone of the Condamine River which flows 

along the eastern edge of the property (Fig 2.1.1). These ring tanks have a combined surface area of 

48.6 ha. Surface water is harvested from the adjacent river when water levels are above a regulated 

height using two pumping stations according to the farm’s general pumping licence. At the first 

pumping station water is pumped directly into the storage used for aquaculture. As this first ring tank 

is filled water overflows by gravity into the adjacent ring tank until it too is full or pumping is ceased. 

The second pumping station fills the lower but much shallower (

The ring tank used for fish culture (marked with arrow on map and shown in Fig 2.1.2) is 5.5 Ha and 

is a maximum of 7m deep at its deepest point when at capacity. At capacity the ring tank holds 

approximately 385ML. 

Ring Tank used for demonstration 

aquaculture facility 

Figure 2.1.2 Layout of the McVeigh Brothers properties showing farm infrastructure 

2.2 Aquaculture Systems 

The focus at Loch Eaton was to produce an additional crop, in this case fish, using the farms existing 

water infrastructure and resources. This was to be achieved without any detrimental impact on the 

farm’s existing cotton and grains operations. As such the use of earthen ponds were considered but 

deemed inappropriate as they would significantly reduce the area available for cotton production. Not 

only would the ponds cover a significant proportion of the farm but the need to install additional 

electrical, pumping and water transfer infrastructure meant the other costs were prohibitive. 

The aquaculture operation was therefore established in the farms primary ring tank which could 

receive both surface and groundwater inputs. Initially, a combination of small nursery cages (8 m 3 ) 

and larger circular grow out cages (100 m 3 ) were installed within the storage and were serviced by a 

central walkway (Fig 2.2.3). Difficulties experienced with net cages in the ring tank led the operators 

to develop their own version of in-pond floating raceway technology (Fig 2.2.4). 

This system was released commercially by the Total Aquaculture Management Company (TAMCO) 

in 2003. Termed modular plastic raceways (MPRs) the product is a roto-moulded high density 

polyethylene (HDPE) construction which uses a bank of air uplifts at one end to drive water through 

the raceway. Water flow is evenly distributed through the unit and while the rate of water exchange is 

high the velocity of water is optimal for fish growth and removal of wastes. 

5

Figure 2.2.3 Net cages used for silver perch and Murray cod production in the ring tank at Loch 

Eaton 

Figure 2.2.4 Floating raceway system developed for intensive fish production deployed in the 

ring tank at Loch Eaton 

6

2.3 Fish Species 

Silver perch (Bidyanus bidyanus) were selected for initial trials as they are readily available from 

hatcheries as fingerlings. This species forms the majority of native freshwater fish production in 

Australia with the majority of product being sold live to markets and restaurants. Although primarily 

grown in pond systems this species has shown promise in net cages and other more intensive tank 

based production systems. 

Murray cod (Maccullochella peelii peelii) was selected because it has a demonstrated potential for 

higher density production particularly in tank systems (Gooley and Gavine, 2003). It is an emerging 

species which has a higher value than silver perch although the relative cost of fingerlings for Murray 

cod are also higher. 

Golden perch (Macquaria ambigua ambigua) is another emerging native freshwater fish. While 

hatchery production of this species is well established virtually all stock is used for recreational 

stocking activities. The primary issue for this species is the weaning of fingerlings onto artificial diets. 

Recent research by DPI&F has demonstrated successful weaning strategies and good growth 

characteristics of this species under culture conditions (Herbert and Graham, 2004ab). 

7

3. Water Use and Quality 


The opportunity to utilise large water storage infrastructure for aquaculture is well recognised and is a 

common practice in many countries. However, the scale of these activities is often limited with largescale 

integrated agri-aquaculture being non-existent in Australia. A clear opportunity exists to utilise 

these resources, diversify farming operations, and provide significant socio-economic benefits for rural 

Queensland and other areas of the country. 

In assessing the potential of a farms water infrastructure for aquaculture, the availability and quality of 

water must be considered. The origin of the water (the timing and means by which the water enters the 

water storage) will be of critical importance in determining the quantity and quality of water that will 

be used for aquaculture. 

Many factors determine the quality of water for use in freshwater fish culture. These include factors 

such as water temperature, dissolved oxygen levels, turbidity, pH and nutrient levels. Fluctuations in 

these factors will impact on the growth rate of fish or in severe instances can result in the onset of 

disease and fish death. Integrating aquaculture with an industry that relies heavily on the collection of 

riverine water, typically during flood events, poses significant challenges with respect to the 

maintenance of suitable water quality. This study aimed to monitor the changes in ring tank water 

quality over consecutive seasons in a ring tank that received water from both riverine flood pumping 

events and also from the farms groundwater supply. 

3.2 Materials and Methods 

3.2.1 Water Harvesting 

Water harvested during flow events from the Condamine River and from the farms bore adjacent to the 

ring tank events were recorded. Three pumps can be used for water harvesting (4, 12 and 16″) with the 

size of pump dictated by the height of the river. All water harvested from the river and bore was 

pumped into the aquaculture ring tank in its raw form did not receive any treatment such as settling, 

the addition of flocculants or aeration. 

3.2.2 Water Quality 

In order to monitor diurnal and seasonal changes in ring tank water quality measures of dissolved 

oxygen, water temperature and pH were recorded up to twice daily (morning and late afternoon). 

Given the variable water level within the ring tank (dependent on the amount being harvested and that 

being used for watering crops), these readings were taken as surface and bottom readings only. The 

average depth of the ring tank was also recorded. The pH was only recorded for surface waters (

Samples were collected from a central point in the middle of the dam to ensure all samples were well 

mixed and that localised effects of sampling near the aquaculture operations were avoided. A sample 

was also collected from the Condamine River adjacent to the farms pumping infrastructure. Both 

samples were immediately frozen following collection and stored at -20°C until analyses. 

Nutrient analyses were conducted on the Lachat QC8000 Flow Injection Analyser (Zellweger 

Analytics Inc. Milwaukee WI 53218) following standard methods (APHA, 1995.). 

3.3 Results 

3.3.1 Water Harvesting and Movement 

There were 11 separate water movement events from the beginning of the study period (Table 3.3.1). 

These included 7 periods where water was harvested from the Condamine River and 4 from the bore 

adjacent to the storage. 

Table 3.3.1 Source, timing and duration of water harvesting activities at Loch Eaton from 

October 2000 to February 2004 

Event Source Date Started Date Finished 

Duration 

(days) 

River pumps used 

1 Bore 27/10/00 27/11/00 31 Adjacent to ring tank 


3 River 04/02/01 10/02/01 6 4 and 12″ 

4 River 14/03/01 14/04/01 31 4″ 



7 River 28/11/01 10/12/01 12 4 and 12” 

8 River 26/02/03 02/03/03 4 4 and 12” 

9 River 07/12/03 20/12/03 13 4 and 12” 

10 River 14/01/04 28/01/04 14 4, 12 and 16″ 

11 River 03/02/04 15/02/04 12 4, 12 and 16″ 

Riverine water harvesting is an opportunistic and generally seasonal activity while pumping bore 

water occurs during periods of low rainfall. The ring tank has three different sized river pumps with 

diameters of 4, 12 and 16″ inches. These pumps are activated when water levels rise to a height that 

permits their use. Not all of this pumping capacity was used for each of the recorded pumping events. 

For riverine pumping activities lasting longer than 14 days only the 4″ pump was used. Pumping 

activity lasting 14 days or less used a combination of 4, 12 and 16″ pumps. In early February 2001 a 

short term pumping event lasted for six days using both the 4 and 12″ pumps. Another more prolonged 

pumping event occurred one month later and lasted 31days. The last riverine pumping event occurred 

in late November 2001 and lasted for 12 days. After this event, no riverine water harvesting activities 

took place for over 14 months (443 days). This event was brief as water levels only permitted pumping 

to occur for a total of 4 days. Late in 2003 water levels within the ring tank had fallen to less than 30 

per cent of its capacity and all other storages on the farm were fully drained. As a consequence the 

next three pumping events, December 2003, January 2004 and February 2004 represented a period of 

significant water exchange and turnover within the ring tank. The two smaller pumps (4 and 12) were 

used for 13 days during the December 2003 event while all three pumps (4, 12 and 16″) where used 

for a total of 39 days in January and February 2004. 

In Dalby the highest rainfalls typically occur from November through to February with December 

having the highest average total monthly falls of 95 mm (AGBOM, 2005). The annual rainfall average 

for the Dalby region is 676 mm (AGBOM, 2005). Despite an increased reliance on the farms 

groundwater allocation during this study due to extended periods of little to no riverine pumping 

activity, the majority of the farms water needs were met from riverine supplies harvested during high 

flow events. Water pumped into the ring tank during these events was typical of flood waters for 

9

inland Australia with high levels of suspended sediments and low levels of dissolved oxygen. Other 

small fish and debris were also introduced to the ring tank during water harvesting activities. 

Unlike riverine water, the groundwater that was pumped into the ring tank was of high quality and 

contained no particulate or suspended matter. The volumes of bore water added to the ring tank did not 

appear large enough to influence ring tank water quality. 

Of the water harvested from the Condamine River, virtually all passed through the aquaculture ring 

tank before being transferred to other on-farm storages. Water can be drained from the aquaculture 

ring tank via a gate valve into an adjacent head ditch that can be used to irrigate adjacent fields or the 

water can be moved to the lagoon dam. This drainpipe draws directly from underneath the aquaculture 

infrastructure (cages/raceways). The ring tank can also overflow into the adjacent cell which again is 

set up to move water either to the lagoon dam or the irrigation head ditch. 

3.3.2 Water Quality 

3.3.2.1 Dissolved Oxygen 

Flood harvesting events were the most influential factor governing the variability in dissolved oxygen 

(DO) levels. The ring tank morning DO levels for surface water (SF) in January 2001 averaged 9.21 ± 

0.61mg/L (Table 3.3.2). On the 04/02/01 a major riverine pumping event commenced. At the end of 

this 10 day pumping event the morning SF DO levels had fallen to just 3.5 mg/L. They remained 

below 5 mg/L until the 23/02/01 after which they began to slowly rise reaching an average of 6.50 ± 

1.09 mg/L in May. 

In late 2001 a series of riverine and bore pumping events that occurred between the 15/11/01 and the 

10/12/01 were again associated with a decrease in ring tank DO levels. The average morning SF DO 

level was 7.14 ± 0.48 mg/L for the month prior to the first 4 day riverine pumping event. Two 

subsequent riverine pumping events on the 20th and 28th of November lasted two and six days 

respectively. These riverine pumping events also coincided with bore water pumping activity on the 

11th and the 22nd of the same month. The morning SF DO level for the week following this series of 

pumping events averaged 4.53 ± 0.54mg/L. 

For an extended period between the 10/12/01 and the 26/02/03 there were no riverine pumping events. 

In early December 2003 a pumping event lasting 13 days resulted in an immediate drop in SF DO 

levels. The morning DO level in SF waters In November 2003 averaged 5.23 ± 0.95 mg/L compared 

to the December average of 3.83 ± 1.34 mg/L. The lowest morning DO level observed during the 

pump event in December was 1.92 mg/L on the 16/12/03. Low DO levels were maintained in January 

and February 2004 with another two pumping events. The January, February and March 2004 morning 

SF DO levels averaged 3.22 ± 0.33, 3.02 ± 0.38 and 4.08 ± 0.79 mg/L respectively. Afternoon DO 

levels for these months were similar and averaged 3.41 ± 0.42, 3.38 ± 0.42 and 4.23 ± 0.58 mg/L 

respectively. 

In contrast to riverine pumping events, isolated bore water pumping events were not associated with 

any decrease in ring tank DO. A 31 day bore pumping event that commenced on the 27/10/00 was not 

associated with any fall in DO levels. The morning surface DO levels prior to this pumping activity 

averaged 9.54 ± 0.77 mg/L. The DO concentration during this pumping event averaged 9.13 ± 

0.69 mg/L and was 8.2 mg/L the day after pumping ceased. Similarly a 12 day bore pumping event 

that commenced on the 12/09/00, also had no detrimental impact on ring tank DO levels. The morning 

surface DO level in the ring tank on the 24/09/00, the day after pumping ceased, was 8.39 ± 

0.17 mg/L. This compares favourably with the DO levels observed in surface waters in the week prior 

to this pumping event which averaged 9.07 ± 0.46 mg/L. Similar observations were made for DO 

levels following bore pumping events on the 12/09/01 and the 15/11/2001. 

10

Table 3.3.2 Average monthly morning surface (SF) and floor (FL) dissolved oxygen levels 

(mg/L) in the aquaculture ring tank from November 2000 to March 2004 (mean ± standard 

deviation) 

Month 

2000 2001 2002 2003 2004 

SF FL SF FL SF FL SF FL SF FL 

January 

9.21 8.56 6.34 5.45 6.50 4.20 3.22 3.00 

±0.61 ±0.84 ±0.65 ±0.73 ±1.33 ±1.77 ±0.33 ±0.35 

February 

4.58 3.28 6.67 4.75 6.27 4.58 3.02 2.62 

±1.17 ±0.67 ±0.55 ±0.87 ±1.14 ±1.13 ±0.38 ±0.48 

March 

4.73 3.68 7.09 5.16 5.85 4.83 4.08 3.85 

±0.66 ±1.45 ±0.58 ±1.47 ±0.99 ±0.97 ±0.79 ±0.78 

April 

5.77 5.12 6.17 5.44 6.39 4.62 

±0.32 ±0.59 ±0.39 ±0.50 ±1.29 ±0.87 

May 

9.18 6.50 6.08 7.00 6.51 6.66 5.49 

±0.41 ±1.09 ±1.13 ±0.46 ±0.61 ±0.71 ±1.13 

June 

10.13 8.29 8.01 7.74 6.84 7.49 6.43 

±1.06 ±0.43 ±0.44 ±0.73 ±0.85 ±0.84 ±1.35 

July 

10.35 9.95 9.63 9.44 8.54 7.43 8.05 7.45 

±0.22 ±0.27 ±1.02 ±1.05 ±0.54 ±0.55 ±0.77 ±0.65 

August 

11.35 10.55 9.22 8.80 8.04 6.87 7.29 6.62 

±0.21 ±0.35 ±0.70 ±0.60 ±0.84 ±0.59 ±0.92 ±0.87 

September 

10.09 5.85 8.87 8.33 5.92 4.95 6.18 5.14 

±0.80 ±2.33 ±0.52 ±0.74 ±0.69 ±0.63 ±0.59 ±0.75 

October 

9.48 8.32 7.36 6.10 6.34 4.22 4.93 3.67 

±0.58 ±0.99 ±0.50 ±0.79 ±0.76 ±0.93 ±0.65 ±1.33 

November 

9.03 7.78 5.92 5.38 6.27 2.98 5.23 4.02 

±0.59 ±1.24 ±0.92 ±0.88 ±0.45 ±0.58 ±0.95 ±1.57 

December 

8.65 7.64 4.78 4.50 6.61 3.53 3.83 2.95 

±0.35 ±0.95 ±0.96 ±1.04 ±0.71 ±1.58 ±1.34 ±1.10 

Average differences in the morning surface and bottom dissolved oxygen levels in the ring tank was 

1.14 ± 1.25 mg/L over the duration of this study. The difference in the average afternoon surface and 

bottom DO levels was 1.64 ± 1.78 mg/L. The only extended period where pronounced differences in 

surface and bottom DO levels were observed were over summer months from October through to 

March in both 2002 and 2003. In both years these differences were greatest for afternoon readings. 

During this period, the afternoon surface water DO levels averaged 7.85 ± 2.04 mg/L compared to the 

bottom readings that averaged 3.97 ± 1.37 mg/L. This equates to an average difference in the daily 

surface and bottom DO levels of 3.85 ± 2.39 mg/L. Although low over summer, the DO levels at the 

floor of the ring tank increased from 4.73 ± 1.06 mg/L in March 2003 to 4.98 ± 0.78 mg/L and 5.73 ± 

1.24 mg/L in April and May respectively of that year. 

Afternoon DO levels followed the same pattern as morning DO levels but afternoon values were 

typically higher than those observed in the morning (Table 3.3.3). In 30 of the 41 months where 

comparisons were possible, the surface DO levels were higher in the afternoon than in the morning. 

The FL readings for DO in the afternoons were only higher than the morning values in 16 of the 41 

months. 

3.3.2.2 Water Temperature 

Average water temperatures fluctuated on a seasonal basis peaking in the months of January and 

February of each year. The highest observed water temperature was 33.1ºC recorded in surface waters 

in the afternoon of 15/01/04. February 2004 had the highest average monthly morning and afternoon 

surface temperatures with values of 27.22 ± 1.50 ºC and 29.30 ± 1.66 ºC (Table 3.3.4 and 3.3.5). 

July and August were the coldest months in this study. The coldest temperature of 10.5ºC was 

recorded in the surface waters and the floor of the ring tank on the 07/0702. In that month the morning 

surface and floor water temperatures averaged 11.11 ± 0.49 ºC and 10.98 ± 0.40 ºC. These were the 

lowest average monthly water temperatures recorded in this study. 

11

Table 3.3.3 Average monthly afternoon ring tank surface (SF) and floor (FL) dissolved oxygen 

levels (mg/L) from November 2000 to March 2004 (mean ± standard deviation) 

Month 

January 

February 

March 

April 

May 

June 

July 

August 

September 

October 

November 

December 

2000 2001 2002 2003 2004 


9.91 9.01 6.08 5.19 9.75 3.79 3.41 2.93 

±1.33 ±2.07 ±0.87 ±0.75 ±1.65 ±2.07 ±0.42 ±0.44 

6.43 3.06 6.37 4.62 8.63 4.83 3.38 2.62 

±1.87 ±0.81 ±0.47 ±0.83 ±2.31 ±1.29 ±0.42 ±0.49 

5.52 3.58 6.76 5.01 8.25 4.73 4.23 3.81 

±0.82 ±1.41 ±0.52 ±1.27 ±1.63 ±1.06 ±0.58 ±0.71 

6.19 5.00 5.78 5.02 7.56 4.98 

±0.39 ±0.54 ±0.49 ±0.62 ±1.37 ±0.72 

6.70 6.10 7.27 6.41 7.68 5.73 

±1.04 ±1.22 ±0.53 ±1.00 ±1.20 ±1.24 

8.27 7.87 7.97 6.84 8.39 6.28 

±0.43 ±0.30 ±0.50 ±0.91 ±0.97 ±1.14 

9.66 9.82 8.71 7.68 8.77 7.27 

±1.07 ±1.65 ±0.53 ±0.50 ±1.01 ±0.72 

9.03 8.79 8.37 7.14 7.94 6.78 

±0.63 ±0.63 ±0.92 ±0.85 ±1.14 ±0.93 

8.57 7.97 5.90 4.98 6.72 5.27 

±0.60 ±0.90 ±0.64 ±0.58 ±0.52 ±1.02 

7.21 6.04 5.92 4.16 5.57 3.63 

±0.44 ±0.66 ±0.72 ±0.80 ±0.76 ±1.13 

9.04 7.03 5.94 5.24 6.72 2.88 6.62 3.67 

±0.39 ±1.48 ±0.97 ±0.66 ±0.82 ±0.62 ±1.63 ±1.45 

9.02 8.00 4.77 4.44 7.89 3.34 4.69 2.72 

±0.38 ±1.02 ±0.98 ±0.98 ±2.02 ±0.61 ±2.65 ±1.38 

Table 3.3.4 Average monthly morning ring tank surface (SF) and floor (FL) water temperatures 

from November 2000 to March 2004 (mean ± standard deviation) 

Month 

January 

February 

March 

April 

May 

June 

July 

August 

September 

October 

November 

December 

2000 2001 2002 2003 2004 


25.97 25.64 24.97 24.56 25.12 24.77 26.70 26.60 

± 1.23 ± 1.00 ± 0.59 ± 0.44 ± 0.70 ± 0.64 ± 0.60 ± 0.58 

24.68 24.17 25.02 24.28 24.66 24.30 27.22 27.06 

± 0.71 ± 0.52 ± 0.82 ± 0.37 ± 1.11 ± 0.92 ± 1.50 ± 1.46 

24.00 23.74 23.46 23.05 23.64 23.48 24.93 24.85 

± 0.64 ± 0.41 ± 0.71 ± 0.38 ± 0.69 ± 0.65 ± 1.42 ± 1.49 

20.81 20.70 20.65 20.62 21.97 21.80 

± 0.80 ± 0.83 ± 0.48 ± 0.46 ± 1.68 ± 1.53 

17.60 19.60 17.61 17.52 17.24 17.13 18.04 17.94 

± 2.39 ± 2.08 ± 2.06 ± 1.83 ± 1.77 ± 1.04 ± 1.08 

13.40 15.07 14.91 14.14 14.03 15.53 15.31 

± 0.53 ± 1.18 ± 1.07 ± 0.64 ± 0.61 ± 1.13 ± 1.03 

13.32 12.98 13.85 13.73 11.11 10.98 14.27 14.12 

± 0.59 ± 0.48 ± 1.83 ± 1.73 ± 0.49 ± 0.40 ± 0.68 ± 0.72 

14.45 14.10 13.31 13.23 13.12 12.59 14.50 14.35 

± 0.07 ± 0.28 ± 0.65 ± 0.62 ± 0.60 ± 0.69 ± 1.27 ± 1.28 

20.07 17.06 16.29 15.85 16.98 16.20 17.78 17.49 

± 1.98 ± 1.45 ± 1.79 ± 1.67 ± 1.11 ± 1.22 ± 1.87 ± 1.72 

20.83 20.38 19.23 18.45 19.88 18.58 20.26 19.91 

± 0.75 ± 0.42 ± 0.75 ± 0.51 ± 1.13 ± 0.91 ± 1.09 ± 1.03 

22.22 21.61 21.17 20.70 22.41 20.46 22.43 22.17 

± 1.11 ± 1.16 ± 0.63 ± 0.57 ± 0.74 ± 0.88 ± 1.40 ± 1.43 

25.27 24.90 24.51 24.31 23.85 22.66 25.74 25.54 

± 0.56 ± 0.75 ± 0.63 ± 0.42 ± 0.73 ± 0.85 ± 1.43 ± 1.36 

12

Over the course of the study the average monthly surface water temperatures for July 2000, 2001, 

2002, 2003, and 2004 were 13.32 ± 0.59, 13.85 ± 1.83, 11.11 ± 0.49, 14.27 ± 0.68ºC respectively. In 

comparison the average monthly morning surface water temperatures for August 2000, 2001, 2002, 

2003, and 2004 were 14.45 ± 0.07, 13.31 ± 13.12 ± 0.60, 14.50 ± 1.27ºC respectively (Table 3.3.5). 

Average ring tank morning surface water temperatures were above 20ºC for 6 months in 2001 and 

2002 and 7 months in 2003. 

Variations in temperature readings between bottom and surface waters were similar although less 

severe than those for oxygen. The greatest differences between ring tank surface and floor water 

temperatures were observed in the afternoon. The differences between surface and ring tank floor 

water temperatures were up to 3.1ºC for morning readings and 7.5ºC for afternoon readings. This large 

difference between surface and floor temperatures in the afternoon is a consequence of the heating of 

the upper surface waters in the summer as opposed to any change in floor water temperatures. 

The highest afternoon water temperature of 33.1ºC was recorded on a single day in January 2004. The 

highest floor water temperature was 29.7ºC in February of the same year. The highest monthly 

averages for surface and floor water temperatures of 29.30 ± 1.66ºC and 27.19 ± 1.45ºC were also 

recorded in February 2004. 

Table 3.3.5 Average monthly afternoon ring tank surface (SF) and floor (FL) water temperatures 

from November 2000 to March 2004 (mean ± standard deviation) 

Month 

2000 2001 2002 2003 2004 


January 

27.82 25.91 26.21 24.83 28.10 25.16 28.34 26.83 

± 1.47 ± 1.11 ± 1.16 ± 0.56 ± 1.11 ± 0.82 ± 1.37 ± 0.56 

February 

28.18 24.33 26.34 24.28 26.34 24.75 29.30 27.19 

± 2.18 ± 0.52 ± 1.47 ± 0.35 ± 1.49 ± 1.01 ± 1.66 ± 1.45 

March 

25.39 23.92 24.38 23.16 25.38 23.89 25.97 25.33 

± 1.44 ± 0.39 ± 0.96 ± 0.43 ± 0.91 ± 0.62 ± 1.72 ± 1.74 

April 

22.07 20.87 21.44 20.64 23.00 22.30 

± 0.89 ± 0.83 ± 0.99 ± 0.51 ± 1.87 ± 1.70 

May 

18.29 17.63 17.32 16.94 18.76 18.02 

± 2.22 ± 1.94 ± 1.92 ± 1.71 ± 1.42 ± 1.20 

June 

15.85 14.78 14.53 14.33 16.09 15.48 

± 1.32 ± 0.71 ± 0.50 ± 0.48 ± 1.32 ± 1.08 

July 

14.25 13.52 11.88 11.26 15.02 14.35 

± 1.32 ± 1.19 ± 0.78 ± 0.50 ± 0.89 ± 0.65 

August 

14.19 13.47 13.98 12.79 15.36 14.57 

± 0.77 ± 0.29 ± 0.78 ± 0.56 ± 1.36 ± 1.32 

September 

17.84 16.09 17.83 16.49 18.62 17.73 

± 2.36 ± 1.72 ± 1.19 ± 0.94 ± 1.99 ± 1.68 

October 

20.13 18.62 21.92 19.07 21.86 20.17 

± 1.20 ± 0.64 ± 1.18 ± 0.97 ± 1.35 ± 1.08 

November 

24.16 22.27 22.09 20.79 25.26 20.86 24.63 22.30 

± 1.89 ± 0.65 ± 1.04 ± 0.71 ± 1.27 ± 0.90 ± 1.51 ± 1.56 

December 

26.47 25.16 25.31 24.61 26.57 23.26 27.63 25.77 

± 0.86 ± 0.75 ± 0.58 ± 0.33 ± 1.36 ± 0.66 ± 1.97 ± 1.30 

3.3.2.3 Turbidity 

Ring tank turbidity was clearly influenced by riverine pumping events (Fig 3.3.1). Prior to riverine 

water harvesting activities in February 2001 the secchi depth of the ring tank was >2.5 m. These high 

secchi values were as a result of filling the ring tank with water from the adjacent bore. However, as 

soon as riverine pumping of flood waters commenced secchi values dropped rapidly. The day after 

pumping activity ceased the secchi depth had reached 0.2 m. This decrease in secchi depth was clearly 

observed to be associated with an increase in fine suspended clays rather than any increase in 

phytoplankton abundance. 

The lowest secchi readings of 0.1m were observed following a series of pumping events in November 

and December 2001. The secchi value prior to commencement of pumping activity was 0.45 m. By the 

end of November secchi values had fallen to 0.25 m. In December, secchi values averaged just 0.11 ± 

13

169 

165 

161 

157 

153 

149 

145 

141 

137 

133 

129 

125 

121 

117 

113 

109 

105 

101 

97 

93 

89 

85 

81 

77 

73 

69 

65 

61 

57 

53 

49 

45 

41 

37 

33 

29 

25 

21 

17 

13 

9 

5 

1 

0.02 m. This change in turbidity was again due to the levels of suspended clay particles as occurs 

during riverine flow events in the Condamine River. Secchi values did not subsequently return to the 

pre November 2001 pump event values until January 2003. 

Because riverine pumping was the most significant form of water supply to the ring tank, secchi 

depths remained between 0.1 and 0.6 m for the remainder of the study. The average secchi depth after 

the February 2001 riverine pump events was 0.35±0.13 m. 

2.6 

2.4 

2.2 

2 

1.8 

Secchi Depth (m) 

1.6 

1.4 

1.2 

1 

0.8 

0.6 

0.4 

0.2 

0 

Week 

Average Secchi Depth 

Figure 3.3.1 Daily turbidity readings for the aquaculture ring tank from January 2001 to March 

2004 reported weekly. The red dashed line indicates a major riverine pumping event 

3.3.2.4 pH 

Little variation was observed in monthly pH readings in surface waters with daily averages ranging 

between 7.11 and 8.75 over the course of this study. This included little diurnal variation in pH with 

morning and afternoon pH values varying less than 0.5 pH units. The morning and afternoon pH 

values averaged 7.95 ± 0.50 and 8.05 ± 0.50 respectively for the period from December 2001 to 

January 2003. 

3.3.2.5 Background Nutrient Levels 

Monitoring of total Kjeldahl N and P in both the river and the ring tank indicated that there has not 

been any detectable effect of the aquaculture activities on water quality (Fig 3.3.2). The only clear 

differences were obtained in riverine waters prior to the February pumping event where total N and P 

levels were comparatively higher than ring tank levels. During this same period the ring tank was 

filled from underground water source as prolonged dry conditions prevented flood harvesting and as 

such had visibly better water quality. Low riverine flow that preceded the high flow event is indicative 

of poorer riverine water quality at the time, as reflected in the observed result. 

14

Figure 3.3.2 Total Kjeldahl Nitrogen (TKN) and Total Kjeldahl Phosphorous (TKP) in the 

Condamine River and Loch Eaton ring tank waters. The red dashed line indicates a major 

pumping event 

3.3.3 General Observations 

Any variability in the quality of water within the ring tank was largely associated with riverine 

pumping events that introduced water with high levels of clay turbidity and low levels of dissolved 

oxygen. Water introduced from bore supplies did not negatively influence water quality and indeed 

may have served to mitigate the impacts of riverine waters harvested in early and late 2001. 

During the summer (November to March) of 2001/2002, 2002/2003 and 2003/2004 enough water was 

harvested from high flow events from the Condamine River to result in a net exchange of waters from 

the aquaculture ring tank of up to 4 times its volume. 

Ring tank water depth varied throughout the year depending on the amount of water being harvested 

and that which was required for irrigation. In 2002 and 2003, the lack of opportunity to harvest 

riverine water resulted in relatively low water levels being maintained within the aquaculture ring tank 

for an extended period. While this water was maintained the other storages on farm were emptied. In 

late 2003 and early 2004 the harvest of large volumes of riverine water, combined with relatively low 

water levels within the ring tank resulted in a large flushing event. The low DO levels in riverine water 

and the high levels of suspended solids reduced water quality and resulted in a significant stress event 

for fish which resulted in significant stock losses (Refer to Chapter 4). 

3.4 Discussion 

Water quality within the ring tank was detrimentally affected by water harvesting activities during 

periods of high river flows. Twice during this study a series of riverine pumping events were 

responsible for introducing large volumes of ‘run off’ water into the aquaculture ring tank. Surface 

waters that drain into rivers during storm events typically carry high levels of plant matter, bacteria 

and dissolved organic matter that has been leached from soils and vegetation. These waters are also 

generally high in turbidity resulting from suspension of fine clay particles. The resulting impact on 

water quality in the ring tank was both immediate and lasting with fish mortality, reduced feeding and 

poor growth the observed outcomes. 

15

In February 2001, enough water was harvested from the river to result in a net exchange of waters 

from the aquaculture ring tank of up to four times its volume. The water itself was not only low in 

dissolved oxygen (DO) but it also carried high levels of suspended solids that dramatically increased 

the turbidity of the ring tank. Morning DO readings prior to the February 2001 pumping event 

averaged between 7.6 and 9.5 mg/L. After pumping the dissolved oxygen level fell to 3.9 mg/L. It was 

not until late May that DO levels returned to levels of above 7 mg/L. In late 2003 and early 2004, a 

series of pumping events again had a severe impact on the DO level within the ring tank. While no 

sub-lethal oxygen values are available for silver perch, it is generally accepted that this species can 

handle DO levels approaching 2 mg/L for short periods. In this study, the lowest DO reading of 

1.92 mg/L was recorded during pumping activity in late December 2003. Signs of stress in fish 

associated with low dissolved oxygen levels include loss of appetite, lethargy, congregation near 

aerators or in flowing water, gasping near the surface and mortality (Rowland and Bryant, 1995). 

These signs were observed by farm staff in late 2003 early 2004 when fish mortality was observed 

during pumping activity. Rowland and Bryant (1995) recommended that DO levels be maintained at 

concentrations of 3 mg/L or higher for silver perch in pond culture. Critical DO levels required for 

warmwater fish have been reported to be about 5 mg/L (Boyd, 1990). The lowest monthly average SF 

DO level of 3.08 ± 0.34 mg/L was obtained in the morning in February 2004. 

Prior to riverine pumping activity in 2001 the turbidity of ring tank water was low with secchi depths 

in excess of 2.5 m. However after pumping this secchi depth was reduced to less than 0.2 m. While a 

degree of clay turbidity can prevent the formation of strong phytoplankton blooms, high levels of 

turbidity can be detrimental in fish culture. Phytoplankton growth in pond culture is beneficial as 

photosynthesis adds oxygen to the water during the day while at the same time algae consume 

ammonia produced by the fish. However, high levels of clay turbidity can have a detrimental impact 

on phytoplankton populations, oxygen consumption and oxygen production within the water column. 

The introduction of large volumes of highly turbid waters will first cause a ‘die back’ or ‘crash’ of 

plankton numbers. Algal crashes in pond aquaculture can contribute significantly to the biological 

oxygen demand (BOD) of the water body as dead plankton decomposes. At the same time as the algal 

die off is consuming oxygen, photosynthesis from surviving phytoplankton in this water is reduced as 

light penetration becomes limited to the top few centimetres of the water body. 

High levels of suspended sediments can be lethal to fish (Koehn & O'Connor, 1990). High 

concentrations of clay particles can cause gill clogging in fish and in severe cases, can result in gill 

damage. Any irritation to gill tissue can increase a fish’s susceptibility to bacterial gill disease by 

causing excessive gill mucus production, epithelial hyperplasia and hypertrophy. The net result of 

irritation, disease and damage is reduced efficiency of oxygen uptake and poor growth. In 

circumstances where low DO levels exist in combination with high levels of clay turbidity even mild 

gill clogging can result in significant levels of fish mortality. 

Flocculation using gypsum and aluminium sulphate (AlSO 4 ) can be used in pond aquaculture to 

remove excessive clay turbidity and permit algal growth. Aluminium sulphate added at a dose of 

between 15 and 30 mg/L will effectively remove clay turbidity from the water column while gypsum 

must be added at concentrations between 100 and 300 mg/L (Hargreaves, 1999). Both treatments can 

be temporary as they do address the source of the turbidity which at any time may be reintroduced to 

the ring tank with further pumping or resuspended with strong wind activity and sediment disturbance. 

The optimal pH range for silver perch culture is the same as for other warm water freshwater fish and 

should be maintained between 6.5 and 8.5. In this study the afternoon pH of surface waters changed 

little indicating a low level of algal productivity due to high levels of clay turbidity. Strong algal 

blooms are often accompanied by large diurnal swings in pH. Algae consume carbon dioxide during 

photosynthesis which reduces the buffering capacity of the water and increases the pH. High pH 

values (>10) should be avoided as they can have sub-lethal effects such as gill and eye (corneal) 

damage. In pond culture the addition of a carbon source to promote bacterial growth and reduce algal 

densities through competition for nutrients is one way of managing pH. Another more common 

method is water exchange which thins out the algal bloom and reduces pH. Both these methods are 

unlikely to be practical in ring tank aquaculture where water exchanges cannot easily be implemented 

and where carbon additions may be expensive because of the volume of water requiring treatment. The 

16

management of clay turbidity using flocculants in ring tanks must therefore consider that such activity 

may stimulate problematic algal blooms in a system where new water may only be introduced on a 

seasonal and opportunistic basis. 

Average ring tank water temperatures were typically seasonal with summer temperatures reaching 

27.4ºC and winter temperatures reaching 13ºC. Water temperatures were below 20ºC for 6 months 

from May to October in 2001. Optimum temperature for silver perch culture has been reported in the 

range of 23 to 28°C with rapid growth when temperatures exceed 20°C (Rowland and Bryant, 1995). 

Reduced growth does occur at temperatures below 20°C but no substantial growth has been recorded 

lower than 13°C (Barlow and Bock 1981). At optimum temperatures it would be expected for perch to 

reach market size in 12 - 24 months. 

Differences in both surface and ring tank floor measures of DO and temperature indicate that 

stratification of the ring tank was greatest in the afternoons during summer. Stratification occurs when 

sunlight heats the surface layers of the water body making them less dense. These upper layers of 

warmer water serve to trap cooler more dense water underneath. This effect is most evident in the 

afternoon when surface water is heated by the sun but at night these surface layers cool and mix with 

deeper waters reducing the degree of stratification. Thermal stratification also prevents mixing 

between highly oxygenated surface layers and deeper water resulting is marked differences in DO 

levels. The largest difference between the average surface and bottom DO in this study was 5.96 mg/L 

for afternoon readings in January 2003. While average DO readings in deeper water were 

comparatively lower than surface waters the stratification was not severe enough to constitute an 

immediate threat to the aquaculture operation. In severely stratified water bodies the deeper waters are 

completely depleted of oxygen. During storm events stratification can be broken and these deeper 

oxygen depleted waters become mixed with the shallow oxygenated surface layers. Often referred to 

as a ‘turnover’ event, the resultant reduction in the water bodies surface oxygen levels can result in 

significant, if not total, stock losses. 

The low concentration of DO at the bottom of the ring tank indicates that either there is some mixing 

occurring within the storage or the BOD in deeper waters was at the time insufficient to fully deplete 

available oxygen. The large surface area (4 ha) of the ring tank is likely to facilitate some level of 

regular mixing of water layers but it is unlikely to result in complete mixing of the entire storage on a 

continuous basis. It is likely that as the aquaculture activity continues, the accumulation of organic 

wastes in the ring tanks sediments will deplete available oxygen in deeper waters and increase the 

risks associated with a turnover event. Therefore, any determination of the aquaculture potential of a 

ring tank like that at Loch Eaton must consider the long term impacts of management regimes on the 

sediments. One management option is rotation of the area used for culture in line with fallowing 

principles used in sea-cage culture. Moveable production systems such as cages and floating raceways 

would enable fallowing but do not serve to break up the stratification itself. Mechanical 

destratification by means of upwelling or downwelling units should be considered when stratification 

becomes severe. 

Riverine pumping during periods of high flow are an essential means of securing water supplies for 

many cotton farmers and other irrigators in Queensland and New South Wales. This type of water 

harvesting is often opportunistic and is dictated by seasonal rainfall and river flow conditions. 

Pumping this water into the aquaculture ring tank in its raw form clearly had a negative impact on ring 

tank water quality to the extent that the conditions at times were unsuitable for intensive aquaculture. 

Using an alternative storage or modifying the existing pumping infrastructure, will enable low quality 

water to be first be directed into other storages, rather than passing through the aquaculture storage. 

This would reduce the impact of flood harvesting on water quality, enable controlled exchanges 

through the aquaculture storage and reduce the cost of treating clay turbidity by reducing the total 

exchange of water through the aquaculture ring tank. With respect to the Loch Eaton site, relocation of 

the aquaculture facility to the adjacent ring tank would achieve these outcomes. 

17

4. Production Systems and Growth 


The physical and operational issues faced when developing aquaculture in non-specific water bodies 

are often significantly different from those encountered when using specifically designed aquaculture 

ponds. Net cages are the most common form of culture in large reservoirs. However, extensive 

stocking of fingerling in reservoirs is also common where a managed fishery approach is used to 

harvest the stock. In Australia most aquaculture is undertaken on an intensive basis. Net cages are used 

in the barramundi industry, especially in the fingerling and juvenile phases, to help separate size 

classes, improve general husbandry practices, reduce bird predation and manage cannibalism in 

carnivorous species such as barramundi. Ring tanks are typically high walled structures which when 

full can be as deep as 7 m. Net cages can potentially operate effectively within this type of water 

infrastructure if water levels are maintained. Another option for intensive production is raceway 

culture. Floating raceway systems have been shown to be more cost effective than cage operations as 

they can operate at higher densities within a much smaller area with less labour (Yoo, Masser & 

Hawcroft, 1995 and Masser & Lazur, 1997). At Loch Eaton both net cage and floating raceway 

systems were used at different times of the farms development. The objective of this study was to 

monitor the farms use of these systems to determine which best suit the ring tank environment. This 

monitoring included assessing the growth, survival and food conversion rate (FCR) in both cages and 

raceways. A third objective was to assess the viability of extensive stocking of ring tanks might play in 

the development of aquaculture in cotton farm water storages. 


4.2.1 Production Systems 

Three types of production system were employed in this study. Net cages were the first production 

system to be used on-farm and were established prior to commencement of this study. The second 

system, a floating raceway system, was in development during this study but by midway through the 

exercise it was the main production system used. The use of extensive stocking was also investigated 

in this study but this was not a major focus of the study. 

4.2.1.1 Cages 

Small 8 m 3 cages (Fig 4.2.1) were used for both silver perch and Murray cod juveniles while larger 

100 m 3 cages were used for silver perch juveniles and adults (Fig 4.2.2). All cages were covered in 

bird netting to reduce predation. Silver perch fingerlings supplied by commercial hatcheries were 

either stocked into a series of 10 t HDPE tanks or stocked directly into cages within the ring tank. The 

8 m 3 cages used for fingerlings were a 5 mm knotless mesh while two sizes of mesh, a 10 mm and 

20 mm, were used for the larger 100 m 3 nets. Fish in tanks were stocked at a rate averaging less than 

5 kg/m 3 . Water to the tanks was supplied on a flow through basis at ambient temperatures following 

degassing in a 20 m 3 header tank. Fingerlings were stocked into net cages at an initial rate averaging 

1,000 fish/m 3 but not exceeding 1,375 fish/m 3 . Fish were graded and restocked as dictated by growth 

and stocking strategies. 

4.2.1.2 Raceways 

The initial plastic raceways were fabricated from HDPE sheets and rotomoulded boxes welded 

together to form 7 and 14 m 3 raceways supported by plastic floats (Figs 4.2.3 and 4.2.4). The 

rotomoulded raceway was developed by Paul McVeigh in conjunction with Total Aquaculture 

Management Company (TAMCO) (Fig 4.2.5). 

18

Figure 4.2.1 Net cages 8m 3 used for silver perch and Murray cod fingerlings and juveniles 

Figure 4.2.2 Net cages 100m 3 used for silver perch grow out 

19

Figure 4.2.3 The first 7m 3 floating plastic raceway being stocked with silver perch fingerlings at 

Loch Eaton 

Figure 4.2.4 The first 14m 3 floating plastic raceways were constructed from HPDE sheets 

welded to rectangular pontoons that provided buoyancy 

20

Figure 4.2.5 The first 12m 3 TAMCO roto-moulded raceways in use at Loch Eaton 

Figure 4.2.6 A bank of uplifts (100mm) drives the water exchange through each of the raceway 

units 

21

Figure 4.2.7 Uplift, baffle board and end screen of raceways 

This raceway consists of two units, the uplift unit and the body of the raceway (Fig 4.2.5). The uplift 

unit has a set of sixteen 100 mm uplift chambers which are each fed with air from the main 50 mm 

manifold. Each of the air inlet orifices are 1/8 inch diameter and are set 80 cm from the water surface 

(Fig 4.2.6). 

A baffle (or eddy) board was placed 120 cm from the water entrance and extended 20 cm from the 

surface (Fig 4.2.7). The placement of this board helps facilitate downward rather than surface water 

flow. This assists the mixing of water within the raceways while at the same time prevents floating 

feeds from washing straight out the raceway unit. The internal flow characteristics of the raceways 

were assessed using a Sontek acoustic Doppler velocimeter (Sontek Pty Ltd, USA). Figures 4.2.8 and 

4.2.9 show the difference in raceway water flows when eddy boards are utilised. In these Figures, 

Distance refers to the distance along the raceway from the airlift end; Depth refers to water depth 

within the raceway; and Flow refers to the directional flow of water in cm/second (a negative Flow 

measure indicates that water is eddying at that point and flowing back towards the airlift end). 

Raceways were covered with shade cloth (70 per cent shade rating) as either a net panel (with eyelets 

and elastic) with a screen sewn into one end to allow feed delivery or as steel framed shade with oyster 

mesh fixed on some sections to allow viewing and feeding. Oyster mesh screens at the water entrance 

and exit prevented fish from escaping and wild fish from entering the culture unit. Cod were kept in a 

combination of different size cages, raceway and tanks dependent on the number of stock on hand and 

availability of culture units. For small numbers of stock, oyster mesh cages from 1 to 0.4 m 3 were 

used. All culture units were covered with bird netting. 

22

25 

20 

15 

Flow (cm/sec) 

10 

5 

0 

-5 

-10 

110 

100 

80 

Depth (cm) 

60 

40 

20 

1 

60 

160 

260 

360 

460 

560 

660 

Distance (cm) 

Figure 4.2.8 Water flow characteristics of raceways without an eddy board 

35 

30 

25 

20 

15 

Flow (cm/sec) 10 

5 

0 

-5 

-10 

-15 

110 

100 

80 

Depth (cm) 

60 

40 

20 

1 

160 

260 

60 

360 

460 

560 

660 

Distance (cm) 

Figure 4.2.9 Water flow characteristics of raceways with an eddy board placed 120cm from the 

water entrance and extended 20cm from the surface 

4.2.1.3 Extensive Stocking 

The potential for extensive culture in ring tanks was to be assessed through deliberate stocking of 

juvenile fish followed later by recapture efforts. However, a series of large escape events involving 

both silver perch and Murray cod from net cages in the early stages and later from some raceways 

made any co-ordinated stocking activity in this study unnecessary. 

Due to the need to recapture stock as live fish, the equipment used to assess recapture of free ranging 

fish focused on the use of trap nets in the form of lift nets and drum nets. Live fish fetch a better 

market price and also can be purged in clean tanks to rid them of any off flavour taints commonly 

associated with freshwater fish (Fig 4.2.10). The lift net used was modified from an existing 40 m 3 

cage net. The drum nets were 150 mm (stretched) knotted nylon mesh nets fitted with a polystyrene 

23

float to prevent drowning of air breathing animals such as turtles (Fig 4.2.11). The drum nets were set 

along the water edge both near the aquaculture operation and at other points around the ring tank. 

4.2.2 Fish Grading and Transfer 

Grading was used to regulate size class differences in stock and to manage the stocking densities 

within individual culture units. Size class frequency was established from individual fish weights and 

lengths obtained during weekly sub-sampling activities. From each culture unit 100 animals were 

netted, anaesthetised, weighed and measured before being revived and returned to their culture unit 

(cage or raceway). 

Stock was graded manually either with conventional box graders (Fig 4.2.12) or by push gate graders 

(Fig 4.2.13). Stock was lightly anaesthetised using AQUI-S to reduce stress and reduce potential 

damage. The volume of stock being moved between culture units was measured by displacement of 

the fish biomass. Floating HDPE bins supplied with oxygen were positioned inside each of the 

receiving culture units in order to measure this displacement. No more than 100 kg of stock were 

transferred into one of these bins at any one time. Stock health and oxygen consumption were 

constantly monitored in the displacement bins. Fish were transferred into each bin using soft mesh dip 

nets and in some cases, also involved the use of a transfer hopper (Fig 4.2.14). The transfer hopper 

was fitted with a 100 mm HDPE pipe and water was supplied via a 12V submersible pump. The last 

0.5 m of the transfer pipe was fitted with a dewatering sieve. Similar practices were used for 

harvesting market sized fish where fish of the desired size were separated by grading and then 

transferred to a 1,000 L transport tank. 

Figure 4.2.10 Purging tanks (10m 3 ) supplied with degassed bore water were used to clear silver 

perch of ‘off flavour’ taints 

24

Figure 4.2.11 Drum nets used to assess the potential for re-capturing ‘live’ silver perch and 

Murray cod stocked into the ring tank 

Figure 4.2.12 Box grader used for grading fingerling and juvenile silver perch and Murray cod 

25

Figure 4.2.13 Raceway push gate grader used to passively grade fish within the raceway and 

also to crowd fish for harvest and transfer activities 

Figure 4.2.14 Fish transfer hopper used to move fish during stocking, grading, stock transfer 

or harvesting activity 

26

4.2.3 Fish Growth 

Fish growth was monitored using weekly sub-sampling data and biomass data collected during 

stocking and harvesting activities. 

4.2.4 Feeding Practices 

Fish were fed to satiation with appropriately sized feed, delivered in at least three separate rations 

daily throughout the growing season and every three days during winter months. All feeds utilised 

were commercial fish diets with protein contents between 35 and 45 per cent. Feed inputs to each 

culture unit were recorded as quantity fed on a daily basis. A combination of both floating and sinking 

feeds were used through out the study period dependent on feed size and type of culture unit being 

used in conjunction with visual observations of feeding behaviour. 

4.2.5 Systems Maintenance 

Culture units (cages, tanks and raceways) were cleaned and maintained when possible. All units were 

kept covered to prevent bird predation. Units were thoroughly cleaned and maintained prior to 

stockings and between stock movements. Raceway uplift banks and screens were cleaned as required. 

4.2.6 Disease Monitoring and Treatments 

Fish suspected of suffering from pathogen related problems were examined using wet slide 

preparations and a light microscope (Olympus). Samples of fish from units with significant observed 

mortality were analysed at the Department of Primary Industries, Animal Research Institute Veterinary 

Laboratory at Yeerongpilly Brisbane as required. 

Fish requiring treatment for pathogens were given formalin or salt baths as required. During treatment 

supplemental aeration was supplied and stock was closely monitored for signs of stress, principally 

respiratory distress, and/or incidence of moribund fish. 

4.2.7 Purging and Sale of Fish 

Fish were purged for no less than 10 days in 10t HDPE tanks supplied with bore water at ambient 

temperatures of between 12 and 28ºC. This water was exchanged twice daily and salt added 

periodically to reduce pathogen loads and reduce post handling stress. Fish were principally sold live 

or euthanased in an ice slurry and sold whole. Some were slaughtered, filleted and frozen (as a shatter 

packed product) at a commercial seafood processor and sold through a local seafood retail outlet in 

Dalby. 

4.3 Results 

4.3.1 Production Systems 

Raceway production represented the major culture unit used for production of silver perch at this site. 

The first raceway was stocked in the beginning of May 2001 and all stock was transferred to raceways 

by the end of October in 2001, after which cages were no longer used. A total of 16 raceways were in 

operation at the completion of this study (Table 4.3.1). 

27

Table 4.3.1 Number and volume of net cages and floating raceways in operation at Loch Eaton 

from September 2000 through to March 2004 

2000 2001 2002 2003 2004 

Net Cages 

8m 3 cages 6 6 (October) 0 0 0 

100m 3 cages 3 2 (October) 0 0 0 

Raceways 

7m 3 (p’type) 0 3 1 0 0 

14m 3 (p’type) 0 3 3 1 0 

12m 3 0 0 3 3 6 

18m 3 0 0 6 6 7 

24m 3 0 0 0 1 3 

A total of 161,200 Silver Perch fingerlings were stocked during the course of the study (Table 4.3.2). 

Approximately 7,500 Murray Cod fingerlings were stocked in total and a single batch of 40,000 

Golden Perch fry were stocked for weaning trials late in late November 2002. 

The reason for moving towards raceway culture included the reduction in labour required to operate 

the system, improved management of stock and improved stock security. Significant bird strike and 

net damage problems were experienced with the net cages on an ongoing basis. However, two separate 

events involving the use of an inappropriately sized screen and a damaged screen in two raceways 

holding fingerlings in 2002 and 2003 resulted in the escape of large numbers of silver perch 

fingerlings. 

Table 4.3.2 List of known stock escape events at Loch Eaton, estimated numbers of fish lost 

and the observed cause of each escape event 

Year 

Silver Perch 

Murray Cod 

Stocked Escape* Cause Stocked Escape* Cause 

2000 21,000 2,000 Net damage 637 Net damage 

2001 70,000 23,000 Net damage 4,400 3,000 Net damage 

2002 70,200 50,000 Inappropriate 3,100 

raceway screen 

2003 96,000 10,000 Damaged raceway 

screen 

2004 - - 27,000 

4.3.2 Silver Perch 

Silver perch growth was highly variable through the course of this study but was generally poor during 

and following large riverine flood harvesting activities. Due to the developmental nature of the site 

there was very little replication of stocking activities. These results are therefore a descriptive account 

of stocking activities and growth as they occurred as net cage culture was being replaced with a 

floating raceway culture system. 

4.3.2.1 Net Cages 

The average rate of growth for silver perch were highest for a period lasting from late 2000 until 

February 2001 when water quality was the best recorded in this study. Animals stocked on 7/12/00 at 

into an 8 m 3 cage (C1) at an average size of 57.8 g reached 103.6 g after 42 days (Table 4.3.3). During 

the same period fish stocked in a 100 m 3 cage (C10) at an average weight of 5.9 g reached 23.6 g. Fish 

stocked at average sizes of 9.4 g in an 8m 3 cage (C2) and 8.8 g in a 100 m 3 cage (C11) reached 

respective averages of 36.5 and 26.2 g respectively. The rates of growth for these three cages of up 

7.1 per cent per day were not subsequently emulated in this sized fish in cages or raceways for the 

remainder of this study. 

Water quality deteriorated rapidly in early February 2001 following an extended riverine harvest 

event. The cages that had performed favourably to this point continued to increase their average body 

28

weights as water temperatures approached 20ºC in late April 2001 (section 3.4). The rate of growth 

slowed during this period (Table 4.3.4) with the highest being 3.5 per cent per day for new fingerlings 

stocked at over 1000 animals/m 3 (C12). Similar results were obtained for two groups of fish, average 

weight 3.1 g and 10.3 g, stocked on the 15/02/01 and the 03/02/01 respectively. The FCR for all cages 

were high with the lowest being 1:2.6 again for fingerlings at high density (C12). 

Growth of silver perch in cages between May and early September 2001 was minimal with rates up to 

1:9.1 in the nine net cages used (Table 4.3.5). In five of the cages FCR could not be calculated because 

the average weight of fish held in these cages actually decreased during the study period. The variable 

stock retention in net cages in the period from the 02/03/01 to the 27/09/01 reflected the overall 

difficulties associated with net cage culture in 2000 and 2001. Stock retention in net cages was as low 

as 36.4 per cent in net cages which in part contributed to the high FCR values observed in many cages 

even when growth was favourable. However, stock escape alone, even if late in the culture period, 

would not entirely explain the poor FCRs observed in all cages. A total of 3,913 kg of feed was used 

for an 803 kg gain in fish biomass for the three periods presented in Tables 4.3, 4.4 and 4.5. This 

represents an overall farm FCR of 1:4.9 for net cages. With such a high overall FCR then clearly 

operator overfeeding was a factor in this study. 

Due to issues concerning stock retention in cages and difficulties associated with treating winter 

diseases, all cage culture activities were ceased by October 2001. 

4.3.2.2 Raceways 

The first 7 m 3 prototype small raceway (SR1) was stocked on the 03/05/01 with 5,784 silver perch 

fingerlings, average weight 3.2 g. This equates to an initial stocking density of 2.6 kg/m 3 (Table 4.3.6). 

At the same time an 8 m 3 net cage (C8) was stocked with another 5,744 fish from the same stock, 

average weight 3.2 g, at a density of 2.3 kg/m 3 (Table 4.3.5). After 76 days the respective average 

weights in raceway and caged fish were 3.3 and 3.6 g. A second 7 m 3 raceway (SR2) was stocked on 

the 04/07/01 with 11,255 fish (average weight 7.6 g) to give a stocking rate of 1,608 fish/m 3 or 

12.1 kg/m 3 . The average size of these fish increased to 10.5 g in 14 days. Fish of the same approximate 

size (6.8 g) stocked at the same time in an 8 m 3 net cage (C9) actually decreased in size during the 

same 14 day period (Table 4.3.5). Stock retention in both the raceways (99.8 and 98.2 per cent) and 

their comparative cages (99.5 and 98 per cent) was high. 

29

Table 4.3.3 The length of culture period (Days), number per cubic meter (N/m 3 ), initial weight 

(IW), final weight (FW), initial stocking density (ISDkg/m 3 ), final stocking density (FSDkg/m 3 ) 

and daily percentage growth (G%/day) for silver perch (Bidyanus bidyanus) held in 8 and 

100m 3 net cages from the 07/12/00 up to the 31/01/01 

Cage Start Finish Days N/m 3 IW FW ISD FSD G%/day 

(g) (g) (kg/m 3 ) (kg/m 3 ) 

C1 07/12/00 31/01/01 42 125 57.8 103. 7.2 12.9 1.9 

6 

C2 07/12/00 31/01/01 42 300 9.4 36.5 2.8 10.9 6.9 

C3 07/12/00 31/01/01 42 35.6 5.9 23.6 0.2 0.8 7.1 

C4 07/12/00 31/01/01 42 47.4 8.8 26.2 0.4 1.4 4.7 

Table 4.3.4 The length of culture period (Days), number per cubic meter (N/m 3 , initial weight 

(IW), final weight (FW), initial stocking density (ISDkg/m 3 ), final stocking density (FSDkg/m 3 ), 

percent stock retention (%SR) and daily percentage growth (G%/day) for silver perch 

(Bidyanus bidyanus) held in 8 and 100m 3 net cages from the 30/01/01 up to 26/04/01 in 8 and 

100m 3 net cages. Where FCR values are not provided their calculation had been invalidated by 

a lack of growth, reduction in biomass through stock loss or both 

Cage Start Finish Days N/m 3 IW 

(g) 

FW 

(g) 

ISD 

(kg/m 3 ) 

FSD 

(kg/m 3 ) 

C1 31/01/01 26/04/01 85 125 123.3 165.7 17.7 7.8 37.5 0.4 - 

C2 23/01/01 01/03/01 37 1375 2.9 5.9 4.0 3.6 44.5 2.8 - 

C3 31/01/01 26/04/01 85 35.8 54 114.6 1.8 4.1 100 1.3 1:3.5 

C4 15/02/01 26/04/01 70 47.4 35 91.8 1.7 4.3 100 2.3 1:3.2 

C5 30/01/01 26/04/01 86 1,063 1.3 10.6 1.4 11.2 100 3.5 1:2.6 

C6 15/02/01 26/04/01 70 612.5 3.1 8.5 1.9 5.2 100 2.5 1:4.2 

C7 02/03/01 26/04/01 55 771.3 10.3 18.4 7.9 14.2 100 1.4 1:3.6 

%SR 

G%/ 

day 

FCR 



percent stock retention (%SR) and daily percentage growth (G%/day) for silver perch 

(Bidyanus bidyanus) held in 8 and 100m 3 net cages from the 02/03/01 up to 27/09/01 in 8 and 

100m 3 net cages. Where FCR values are not provided their calculation had been invalidated by 

a lack of growth, reduction in biomass through stock loss or both 

Cage Start Finish Days N/m 3 IW FW ISD FSD %SR G% /day FCR 

(g) (g) (kg/m 3 ) (kg/m 3 ) 

C1 11/05/01 27/09/01 139 46.8 170.5 199.8 8.0 9.2 98.4 0.1 1:9.1 

C2 02/03/01 07/06/01 97 599 4.5 11.0 2.7 6.4 96.9 0.0 1:4.1 

C3 11/05/01 02/08/01 83 24 137.5 136.6 3.3 2.5 76.3 -0.0 - 

C4 11/05/01 02/08/01 83 47.4 94.6 110.9 4.48 1.9 36.8 0.2 - 

C5 11/05/01 04/07/01 54 1063 11.1 11.2 11.8 9.2 77.7 0.0 - 

C6 11/05/01 18/07/01 68 737.5 10.3 10.2 7.6 6.2 83.1 -0.0 - 

C7 11/05/01 27/09/01 139 771.3 18.1 29.6 13.9 20.8 91.0 0.5 1:1.6 

C8 03/05/01 18/07/01 76 718 3.2 3.6 2.3 2.6 99.5 0.2 1:7.3 

C9 04/07/01 18/07/01 14 896.6 6.8 6.5 6.1 5.7 98.0 -0.3 - 

30




bidyanus) from the 02/03/01 up to 27/09/01 in 7 and 14m 3 raceways 

R’way Start Finish Days N/m 3 IW FW ISD FSD %SR G%/day 

(g) (g) (kg/m 3 ) (kg/m 3 ) 

SR1 03/05/01 18/07/01 76 826 3.2 3.3 2.6 2.8 99.8 0.1 

SR2 04/07/01 18/07/01 14 1608 7.6 10.5 12.1 16.4 98.2 2.8 

On the 02/08/01 all caged fish from C8 were transferred to SR1 to give a new stocking density of 

19.1 kg/m 3 or 3,709 fish/m 3 (Table 4.3.7). The second of the small raceways (SR2) was graded on the 

02/08/01 to reduce the numbers of fish to 5,543 and give an average weight of 20.4 g at a density of 

16.0 kg/m 3 . A third 14 m 3 raceway (MR1) was also stocked on the 02/08/01 with 129.6 g fish at a rate 

of 255 fish/m 3 or 33.1 kg/m 3 . Fifty six (SR1 and SR2) and 28 days later (MR1) the average weights of 

fish in all raceways had increased only marginally to 6.0, 22.2 and 142.1 g respectively. This equates 

to a daily growth rate of 0.3, 0.2 and 0.3 per cent. Mortality in the three units was minimal and stock 

retention was equivalent to 99.2, 99.1 and 97.6 per cent of fish stocked. 

On the 07/11/01 three 7 m 3 and three 14 m 3 raceways were re-stocked (Table 4.3.8). The three 7 m 3 

raceways were stocked at rates of 1,393 (SR1), 1,453 (SR2) and 977 (SR3) fish/m 3 with fish weighing 

15.9, 5.9 and 10.4 g respectively. These raceways were operated for 83 days before being harvested. 

At harvest, the average weights had increased to 35.3, 25.3 and 22.5 g respectively. The rates of 

growth in these three raceways were 1.5, 3.9 and 1.4 per cent per day. Survival was high in all 

raceways with the lowest being 92.9 per cent (SR1). The FCRs in these three 7 m 3 raceways were 

1:1.8, 1:1.5 and 1:4.1 respectively. The three 14 m 3 raceways were stocked with 69.7 (MR1), 31.1 

(MR2) and 198.3 g (MR3) fish. The respective numbers stocked were equal to 358, 1,063 and 332/m 3 . 

Survival was again high with 100, 92 and 100 per cent of stock retained at harvest. However, growth 

in raceways over this period was variable with average weights in MR1 and MR2 increasing to 98.5 

and 77 g while the average weight of fish in MR3 decreased to 189 g. The raceway with the highest 

rate of growth of 1.8 per cent per day (MR2) also returned an FCR of 1:1.6. In comparison the other 

14 m 3 raceway with 0.5 per cent per day growth (MR1), had an FCR of 1:6.9. In the raceway with no 

apparent growth 453 kg of feed was used for a net loss of biomass. This inconsistent FCR values for 

raceways during the period from 07/11/01 to 29/01/02 indicates significant operator over feeding in 

some instances. This may have been the result of poor feeding response and/or overfeeding by the 

operator in some raceways. 

On the 05/02/02 all raceways were graded and re-stocked with various size classes of fish 

(Table 4.3.9). A number of new TAMCO raceways were also added. In the only remaining 7 m 3 

raceway (SR3), 64.5 g fish were stocked at a rate of 165/m 3 giving a density of 10.6 kg/m 3 . At the 

same time similar sized fish averaging 68 g, were stocked into a larger 14 m 3 raceway (MR2) at a rate 

of 393/m 3 or 26.7 kg/m 3 . The 7m 3 raceway was harvested after 91 days on the 07/05/02 when fish 

weight averaged 132.8 g. This represents a growth rate of 1.3 per cent per day. Stock retention was 

high with only 14 mortalities observed and 979 fish harvested. The final operating density was 

18.6 kg/m 3 . The 14 m 3 raceway was harvested after 91 days with stock averaging 135.2 g. The final 

operating density in this raceway was 53.0kg/m 3 . Survival was again high with only 19 observed 

mortalities and 4,502 fish harvested. Growth in the 14 m 3 raceways did not appear to be detrimentally 

affected by an increase in density. Similar results were observed for 137 g and 140 g fish stocked at 76 

and 168fish/m 3 in identical 1m 3 raceways (MR4 and MR6). In this case, both raceways were stocked 

and harvested at the same time (after 91 days). Fish from the lower density raceway (MR4) averaged 

216.5 g and fish in the higher density raceway (MR6) averaged 232.2 g at harvest. Stock retention and 

therefore survival was unaffected by density with 95.0 and 99.8 per cent of stock being harvested from 

the low and high density raceways respectively. 

31

Stock retention was also high in the remaining raceways (MR 1, MR3, MR5, M1) over this period 

(05/02/02 – 07/05/02) (Table 4.3.9). The lowest stock retention rate of 83.8 per cent was in one of the 

new 12 m 3 TAMCO model raceways (M1) which was stocked with 43,632 fingerlings at 1.3 g each 

(M1). 

After 65 days 33,503 fish were harvested with an average weight of 7.2 g. The low rate of stock 

retention in this raceway was the result of 3,220 mortalities that were associated with a prophylactic 

treatment given to the stock during the latter part of the culture period. In the remaining three 

raceways (MR1, MR3, MR5), fish with average weights of 13.8, 30.7 and 253 g were stocked at rates 

of 984, 883 and 90 fish/m 3 respectively. The first of these raceways (MR1) was harvested after 

76 days with fish averaging 31.3 g. The second raceway (MR3) was harvested at an after 91 days with 

61.2 g average fish while the third raceway (MR5) was harvested after 76 days with 299 g fish. Rates 

of retention were equivalent to 99.1, 99.1 and 99.2 per cent respectively for these three raceways. The 

growth rates in these raceways were 0.4 (MR1), 1.1 (MR3) and 0.2 per cent per day (MR5). 

The FCR values for all raceways were above two for the period between 05/02/02 to 07/05/02. The 

highest FCR was recorded for the raceway with the largest fish (MR5). This raceway had an FCR of 

1:8.6. For fish with an average size of 299.3 g this high FCR value indicates a high degree of 

overfeeding. This raceway had a comparatively low stocking density of 90 fish/m 3 . The other high 

FCR values of 1:6.0 and 1:4.2 were obtained in raceways stocked at 76 (MR4) and 165fish/m 3 (SR3) 

respectively. In comparison, FCRs in raceways stocked at densities of 168 fish/m 3 for 140.0 g fish 

(MR6) and 393 fish/m 3 for 68 g fish (MR2) were 1:2.3 and 1:2.1 respectively. This data suggests that 

overfeeding in raceways may be a combination of differing fish feeding behaviour associated with 

feed response and operator feeding practices. 

The growth of all size classes of fish in raceways was minimal over the winter of 2002. From the 

19/07/02 until the 21/10/02 the average growth rate of fish was less than 0.24 ± 0.59 per cent per day 

(Table 4.3.10). The highest rate of growth was recorded in fish stocked at 19.9 g at a density of 

17.8 kg/m 3 (SR2). A reduction in average weight was recorded for the raceway stocked with the 

largest fish at 41.4 kg/m 3 (MR5). The combined net weight gain for all raceways over this period was 

794kg. 

On the 06/11/02 fish from all raceways were graded and stocked into similar size classes (Table 

4.3.11). All but one of the 14m 3 prototype raceways (MR4) had been superseded with new TAMCO 

raceways. Approximately 35,410 fish averaging 4.6 g were stocked into a 12 m 3 raceway (S4) at a 

density of 2,950 fish/m 3 (13.5 kg/m 3 ). On the 18/02/02, after 104 days, these fish averaged 33.2 g and 

reached a final density of 86 kg/m 3 . This represents an average daily growth of 6.0 per cent per day. 

Good rates of growth were also observed for 12.1 and 30.2 g fish stocked in two 12 m 3 raceways at 

densities of 804 fish/m 3 (S5) and 1,068 fish/m 3 (S6). These fish reached 46.9 and 74.8 g respectively 

after 104 days growing at rates of 2.8 (S5) and 1.4 per cent per day (S6). The final densities in these 

raceways were high at 52 and 116 kg/m 3 . In all three cases (S4, S5 and S6) survival was high with 

87.6, 95 and 99.3 per cent of the stock retained. Larger fish (IW average 62.4 and 131.2g) were also 

stocked at high densities (32.3 and 69.7 kg/m 3 ) in two 17.5 m 3 raceways (M1 and M2). The lower than 

expected stock retention of 78.9 per cent in M2 was the result of mortality experienced during a single 

prophylactic treatment on the 11/12/02. 

The high retention figures assisted in achieving relatively high final operating densities of 65.3 and 

81.4 kg/m 3 . 

Fish with average weights approaching 244.7 and 296.7 g were stocked into two raceways (M3 and 

MR4) at 59.4 and 39.2 kg/m 3 (Table 4.3.11). Although some growth was recorded, these raceways 

were regularly graded to remove market sized fish and so any figures concerning average weight are 

not an accurate indication of final weights. 

The FCR for all raceways during the period from 06/11/02 to 18/02/02 ranged between 1:1.3 and 1:4.7 

(Table 4.3.11). The lowest FCR values were obtained for 4.6 (S4), 12.1 (S5) and 30.2 g fish (S6) 

stocked at densities for their size class. The FCR’s for these raceways were 1:1.3, 1:2.1 and 1:1.6 

respectively. Fish stocked with an average weight of 62.4 g (M1) returned an FCR of 1:2.1. The worst 

32

FCR value of 1:4.7 was recorded in fish stocked at an average size of 121.1 g and harvested at 193 g 

after 98 days (M2). The low survival of 78.9 per cent may have contributed to the high FCR value in 

this raceway. 



percent stock retention (%SR) daily percentage growth (G%/day) and food conversion ratio 

(FCR)for silver perch (Bidyanus bidyanus) from the 02/03/01 up to 27/09/01 in 7 and 14m 3 

raceways 

R’way Start Finish Days N/m 3 IW FW ISD FSD %SR G%/day FCR 

(g) (g) (kg/m 3 ) (kg/m 3 ) 

SR1 02/08/01 27/09/01 56 3709 5.1 6.0 19.1 22.1 99.2 0.3 1:2.9 

SR2 02/08/01 27/09/01 56 784 20.4 22.2 16.0 17.1 99.1 0.2 1:5.6 

MR1 30/08/01 27/09/01 28 255 129.6 142.1 33.1 36.3 97.6 0.3 1:1.9 



percent stock retention (%SR), daily percentage growth (G%/day) and food conversion ratio 

(FCR) for silver perch (Bidyanus bidyanus) from the 02/03/01 up to 27/09/01 in 7 and 14m 3 

raceways. Where FCR values are not provided their calculation had been invalidated by a lack 

of growth, reduction in biomass through stock loss or both 


(g) (g) (kg/m 3 ) (kg/m 3 ) 

SR1 07/11/01 29/01/02 83 1393 15.9 35.3 22.2 45.7 92.9 1.5 1:1.8 

SR2 07/11/01 29/01/02 83 1453 5.9 25.3 8.7 36.7 100 3.9 1:1.5 

SR3 07/11/01 29/01/02 83 977 10.4 22.5 10.2 22.0 100 1.4 1:4.1 

MR1 07/11/01 29/01/02 83 358 69.7 98.5 25.0 35.3 100 0.5 1:6.9 

MR2 07/11/01 29/01/02 83 1063 31.1 77.0 33.1 75.2 91.9 1.8 1:1.6 

MR3 07/11/01 29/01/02 83 332 198.3 189.0 65.9 62.8 100 -0.1 - 





raceways as well as a single 12m 3 raceway 

R’way Start Finish Days N/m 3 IW FW ISD FSD %S G%/day FCR 

(g) (g) (kg/m 3 ) (kg/m 3 ) R 

SR3 05/02/02 07/05/02 91 165 64.5 132.8 10.6 18.6 84.8 1.2 1:4.2 

MR1 05/02/02 22/04/02 76 984 13.8 31.3 13.6 30.6 99.1 0.4 1:2.9 

MR2 05/02/02 22/04/02 76 393 68.0 135.2 26.7 53.0 99.7 1.3 1:2.1 

MR3 05/02/02 07/05/02 91 883 30.7 61.2 27.1 54.9 99.1 1.1 1:2.1 

MR4 05/02/02 07/05/02 91 76 137.0 216.5 10.4 15.7 95.0 0.6 1:6.0 

MR5 05/02/02 22/04/02 76 90 253.0 299.3 22.8 26.8 99.2 0.2 1:8.6 

MR6 05/02/02 07/05/02 91 168 140.0 232.2 23.5 42.5 99.8 0.7 1:2.3 

M1 03/03/02 07/05/02 65 3636 1.3 7.2 4.6 21.8 83.8 7.2 1:1.7 

33


(IW), final weight (FW), initial stocking density (ISDkg/m 3 ), final stocking density (FSDkg/m3), 



raceways. FCR values are not provided their calculation had been invalidated by a lack of 

growth or a reduction in biomass through stock loss 

R’way Start Finish Days N/m 3 IW 

(g) 

FW 

(g) 

ISD 

(kg/m 3 ) 

FSD 

(kg/m 3 ) 

SR2 19/07/02 21/10/02 94 891 19.9 37.1 17.8 33.0 

SR3 19/07/02 21/10/02 94 1844 9.5 16.7 17.5 30.8 

MR2 19/07/02 21/10/02 94 215 72.7 98.5 15.6 21.1 

MR3 19/07/02 21/10/02 94 191 142.9 177.6 27.3 33.9 

MR4 19/07/02 21/10/02 94 764 40.9 54.9 31.2 41.9 

MR5 19/07/02 08/10/02 81 133 311.8 296.6 41.4 39.3 

MR6 19/07/02 21/10/02 94 486 76.8 94.4 37.3 45.3 

MR7 19/07/02 21/10/02 94 3428 3.8 5.6 13.1 19.3 

MR8 19/07/02 21/10/02 94 205 165.6 190.7 33.9 39.0 

MR9 19/07/02 21/10/02 94 170 284.1 294.2 48.2 49.9 

Two 12 m 3 raceways (S1 and S2) were stocked with separate batches of fingerlings averaging 2.5 and 

1.5 g on the 11/03/03 and the 25/03/03 (Table 4.3.12). In the raceway with fish averaging 2.5 g (S1) 

the stocking density was 10.9 kg/ m 3 (4,364fish/m 3 ) while the smaller 1.5 g fish (S2) were stocked at 

5.7 kg/m 3 (3,833fish/m 3 ). Both raceways were harvested on the 15/04/03 (35 and 21 days after 

stocking). The average weights of fish at harvest were 5.5 and 3.8 g respectively. This equates to a 

daily increase in weight of 3.5 and 7.5 per cent per day. In both cases stock retention was high at 97.1 

and 98.7 per cent. The low FCR in the raceway with the fastest rate of growth (S2) may indicate that 

some benefit may be obtained from the natural productivity within the ring tank. 

On the 20/02/03 an additional four 12 m 3 raceways and four 17.5 m 3 raceways were graded and 

restocked with a total of 87,390 fish at various densities and size classes. The smallest fish with an 

average weight 15.4 g were stocked at a density of 6.4 kg/m 3 or 417 fish/m 3 in one of the 12 m 3 

raceways (S3). After 33 days the average size of fish had increased to 27.1 g. The next largest group of 

fish with an average weight of 23.8 g were re-stocked into another 12 m 3 raceway (S4) at a density of 

17.9 kg/m 3 or 750 fish/m 3 . These fish reached an average of 36.6 g after 33 days with little observed 

mortality. The two remaining 12 m 3 raceways (S5 and S6) were stocked with fish averaging 48.7 and 

51.9 g at a density of 69.6 and 70.4 kg/m 3 respectively. These raceways reached final average weights 

of 71.3 (S5) and 88.9 g (S6) after 33 days. The four 17.5 m 3 raceways were stocked with 120.4 (M1), 

161.3 (M2), 246.2 (M3) and 390.6 g (M4) average fish at rates of 81, 60.6, 92.6 and 53.4 kg/m 3 

respectively. These raceways were harvested and graded again after 33 days. The average weights at 

harvest were 119.6 (M1), 173.6 (M2), 224.1 (M3) and 408.43 g (M4). Mortality rates were again low 

with stock retention rates as equalling 99.7, 99.7, 97.4 and 98.8 per cent in M1, M2, M3 and M4 

respectively. 

The widely variable FCR values observed in raceways S5 and S6 stocked at similar densities, with 

approximately the same sized fish, is an indication of operator overfeeding in response to an apparent 

poor feed response. Feed input in S5 was 401 kg for the period from the 20/02/03 to the 25/03/03 for a 

net biomass gain of just 20.7 kg. In comparison, 376 kg of feed was fed to S6 for a net gain in biomass 

of 222.8 kg. The high %SR value and lack of growth in S5 indicates that feed management practices in 

this raceway were not adjusted to suit the feed response of the stock. Similarly poor growth and high 

rates of feeding also yielded poor FCR results in all four 17.5 m 3 raceways during this period with 

1,373 kg of feed being delivered for a combined loss of 20 kg of biomass. 

With the exception of two 12 m 3 raceways that were graded and stocked on the 22/04/03 and a single 

17.5 m 3 raceway that was stocked on the 08/04/03, all fish in the remaining four 12 m 3 and the four 

17.5 m 3 raceways were graded and restocked by the 13/05/03 (Table 4.3.13). Two of the 12 m 3 

raceways (S1 and S2) were restocked for the winter period with fish averaging 3.9 and 7.2 g at 

34

densities of 13.6 and 9.4 kg/m 3 . These fish averaged 19.2 and 14.5 g respectively after 251 and 160 

days. The other two 12 m 3 raceways (S4 and S5) were left empty until being restocked on the 13/05/03 

with 18.2 and 36.2 g fish at densities of 14.8 and 17.1 kg/m 3 . These animals average 31.3 (S4) and 

72.5g (S5) after 230 and 240 days respectively representing a growth rate of 0.3 and 0.4 per cent per 

day. On the 08/04/03, 68.0 g fish were stocked at a density of 68 kg/m 3 in a 12 m 3 raceway (S6). 

These fish averaged 92.9 g after 275 days, a growth rate of 0.1 per cent day. The resulting final 

operating density was 127.5 kg/m 3 . In comparison, 61.7 g fish stocked one month later at a rate of 49.8 

g/m 3 (M1) reached a similar final average weight of 97.1 after 230 days. 

In three of the 17.5 m 3 raceways 121.6 (M2), 128.4 (M3) and 183.2 g fish (M4) were stocked at 

densities of 50.3, 52.2, and 49.4 kg/m 3 respectively. The average weights increased to 166.6 g after 

195 days (M2) and 173.3 (M3) and 257.5 g (M4) after 265 days. The final operating densities in these 

raceways were 67.1, 44.8 and 53.8 kg/m 3 respectively. In the remaining 17.5 m 3 raceway (M5), 

253.8 g fish were stocked at a density of 68.3 kg/m 3 . The average weight of fish in this raceway fell 

after 230 days to 225.9 g. The largest fish, average 357.1 g, were stocked into a 23 m 3 raceway (L1). 

The lack of growth and reduction in stocking density in this raceway was a function of high mortality 

observed in this raceway and not from harvest of market sized fish. 

A series of riverine pumping events in late 2003 and January 2004 rapidly lowered dissolved oxygen 

levels to critical levels in the ring tank. The first of these events resulted in high mortalities in a 

number of raceways including those holding market sized fish of 400 g and above. For the week 

corresponding with riverine pumping from the 07/12/03 to the 20/12/03 there were in excess of 10,000 

mortalities. Of these only 61 or just under 1 per cent occurred in the small raceways (S1 to S6) during 

or after the water harvesting events. The 23 m 3 raceway L1 was carrying the largest fish and suffered 

the highest recorded mortality of 63.1 per cent. The next highest mortality level of 36.4 per cent was 

recorded in M3. However, these figures may have been higher as accurate figures of mortalities were 

not kept by some farm staff due to the urgency of removing dead fish from the raceways. 

4.3.2.3 Extensive Stocking 

Only small numbers of market sized silver perch were re-captured using hook and line and lift net. 

These were not commercial quantities and the process of collection was labour intensive and 

unreliable. No fish were recaptured in drum nets despite over 30 days of deployment. 

4.3.3 Murray Cod 

Three separate batches of Murray cod fingerlings were received at Loch Eaton during the course of 

this study. Difficulties were experienced with all three batches of fish. These difficulties were 

associated with low numbers of stock of distinct size classes as the result of stock loss to disease and 

also stock escape. 

On the 02/03/01 two 8 m 3 net cages were stocked with a single cohort of Murray cod fingerlings. The 

first cage was stocked with 2,520 fish (average weight of 2.10 g) and the second with 1,130 fish 

(average weight 1.20 g). The growth rate of these two cages averaged 5.29 per cent per day until 

harvest on the 26/04/01. However, as with silver perch in cages, stock retention was poor with only 

2,035 of the initial 3,650 fish returned. After grading and restocking, growth was slowed over the 

winter months and averaged just 0.17 per cent per day over the next 147 days. However, this growth 

rate was severely compromised by stock escape and mortality. On the 29/09/01 only 411 of the 2,035 

fish stocked in the two net cages were harvested. These were later released into the dam as their 

numbers were insufficient to warrant further grow out effort. 

4.3.4 Golden perch 

In October 2002 a single batch of 1g golden perch fingerlings were stocked directly into one 12.5 m 3 

raceway. 

35

4.3.5 Disease Detection and Treatment 

With respect to fish health, “winter disease” symptoms associated with the presence of the 

ectoparasites Trichodina sp., Chilodonella sp., Epistylis sp. and Ichthyophthirius multifiliis were 

detected on occasion in skin and gill scrapings examined during routine health checks. Two digenean 

parasite species were found, one distinct species in Murray Cod and one in silver perch. Flexibacter 

sp. was the only bacterial pathogen detected. 

Generally pathogen outbreaks were linked to occasions where poor environmental conditions persisted 

as the result of poor husbandry practices. The incidence and severity of any outbreak in a production 

unit were reduced once these issues where addressed. 

Presence of Flexibacter sp. and its associated symptoms were found in fingerlings of both Murray Cod 

and silver perch in 2002 within 24 hrs of delivery. On both occasions appropriate treatments were 

initiated. 




(FCR) for silver perch (Bidyanus bidyanus) from the 06/11/02 up to 18/02/03 in 12 and 17.5m 3 

raceways as well as a single 14m 3 raceway. Where FCR values are not provided their 

calculation had been invalidated by a lack of growth, a reduction in biomass through stock 

loss, or a reduction in biomass from fish harvest 


(g) (g) (kg/m 3 ) (kg/m 3 ) 

S3 28/01/03 18/02/03 21 - 8.6 15.4 - - - 3.7 - 

S4 06/11/02 18/02/03 104 2950 4.6 33.2 13.5 85.9 87.6 6.0 1:1.3 

S5 06/11/02 18/02/03 104 1125 12.1 46.9 14.2 52.1 95.0 2.8 1:2.1 

S6 06/11/02 18/02/03 104 1496 30.2 74.8 47.1 115.9 99.3 1.4 1:1.6 

M1 07/11/02 18/02/03 98 518 62.4 126.6 32.3 65.3 98.9 1.1 1:2.2 

M2 07/11/02 18/02/03 98 531 121.1 193.0 64.3 81.4 78.9 0.6 1:4.7 

M3 * 18/11/02 18/02/03 69 200 244.7 307.5 59.4 61.4 ¥ 99.5 ¥ 0.4 ¥ - 

MR4 * 18/11/02 18/02/03 69 132 296.7 383.6 39.3 49.6 ¥ 99.7 ¥ 0.4 ¥ - 

* Raceways that had stock removed as market sized fish. 

¥ Final figures adjusted for numbers of fish removed for market supply. 

36




(FCR) for silver perch (Bidyanus bidyanus) from the 20/02/02 up to 25/03/03 in 12 and 17.5m 3 

raceways. Where FCR values are not provided their calculation had been invalidated by a lack 

of growth, a reduction in biomass through stock loss, or a reduction in biomass from fish 

harvest 


(g) (g) (kg/m 3 ) (kg/m 3 ) 

S1 11/03/03 15/04/03 35 4364 2.5 5.5 10.9 24.1 97.1 3.5 1:1.9 

S2 25/03/03 15/04/03 21 3833 1.5 3.8 5.7 14.5 98.7 7.5 1:0.8 

S3 20/02/03 25/03/03 33 417 15.4 27.1 6.4 11.3 99.9 2.3 1:1.5 

S4 20/02/03 25/03/03 33 750 23.8 36.6 17.9 27.5 99.9 1.6 1:2.5 

S5 20/02/03 25/03/03 33 1429 48.7 49.3 69.6 71.3 99.9 0.1 1:19.4 

S6 20/02/03 25/03/03 33 1355 51.9 65.6 70.4 88.9 99.8 0.8 1:1.7 

M1 20/02/03 25/03/03 33 673 120.4 119.6 81 80.5 99.7 -0.0 - 

M2 20/02/03 25/03/03 33 376 161.3 173.6 60.6 65.2 99.7 0.2 1:6.3 

M3 20/02/03 25/03/03 33 376 246.2 224.1 92.6 84.3 97.4 -0.3 - 

M4 * 20/02/03 25/03/03 33 137 390.6 408.4 53.4 55.6 ¥ 98.8 ¥ 0.1 ¥ - 






(FCR) for silver perch (Bidyanus bidyanus) from the 08/04/03 up to 08/04/04 in 12, 17.5 and 

23m 3 raceways. Where FCR values are not provided their calculation had been invalidated by a 

lack of growth, a reduction in biomass through stock loss, or a reduction in biomass from fish 

harvest 


(g) (g) (kg/m 3 ) (kg/m 3 ) 

S1 22/04/03 29/12/03 251 3525 3.9 19.2 13.6 67.5 99.7 1.6 1:0.9 

S2 22/04/03 29/09/03 160 1305 7.2 14.5 9.36 19.0 99.6 0.9 1:2.0 

S4 13/05/03 29/12/03 230 817 18.2 31.3 14.8 17.5 68.3 0.3 1:28.8 

S5 13/05/03 08/01/04 240 473 36.2 71 17.1 32.4 94.5 0.4 1:4.6 

S6 08/04/03 08/01/04 275 1355 68.0 92.9 92.5 127.5 92.7 0.2 1:2.2 

M1 13/05/03 29/12/03 265 807 61.7 97.1 49.8 69.7 88.9 0.1 1:5.5 

M2 13/05/03 08/01/04 195 414 121.6 166.6 50.3 67.1 97.4 0.2 1:3.2 

M3 13/05/03 08/01/04 265 407 128.4 173.3 52.2 44.8 63.6 0.1 - 

M4 13/05/03 08/01/04 265 270 183.2 257.5 49.4 53.8 77.3 0.2 1:23.6 

M5 13/05/03 08/01/04 275 263 253.8 225.9 68.3 43.9 73.9 0.0 - 

L1 * 13/05/03 08/01/04 80 137 357.1 314.1 48 17.7 ¥ 35.9 ¥ 0.0 - 




In general, the growth of fish in raceways during this study was generally slower than that required for 

successful commercial culture. This was in part due to the poor water quality conditions present for the 

majority of the study period as the result of periodic riverine harvesting activities. The best growth 

rates for silver perch were generally obtained in summer months early in the study when water quality 

was at its best. 

37

The average rate of growth for silver perch was highest in net cages following their initial stocking in 

late 2000. During this period the average rate of growth of all animals below 50 g was 3.5 per cent per 

day while the rate of growth for animals above 50 g averaged 1.3 per cent per day. Animals stocked at 

an average size of 58 g reached 137 g after 10 weeks. During the same period fish stocked at an 

average weight of 9.4 g and 5.9 g reached 50 g and 35 g respectively after 10 weeks. However, these 

favourable rates of growth slowed after a major pumping event in February when water turbidity 

increased and dissolved oxygen levels decreased. Low DO levels stress fish, reduce feeding activity 

and lower feed conversion efficiencies (Diana, 1997). However, despite the comparative fall in growth 

rates after the February pumping event the average growth of caged fish was still generally better that 

that observed in the floating raceways during the same period in later years. 

The major issues associated with the use of net cages were the retention of fish and the generally poor 

FCR values. Although growth in cages was favourable the amount of feed used was high because of 

difficulties in feed delivery, feeding behaviour and also stock retention. Stock retention in net cages 

was as low as 36.4 per cent in cages that actually reached harvest. The loss of fish from cages during 

this study was approximately 25,000. Most were lost from cages holding small fish (

density of 94 kg/m 3 . Similarly, catfish grown at densities of 63.4 kg/m 3 have been reported as being 

achieved with FCR’s between 1.8 and 2.1 feed to satiation, and an average survival of 83.6 per cent 

(Yoo et al, 1995). The higher densities have been reported for catfish at 136-154 kg/m 3 (Masser, 

Wilcox, Yoo and Sonnenholsner, 1999). Additional studies conducted by the authors (Appendix 1) 

demonstrated the same raceway system as used in this study could be used to successfully growout 

barramundi (Lates calcarifer) while achieving significant operational cost savings with respect to feed 

use, labour and stock retention. In the case of barramundi, fish stocked in 14 m 3 raceways at 28.5 g 

were grown to 128.5 g in 75 days with a survival rate of 94.2 per cent and an FCR of 1.17. When 

compared to the farms cage culture results, the FCR, survival and labour costs in raceways were 65, 

15, and 59 per cent lower in raceways (Authors unpublished data). Similarly, although not achieved in 

this study, the culture of Murray cod in raceways is showing promise. A recent harvest of cod from a 

floating raceway operation established on a farm reservoir in southern Queensland recently began 

harvest of 1 to 2 kg Murray cod in its second year of operation (Matteo Barchesi, pers comm). Another 

farm has been established for freshwater eels (Anguilla reinhardtii) using the same technology as Loch 

Eaton on an irrigation storage in coastal south east Queensland. This system is also performing well 

with eels over 1 kg being produced at densities of 87 kg/m 3 and above (Samuel Bell, pers comm). 

In this study, the performance of silver perch in floating raceways was detrimentally affected by the 

prevailing water quality conditions at Loch Eaton. The performance of this species under more 

favourable conditions should be investigated. However, species such as Murray cod may be better 

suited to the floating raceway system because of their proven performance at culture densities in 

excess of 80-150 kg/m³ (VDPI). While the cage trials for Murray cod attempted in this study were 

encouraging, stock losses due to escape prevented the collection of data beyond the juvenile stage. 

Future establishment of aquaculture facilities in cotton catchments within the Murray Darling basin 

should consider the Murray cod as the prime species of investigation if intensive systems like the 

floating raceway technology are to be used. 

Although the raceways did generally maintain high densities of fish during periods when DO levels 

were chronically low, significant stock mortalities were observed on at least one occasion when 

oxygen levels fell rapidly in response to a large riverine pumping event. Additional oxygen 

supplementation capacity has been installed in other floating raceway systems for emergency 

applications and is likely to have alleviated the acute oxygen debt experienced during the harvest of 

flood waters in this study. Alternatively, more appropriate placement of the aquaculture operation 

would serve to buffer the system from the introduction of large volumes of poorly oxygenated water. 

At Loch Eaton this would involve relocating the aquaculture operation from the ring tank that receives 

water during events to the adjacent ring tank cell which is filled via overflow from the receiving ring 

tank (Fig 4.4.1). This would enable some settlement and oxygenation of water within the receiving 

ring tank while decreasing the total water exchange through the aquaculture storage. In addition, when 

water levels are low farms like Loch Eaton could pass groundwater through the aquaculture ring tank 

in order to further improve water quality. However, the use of groundwater in this way would only be 

recommended if it occurred in conjunction with irrigation events so as to reduce water losses. The 

storage of groundwater in above ground ring tanks for extended periods will result in significant losses 

due to seepage and evaporation. In some cases the additional pumping costs and infrastructure 

required to deliver groundwater to the aquaculture ring tank may be prohibitive. In these situations the 

correct placement of the aquaculture operation in ring tanks receiving surface waters becomes critical 

as does a consistent and reliable surface water flow. 

39

R 

E 

Figure 4.4.1 Existing (E) and recommended (R) locations of aquaculture facilities and pumping 

infrastructure at Loch Eaton. Relocation of the floating raceway facility from the primary ring 

tank to the adjacent storage would serve to buffer the aquaculture facility from acute falls in 

dissolved oxygen as the result of harvesting large volumes of oxygen deficient, highly turbid 

flood waters 

Although over the course of the study it was observed that the raceways were more secure against bird 

strike and frequency of stock escape, the higher numbers of fingerlings held in each raceway meant 

that just two events represented a larger loss of stock than were experienced with cages. Over 60,000 

fingerlings were lost in two separate events. The first was related to operator error where a large 

meshed screen was used for small fingerlings at stocking resulting in the escape of an estimated 

50,000 fish. The second was related to a damaged rear screen which permitted the escape of over 

10,000 fingerlings. The cause of this event was unknown but prompted a review of the securing of the 

plastic oyster mesh screen to the raceways. Both events do highlight the higher risk associated with 

running high densities of fish in raceways located in open water bodies. 

While the growth of silver perch in this study was generally lower than that required for a successful 

commercial operation it did highlight the benefits and constraints of the two systems most likely to be 

applied. In this instance net cages returned favourable rates of growth but proved problematic with 

respect to stock retention, food conversion, disease management and labour requirements. Their use 

also restricted the farms irrigation capacity with respect to the volume of water required to enable their 

operation. The drop of the larger net cages required the ring tank water level to maintained essentially 

at capacity or al least 6 m to allow 1m clearance from the bottom of the storage. In contrast the 

floating raceways remained operational even when water levels had fallen to less than 2 m. In terms of 

the impact of the aquaculture on the whole of farm operation the ability to utilise more of the ring tank 

water for irrigation is a significant advantage for the raceway system over cage culture. In addition, the 

advantages observed in this and other studies concerning the productivity of raceways means that food 

conversion, labour costs and stock losses can all be reduced through the use of floating raceways 

instead of net cages. 

When proposing to develop aquaculture in cotton storages it is recommended that the ability to 

maintain water quality be considered with respect to the placement and operation of the aquaculture 

40

facility. Regardless of the type of production systems being employed the success of the aquaculture 

operation will depend upon appropriate planning and management of the farms integration to avoid 

issues of poor water quality, lack of water, overstocking, poor growth or survival. 

41

5. Pesticide Monitoring and Residues 


The presence of large well serviced water infrastructure on irrigated farms makes integrated 

aquaculture a potentially significant diversification activity. However, the development of the cotton, 

grains and sugarcane industries has relied on the use of a variety of pesticides, herbicides and 

defoliants applied either aerially, by ground spray rigs or directly to the soils themselves. A recent 

study by Muller et al, 2000, demonstrated that pesticide contamination was widespread in irrigation 

areas in Queensland. Many agricultural chemicals will accumulate rapidly through the food chain, 

especially in aquatic environments. 

Farms that use, or have used these chemicals in the past are at risk of producing product contaminated 

through at levels that pose food safety and market access issues. Unlike many other food products, the 

maximum residue limit (MRL) for many environmentally persistent compounds, have not been set for 

fish. The MRL is the maximum permissible residue limit for agricultural or veterinary chemicals that 

are listed for use on a particular product. For products where the MRL has not been set an extraneous 

residue limit (ERL) applies. The ERLs are for compounds that originate from environmental sources 

of contamination rather than from application of these agents directly or indirectly to the crop. The 

ERL for pesticides in fish are set at the reliable limit of quantification (Table 5.1.1.). 

Table 5.1.1 Extraneous Residue Limits (ERL) for agricultural chemicals in whole fish (minus 

gut) according to Food Standards Australia New Zealand, Australia New Zealand Food 

Standards Code (FSANZ, 2006) 

Chemical ERL (mg/kg) 

Aldrin & Dieldrin 0.1 

BHC 0.1 

Chlordane 0.05 

DDT 1 

HCB 0.1 

Heptachlor 0.05 

Lindane 1 

Fish are highly susceptible to the effects of pesticide contamination (Table 5.2.1). The 96 hr LC50 for 

endosulpfan exposure for native fish has been reported to lie between 0.2 μg/l for bony bream 

(Nematolsa erebi) to 2.4 μg/l silver perch (Bidyanus bidyanus) (Sunderam et al, 1992). During storm 

events endosulfan levels as high as 1.3 μg/l have been recorded in cotton growing regions (Muschal 

and Cooper, 1998). In addition to the sometimes lethal consequences of pesticide contamination, sublethal 

exposures result in the rapid bio-accumulation and concentration of those chemicals and their 

breakdown products. Bio-concentration occurs when fish absorb the compound directly from the water 

only while bio-accumulation refers to the build up of residues through the food chain (trophic transfer) 

and from the water (Macek et.al., 1979). Bio-magnification occurs when the level of residue increases 

through the food chain within two-trophic levels (Macek et.al., 1979). 

Different species of fish have been observed to have different patterns of residue build-up as a result of 

their feeding behaviour (trophic level). In the case of many now banned but persistant organochlorine 

(OC) compounds (aldrin, DDT, lindane, heptachlor etc), residues build up to levels often many 

thousand times higher than those observed in sediments and other biota. They can remain in the 

animal’s fat deposits for many years, if not its life. The build up of such residues can pose significant 

dangers to other wildlife (particularly birds) and also humans (most notably pregnant women). On the 

other hand, other less persistent compounds such as the organophosphate (OPs) and synthetic 

pyrethroids (SPs) do not generally bio-concentrate or accumulate, but if they do, they can be readily 

42

oken down and their metabolites and rapidly cleared. The rate of this clearance is dependent on 

temperature, feeding behaviour and solubility of the contaminating chemical (fat or water soluble). 

The potential risk of contaminated aquaculture product reaching the market must be understood and 

managed for the development of aquaculture in cotton catchments to proceed. While the exposure of 

native fish to environmental contaminants such as agricultural chemicals has been documented 

(Hunter, 1992 and Connell, Miller and Anderson, 2002), the study of bio-concentration and rate of 

depuration of OCs, OPs and SP compounds in farmed Australian native fish has not been reported. 

The objective of this study was to collect and analyse the edible portion of farm raised silver perch 

(B. bidyanus) to determine if residues from pesticides used on farm could be detected. The primary 

agents of concern were endosulfan and chlorpyrifos. Endosulfan is the only OC insecticide still 

permitted for use on crops in Australia. It has a reported half life of 50 days in soil and can be 

metabolised to form endosulfan sulphate, diol, ether, hydroxyether and lactone assuming exposure is 

below lethal levels (EXTOXNETa and IPCS INCHEM). In fish the lethal concentration can be as low 

as 1.2 ug/L (EXTOXNETa). 

Other OC compounds that were previously used in agriculture before being banned include DDT, 

dieldrin, endrin, chlordane, heptachlor and aldrin. These agents have relatively long half lives, are 

stable in soils and are relatively stable in sunlight. DDT was the most widely used OC which, while 

economical, was banned because of its long half life in the environment and the detrimental effect is 

accumulation had on wildlife and potentially human health (Ware, 1986). Chlorpyrifos is an OP which 

is still widely used in agriculture. The use of chlorpyrifos in the Australian cotton industry is 

decreasing. The use of chlorpyrifos has been reduced through the better management of pests through 

integrated pest management practices and the use of genetically selected, pest resistant cotton strains 

such as Ingard and Bolgard. The sensitivity and effect of fish species to chlorpyrifos varies with 

different tolerances displayed by different species (Racke, 1993). 

Bioaccumulation studies have been performed in a number of fish species but none with silver perch. 

No information exists in regard to the actual rate of elimination from Australian native fish species for 

the agents to be studied. There is no information on the rate of elimination of breakdown products 

such as DDE (dichlanodiphenyl dichloroethylene) in native fish and no information on the elimination 

of βHCH (Beta hexachlorocyclohexane) in any fish species (USEPA, 2000). The only alternative to 

these studies is to use estimates of accumulation rates in non-native fish species, tested under different 

environmental conditions and protocols. While this information is valuable in providing some 

background for developing a model of pesticide bioaccumulation, it cannot be relied upon to 

determine the actual risk or absolute rate of bio-concentration of these products under culture 

conditions. In addition the rate of elimination and the effectiveness of purging practices may also be 

also highly dependent on culture conditions and diligence of the operator. 

The results of this study will however further the understanding of the risks associated with integrating 

aquaculture with cotton farming activities in Australia. 


5.2.1 Pesticide Monitoring 

To assess the effectiveness of management practices introduced to prevent contamination of cultured 

fish, in situ monitoring of the aquaculture ring tank and its water supply were conducted. As part of 

this monitoring extensively (free range) and intensively (cage/pond) raised silver perch were assessed 

for pesticide residues on a monthly basis for a two year period. In addition, in vivo studies of pesticide 

uptake and clearance in farmed fish were conducted. The rate of pesticide elimination and the role of 

purging on clearance rates were investigated using silver perch. The agents used in these trials were 

selected on the basis of their environmental persistence. 

43

5.2.1.1 Pesticide Application and Use 

The list of chemical used on farm during the monitoring period and their active constituents are 

presented in Table 5.2.1. The monitoring period commenced in February 2001 and was completed in 

May 2003. The list of compounds tested for is provided in Table 5.2.2 and 5.2.3. Although many of 

these compounds are not presently used on cotton they may be persistent in the environment as a result 

of previous use or be present in water from the catchment and supplied to the ring tank during 

pumping. 

Table 5.2.1 List of agri-chemicals used at Loch Eaton from February 2001 to May 2003 

Agent 

Toxicity to fish 

Bio-accumulates / bioconcentrates 

in fish 

Reference 

amitraz Medium - High No PAN, 2006 

bifenthrin Very Highly No PAN, 2006 

chlorfenapyr Very Highly Yes (low) ACC, 1997 

chlorpyrifos High Yes PAN, 2006 

β-cyfluthrin Very Highly No PMEP, 2006 

cypermethrin Medium - High Yes PAN, 2006 

deltamethrin Medium - High Yes PAN, 2006 

diuron Low - Medium Yes PAN, 2006 

ethephon Not Acutely Toxic No PAN, 2006 

ethion Medium - High No PAN, 2006 

indoxacarb (25:75) Medium - High No USEPA, 2006 

mepiquat present as mepiquat chloride Not Acutely Toxic No PAN, 2006 

thidiazuron Slightly Toxic No PAN, 2006 

Table 5.2.2 List of organochlorine, organophosphate and pyrethroid compounds included in 

analytical testing of riverine and ring tank water samples 

Organochlorine Organophosphate Synthetic pyrethroid 

Aldrin Azinphos Ethyl Ametryne 

alpha-BHC Azinphos Methyl Atrazine 

alpha-Endosulfan Carbaryl Atrazine Desethyl 

beta-BHC Diazinon Atrazine Desisopropyl 

beta-Endosulfan Dichlorvos Pendimethalin 

Chlorpyrifos Dimethoate Prometryne 

Chlordane EPTC Propazine 

delta-BHC Fenamiphos Simazine 

Dieldrin 

Fenitrothion 

Endosulfan Sulphate 

Fenthion 

Endrin 

Malathion 

Heptachlor 

Methidathion 

Heptachlor epoxide 

Methyl Parathion 

Hexachlorobenzene (HCB) 

Omethoate 

Lindane (gamma-BHC) 

Parathion 

Methoxychlor 

Profenofos 

Metolaclor 

DDD 

DDE 

DDT 

Tri-allate 

Trifluralin 

44

Table 5.2.3 List of organochlorine, organophosphate and synthetic pyrethroid compounds 

included in analytical testing of fish samples 

Organochlorine Organophosphate Triazine & other 

Aldrin Bromophos ethyl alpha Cypermethrin 

alpha-BHC Carbophenothion beta-cyfluthrin 

alpha-Endosulfan Chlorfenvinphos Bifenthrin 

beta-BHC Chlorpyrifos Cyfluthrin 

beta-endosulfan Chlorpyrifos-ethyl Cyhalothrin 

Chlordane Chlorpyrifos-methyl Cypermethrin 

DDD Coumaphos Deltamethrin 

DDE Diazinon Fenvalerate 

DDT 

Dichlorvos 

Dieldrin 

Dimethoate 

Endosulfan sulphate 

Ethion 

Endrin 

Fenitrothion 

HCB 

Fenthion 

Heptachlor 

Frenchlorphos 

Heptachlor epoxide 

Malathion 

Lindane 

Methidathion 

Methoxychlor 

Oxychlordane 

Parathion 

Parathion-methyl 

Pirimiphos-methyl 

Profenofos 

5.2.1.2 Water 

Monthly water samples were collected from the ring tank and the adjacent river. These samples are 

collected and stored in acid washed 1 L glass Schott bottles fitted with a teflon lid. The samples were 

either forwarded immediately for analysis or frozen at -20°C to ensure volatilisation of sensitive 

compounds did not occur. In the event that pesticides were applied to adjacent crops by aerial 

application, a sample from both the river and the ring tank was obtained prior to application, 

immediately following application, and for several successive days in order to assess the risk 

associated with pesticide spray drift. All water samples were analysed by the Department of Primary 

Industries and Fisheries (DPI&F) Leslie Research Centre, Toowoomba or by Australian Government 

Analytical Laboratories (AGAL), Cannon Hill. The list of compounds tested for is provided in 

Table 5.2.2. 

5.2.1.3 Fish 

Monthly fish samples were collected in order to monitor the pesticide uptake by the aquaculture stock. 

A sample of six fish per month was collected from the largest and oldest available size class, and when 

available, free-range fish caught from the ring tank were also collected. All fish samples were frozen 

whole at -20°C until analysis. All fish samples were analysed as whole carcass, minus gut, and as 

edible portion (fillet) as per the analysis criteria established by the National Residue Survey (NRS) 

(DAFF, 2001). The list of compounds tested for is provided in Table 5.2.3. 

5.3 Pesticide Bio-concentration and Depuration 

5.3.1 Agents 

The OCs and OPs used in the trial were heptachlor, dieldrin, endosulphan sulphate, chlorpyrifos, p,p- 

DDE, o,p-DDE, metolachlor, lindane and β-BHC. Standards were obtained from the (DPI&F), Leslie 

Research Centre Toowoomba. All fish were exposed to a 1μg/L concentration of each of the agents. 

All standards were at least 97 per cent pure. A working solution was made-up to service the trial by 

dissolving agents in acetone to form a stock solution. The working solution was then added to each 

tank to create 1 μg/L concentration of each pesticide. 

5.3.2 Fish 

A total of 216 purged fish with an average weight of 450 g were purchased from Arthur Raptis and 

Sons (fish wholesalers), Brisbane. Fish were first held in two separate acclimation tanks for four days 

45

prior to the commencement of the trial as temperature was increased from the ambient temperature of 

22ºC to 25ºC and from ambient to 15ºC. No feed was provided throughout the trial. Three fish were 

exposed to agents for 24 hrs before the commencement of the trial to monitor survival and ensure 

exposure levels were not toxic. 

5.3.3 Treatments 

The first treatment was maintained at 25ºC to imitate summer conditions and the second treatment was 

held at 15ºC to imitate winter temperatures. An exposure time of 96 hours was used during the bioconcentration 

period and a dose of 1μg/L for both temperature treatments. The pesticide bioconcentration 

and depuration trial using silver perch, Bidyanus bidyanus, exposed each treatment to a 

1 μg/l dose of either heptachlor, dieldrin, endosulphan sulphate, chlorpyrifos, p,p-DDE, o,p-DDE, 

metolachlor, lindane and βBHC at 15 and 25ºC for a period of 96 hrs. This was followed by a 

depuration period of up to 28 days. 

5.3.4 Sampling and Analysis 

A control sample consisting of three fish was taken at time zero and analysed to ensure that no residue 

was pre-existing in fish before trial commencement. To monitor pesticide uptake, three fish were 

removed from each replicate at 12, 24, 48, 72, and 96-hour intervals from both treatments. To monitor 

pesticide clearance, fish were held for 28 days while samples were collected at time intervals of 1, 3, 5, 

7, 14, 28 days. Samples collected were pooled and comprised of three fish from each individual 

replicate. All fish sampled were humanely euthanased and immediately frozen. Analysis of sample 

fish was conducted by AGAL. Samples were supplied at regular intervals in batches of three whole 

fish/bag. The gut was removed by AGAL and the three fish were homogenised into one and tested for 

the nine individual pesticides. Results were returned in units of mg/kg for each pesticide. 

5.3.5 System and Husbandry 

Trials were conducted in triplicate with three 700 L tanks containing 24 fish each utilised for each 

treatment. Adsorption of the pesticide to foreign sources within tanks was minimised by using solid 

fibreglass tanks fitted with ceramic air stones. A 100 per cent water exchange was conducted daily 

with the stock solution re-added at the concentration required using the stock solution. The 

concentration of each agent in was analysed. 

All fish were exposed to the same conditions and culture environment. Under these conditions, the fish 

showed no clinical signs of injury or stress during the exposure period. Prior to commencement of 

depuration period, all tanks used during the bio-concentration period were removed, thoroughly 

washed and rinsed with acetone twice. The floor of the study area was washed down and scrubbed 

with powdered activated carbon. All equipment was washed or replaced including new air stones, nets 

and sampling equipment. 

Due to a suspected parasitic infection, some mortality occurred on day eight and day nine of the 

depuration period in 15ºC treatment. The salinity of all tanks was increased from 0ppt to 10 ppt in 

order to treat the infestation. This had a positive effect on fish behaviour and no more mortality was 

observed throughout the remainder of the trial. 

All wastewater from the trial was pumped to an outside tank and exposed to direct sunlight. This water 

was treated for 24 hrs with powdered activated carbon (PAC) at a rate of 100 mg/L. The water was 

then drained, the PAC collected in a fine mesh sieve and dispatched for commercial incineration. 

46

5.4 Results 

5.4.1 Pesticide Monitoring 

5.4.1.1 Water 

The most likely pathway for the contamination of cultured fish is via the water column. A total of 29 

fish samples were collected from February 2001 to May 2003. No OC or pyrethroid compounds were 

detected in the flesh of silver perch farmed in net cages or in raceways. Similarly these compounds 

were not detected in free ranging fish from the ring tank. According to records, no DDT or other now 

banned OC’s have ever been used on this farm. Since pyrethroids do not bio-accumulate in fish, it was 

expected that these compounds would remain below the limit of quantification. 

A total of 61 water samples from the ring tank and 15 from the adjacent river were collected and 

analysed. The compounds that were detected in order of decreasing occurrence in ring tank samples 

were atrazine, metolachlor , atrazine desethyl, prometryne, chlorpyrifos and atrazine desisopropyl 

(Table 5.4.1). By comparison, the compounds detected in river samples were (in order of decreasing 

occurrence) atrazine, metolachlor, simazine, prometryne, and atrazine desethyl (Table 5.4.2). The 

timing of these detections is illustrated in Figures 5.4.1 and 5.4.2. 

Chlorpyrifos was detected in ring tank water on the 02/02/02 at a level of 0.53μg/L. The concentration 

of this agent decreased over subsequent sampling events and was below the limit of detection 12 days 

later on the 14/02/02. Chlorpyrifos was not detected in river water samples collected at the same time. 

The detection of chlorpyrifos in ring tank water did not correspond with Loch Eaton’s spraying 

activities. A review of farm records and those of their neighbours indicates a spray event on an 

adjacent property was the likely source of chlorpyrifos contamination. No similar events were 

subsequently detected. 

Table 5.4.1 Ranges of agents detected in Ring tank water 

Detected Agent 

Range (µg/L) 

Atrazine 0.10 to 6.06 

Atrazine desethyl 0.12 to 0.70 

Chlorpyrifos 0.01 to 0.53 

Metolachlor 0.030 to 1.49 

Prometryne 0.02 to 0.30 

Atrazine desisopropyl 0.1 to 0.1 

Table 5.4.2 Ranges of agents detected in River water 

Detected Agent 

Range (µg/L) 

Atrazine 0.05 to 16.92 

Metolachlor 0.03 to 3.39 

Simazine 0.17 to 0.30 

Prometryne 0.03 to 0.38 

Atrazine desethyl 0.06 to 0.96 

5.4.1.2 Fish 

A single detection of chlorpyrifos was recorded in fish collected during the 2001-02 cotton season. 

Chlorpyrifos in free range and caged silver perch were 0.072 and 0.210 mg/kg respectively on the 

04/02/02. The level of chorpyrifos in ring tank water at this time was 0.53 μg/L. No mortalities were 

recorded in cultured or extensively stocked fish that were associated with the chlorpyrifos event. All 

subsequent fish samples had no detectable level of chlorpyrifos residue (free range, caged or raceway 

fish). 

47

5.4.2 Pesticide Bio-concentration and Depuration 

Uptake and clearance trials for OC and OP compounds in farmed silver perch demonstrated that 

standard purging practices can be used to clear OP compounds such as chlorpyrifos but not 

environmentally persistent OC compounds such as p,p-DDE, o,p-DDE, βBHC, lindane, heptachlor 

and dieldrin (Figs 5.4.3 and 5.4.4). 

The uptake of DDE was rapid at 25ºC climbing from 0.08mg/kg at 48hrs to 0.36mg/kg on third day of 

purging (Fig 5.4.4). The concentration of heptachlor also peaked after 3 days at 0.12mg/kg in the 25ºC 

treatment while βBHC, lindane and dieldrin levels reached their respective peaks of 0.15, 0.15 and 

0.27 mg/kg at the 96hrs exposure mark. In a similar pattern, DDE and heptachlor concentrations in the 

15ºC treatment were highest during the purging period reaching 0.28 and 0.12 mg/kg respectively 

(Fig 5.4.3). The concentrations of βBHC, lindane and dieldrin all peaked at a concentration of 

0.12mg/kg. 

The concentration of chlorpyrifos in the 25ºC treatment peaked at 0.09 mg/kg at 96 hrs exposure and 

fell to below the Limit of Quantitation (LOQ) by the 14th day of the elimination period. Chlorpyrifos 

levels in the 15ºC treatment reached the equivalent of their peak concentration of 0.08 mg/kg after 

96 hrs of exposure. The time taken to reach levels below the LOQ was 28 days in the 15ºC treatment. 

0.8 

7 

0.7 

6 

Other Pesticides (ug/L) 

0.6 

0.5 

0.4 

0.3 

0.2 

5 

4 

3 

2 

Atrazine & Metalochlor (ug/L) 

0.1 

1 

0 

0 

1/02/03 

1/01/03 

1/12/02 

1/11/02 

1/10/02 

1/09/02 

1/08/02 

1/07/02 

1/06/02 

1/05/02 

1/04/02 

1/03/02 

1/02/02 

1/01/02 

1/12/01 

1/11/01 

Chlorpyrifos Atrazine Desethyl Atrazine Desisopropyl Prometryne Metalochlor Atrazine 

Figure 5.4.1 Pesticide levels in ring tank water from November 2001 until March 2003 

48

Other Pesticides (ug/L) 

3.5 

3.25 

3 

2.75 

2.5 

2.25 

2 

1.75 

1.5 

1.25 

1 

0.75 

0.5 

0.25 

0 

17 

16 

15 

14 

13 

12 

11 

10 

9 

8 

7 

6 

5 

4 

3 

2 

1 

0 

Atrazine & Metalochlor (ug/L) 

1/02/03 

1/01/03 

1/12/02 

1/11/02 

1/10/02 

1/09/02 

1/08/02 

1/07/02 

1/06/02 

1/05/02 

1/04/02 

1/03/02 

1/02/02 

1/01/02 

1/12/01 

1/11/01 

Metalochlor Atrazine Desethyl Atrazine Desisopropyl Prometryne Simazine Atrazine 

Figure 5.4.2 Pesticide levels in river water from November 2001 until March 2003 

0.3 

0.25 

0.2 

ug/L 

0.15 

0.1 

0.05 

0 

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 

Days 

Metolachlor Chlorpyriphos DDE Dieldrin 

beta BHC gamma BHC (Lindane) Heptachlor Endosulfan sulphate 

Figure 5.4.3 Concentration of pesticides in muscle tissue of silver perch (Bidyanus bidyanus) 

maintained at 15ºC and exposed to 1 μg/L heptachlor, dieldrin, endosulfan sulphate, 

chlorpyrifos, p,p-DDE, o,p-DDE, metolachlor, lindane and β-BHC for 96hrs then transferred to 

clean water for a period of up to 28 days 

49

0.4 

0.35 

0.3 

0.25 

ug/L 

0.2 

0.15 

0.1 

0.05 

0 

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 

Days 

Metolachlor Chlorpyriphos DDE Dieldrin 

beta BHC gamma BHC (Lindane) Heptachlor Endosulfan sulphate 

Figure 5.4.4 Concentration of pesticides in muscle tissue of silver perch (Bidyanus bidyanus) 

maintained at 25ºC and exposed to 1 μg/L heptachlor, dieldrin, endosulfan sulphate, 

chlorpyrifos, p,p-DDE, o,p-DDE, metolachlor, lindane and β-BHC for 96hrs then transferred to 

clean water for a period of up to 28 days 

Concentrations of metolachlor and endosulfan sulphate were below the FSANZ ERL’s of 0.05 mg/kg 

(FSANZ, 2006). Studies on fish exposed to metolachlor indicate that very little is accumulated and 

that any accumulated material is excreted rapidly when fish are placed in clean water (USEPA, 1997). 

Endosulfan bio-accumulates in fish but will be eliminated over time if the animal is placed in noncontaminated 

waters. The failure to detect endosulfan in any form in this study indicates that the 

concentration used in this study were insufficient to result in bio-concentration of endosulfan to 

detectable levels in muscle tissues. Samples of the water from treatment tanks returned endosulfan 

levels of 1.4 and 1.1μg/L after 4 and 18 hrs after inoculation. Similarly, metolachlor levels were 1.2 

and 0.93 μg/L after 4 and 18 hrs post inoculation. 


Of the seven compounds that were found to be present in ring tank water (Metolachlor , simazine, 

atrazine, atrazine desethyl, atrazine desisopropyl, prometryne and simazine) only chlorpyrifos was 

applied on farm during the monitoring period. The detection of chlorpyrifos did not correspond with 

any spray event as a result of spraying activity conducted on Loch Eaton. It is likely that the single 

detection of chlopyrifos was associated with an activity conducted on a neighbouring property. Spray 

drifts can result from rapid shifts in wind direction and/or a surface temperature inversion. An 

inversion or change in wind direction could potentially permit drift of pesticides for up to 500 m from 

its point of application (Craig, Woods and Dorr, 1998). The other compounds observed in this study, 

primarily pyrethroid compounds, are most likely to have been introduced during water harvesting 

events from the adjacent Condamine River. 

Atrazine and its breakdown products atrazine desethyl and atrazine desisopropyl were detected in 

67 per cent and 95 per cent of the water samples from the river and the ring tank. Atrazine is a pre and 

post-emergent herbicide that is widely used for the control of some annual grasses and broadleaf 

weeds. It is not used in irrigated agriculture and is present as the result of run-off from other more 

diffuse land uses (Muschal and Cooper, 1998). Since water is pumped directly from the river at Loch 

Eaton, atrazine is introduced into the ring tank during these pumping events that often accompany 

50

flood events. The high levels of atrazine in river water samples compared to ring tank samples, 

demonstrates this pattern of movement. 

Atrazine degrades more rapidly under anaerobic compared to aerobic soil conditions (Goswami and 

Green 1971). In the aqueous phase, the products of atrazine biotransformation are reported to peak 

after 25 days and then decline (Seybold et.al., 2001). The concentrations of these products, atrazine 

desethyl and atrazine desisopropyl, peaked after the pumping events as did the atrazine levels 

themselves. Atrazine levels declined between events and it is likely that this decline contributed to 

ongoing detection of atrazine desethyl and atrazine desisopropyl. These products bind strongly with 

soil (Seybold and Mersie 1996) and it is likely that this binding with soil, rather than any continued 

breakdown, accounts for a large proportion of the observed decreases in these metabolites over time. 

While atrazine does not bio-accumulate in fish it can have physiological consequences including 

effects on haematocrit, other serum components, the liver, osmoregulation and respiration (Prasad 

et.al., 1991; Egaas et.al., 1993; Hussein et.al., 1996). Fish exposed to 3 and 6 mg/L of atrazine display 

clinical signs of stress including increased respiration rates, slow down of reflexes, erratic swimming 

and reduced feed intake (Hussein et. a., 1996). The atrazine LC50 value for fish has been reported to be 

between 3 and 18.8 mg/L and varies according to species and environmental conditions (Pluta 1989; 

Neskovic et al, 1993; Hussein et.al., 1996). In this study, the highest concentration of atrazine 

observed in ring tank water was 6.06 μg/L. This is lower than levels reported to cause mortality in fish 

but levels as low as 10 μg/L have been reported as causing amplitude changes (increases in respiration 

which is a sign of stress) and fatty liver degeneration in rainbow trout (Barnhart, 1969; Huessein et.al., 

1996). No information exists concerning the sensitivity of silver perch and other native fish such as 

Murray cod to atrazine. This study did not have capacity to identify if atrazine levels in ring tank water 

had any deleterious effect on fish behaviour or growth. It is recommended that further studies be 

conducted using native fish to determine if sub-lethal exposures, such as those observed in this study, 

result in any clinical signs of stress or physiological degeneration that can impact fish behaviour 

and/or growth. 

Metolaclor was also detected in ring tank samples after pumping events but at lower levels than were 

observed in the river. Under aerobic conditions in the laboratory the half life of metalochlor is 

210 days. In anerobic wetland soils the half life for metolachlor is reported to be 62 days (Seybold and 

Mersie 1996). This compares to 38 days for atrazine under the same conditions. Metalochlor levels in 

the ring tank fell between pumping events and was not detected after August 2002. The bioconcentration 

of metalochlor in fish is considered not to be important as the compound is rapidly 

depurated by fish held in clean water (USEPA, 1997). No metalochlor was detected in fish samples 

collected at the same time as the detection of this agent in ring tank water. Prometryne was also not 

detected in any fish samples collected from the ring tank but it was detected in 48 per cent of ring tank 

and 27 per cent riverine water samples during the monitoring period. 

Simazine was detected in ring tank water but not in riverine samples at that time. Simazine does not 

bio-accumulate in fish (Kidd and James, 1991). The LC50 dose for simazine for rainbow trout is 

reported as being 100 mg/L which is about 6,000 times higher than the levels observed in this study 

(EXTOXNETb). Simazine is used to control many broadleaf weeds and annual grassess and like 

atrazine can remain in the aquatic environment for an extended period. The levels and incidence of 

simazine detection would not appear to pose any threat to aquaculture. Other SP compounds that were 

used on-farm but not tested for during the monitoring activities include cypermethrin and indoxacarb. 

Cypermethrin is highly toxic to fish, has a half life in soil of 30 days, but is extremely lipophilic and is 

immobile in soils and is rapidly metabolised by animals (NPTN, 1998; EXTOXNETc). The LC50 for 

cypermethrin is cypermethrin in rainbow trout is 0.0082 mg/L (EXTOXNETc). Indoxacarb is 

considered moderately to highly toxic to fish on an acute basis with LC50 values of between 24 and 

1300 μg/L. Indoxacarb, it’s isomers and associated degradates are moderately to very highly toxic to 

freshwater and marine fish on an acute basis with LC50s ranging from 0.024 to >1.3 mg/L (Moncada, 

2003). 

51

There were no detections of endosulfan in water samples from the river, ring tank or fish collected 

during this monitoring exercise. Endosulfan has not been found to bio-accumulate in fish populations 

between cotton growing seasons but any detection in aquaculture product (>0.05mg/kg) would be a 

violation of the FSANZ guidelines. Studies show that pond LC50 values for silver perch (3.2 and 

4.4 μg/L (Patra et.al., 1995a; Patra et.al., 1995b) are similar to laboratory LC50 values of 2.4 μg/L 

(Sunderam et.al., 1992). The lack of detection of endosulfan in this study is encouraging and is 

indicative of a reduction in the use of this chemical and others by the cotton industry in recent years. 

Endosulfan use peaked on an industry level in the 1998/99 season but in the 2003/04 season its use 

had fallen by significantly (Bruce Pyke, pers. Comm..). The decline in the concentration of endosulfan 

in cotton gin trash collected from the 1998/99 and 2003/04 seasons, illustrate the dramatic reduction in 

endosulfan use on farms growing Bolgard cotton. No endosulfan sprays were used on Loch Eaton 

during this monitoring period. Other factors that account for the reduction in pesticide use in the 

cotton industry include the widespread adoption and success of the industries Best Management 

Practices (BMPs) and Integrated Pest Management (IPM) practices. The reduction in endosulfan use 

across the industry represents a reduced risk of both on and off farm environmental contamination. 

This is important for the future development of aquaculture in cotton catchments. 

Chlorpyrifos was detected in ring tank water samples from the 02 of February to 14th of February 

2002. This event corresponded with the detection of chlorpyrifos in unpurged fish taken from both 

intensively reared stock (raceways) and free range fish. Chlorpyrifos is highly toxic to fish and also 

has the capacity to bio-accumulate and concentrate in fish (Varo et.al., 2000). LC 50 values for 

freshwater are typically below 100 μg/L, with bluegill sunfish sensitive at around 2 μg/L 

(NRA, 2000). Bio-concentration factors (BCF) for chlorpyrifos in fish are reported between 58 and 

5100 (Racke, 1993). However, despite its capacity to bioconcentrate, this compound can be rapidly 

depurated by fish if they are placed in clean water (Racke, 1993). This is typically the practice used by 

growers when purging stock prior to marketing. By placing fish in clean water growers are aiming to 

remove any off flavour taints that may be present. The monitoring of market ready Loch Eaton fish 

conducted in this study, that is the monitoring of fish that had been purged for up to 14 days, had no 

detectable level of chlorpyrifos or any other chemical residue. 

The capacity of fish to uptake and then clear chlopyrifos was demonstrated in the bio-concentration 

and depuration study. The concentration of chlorpyrifos at 25ºC reached 90 μg/kg by the 96th hour of 

exposure but was not present at detectable levels (

St George, Emerald and Dawson cotton growing regions (Muller, et.al.; 2000). Of the 103 sediment 

samples tested in that study, DDT products were detected in 74 samples (Muller, et.al.; 2000). The 

highest concentration was recorded in the Dawson River region with 240 ng/g dry weight of DDT 

detected. As stated previously, agents like DDT (DDD, DDE) are rapidly bio-magnified through the 

food chain and fish can bio-accumulate these compounds to relatively high levels as a result. As a 

consequence of their persistence in the aquatic environment, DDT, DDD and DDE have been reported 

in wild fish populations in Queensland even after their use had been banned (Roach and Runcie, 

1998). The half lives these compounds are between 3 and 15 years. The use of chlorohydrocarbon 

pesticides such as DDT was progressively banned from the 1970s with DDT being banned completely 

in Australia in 1987 (Connell, et.al., 2002). No sediment samples were analysed in this study. 

However, no DDT, DDD or DDE was detected in water or fish samples from the ring tank. The bioconcentration 

and depuration study demonstrated that if the likes of DDE was absorbed by silver perch 

it would not be eliminated during normal purging practices. This is to be expected as although DDT 

bio-transforms rapidly in fish (days) to form mainly DDE (Suedel et.al., 1994), this compound has a 

long half life in fish. The bio-concentration of compounds like DDE increases as the fat content of the 

species increases (Das et.al., 2002). As a comparison, the half life in the fat of beef cattle is 6-12 

weeks (AQIS, 1998). 

The bio-concentration study also demonstrated that other persistent OC compounds (heptachlor, 

lindane, βBHC and dieldrin) accumulate rapidly in silver perch to levels in excess of their ERLs. 

Heptachlor is highly toxic to fish with 96hr LC50 values of between 5.3 and 23 μg /L for freshwater 

and marine fish (EXTOXNETd). It has been found in fish at concentrations up to 37,000 times the 

level found in surrounding waters (WHO, 1984.). In this study heptachlor levels reached 120 times 

those in the water after 96 hrs of exposure. Similar rates of bio-concentration were observed in 

lindane, βBHC and dieldrin all of which were not eliminated during the depuration period. These 

levels are all above the ERLs set by FSANZ for these compounds in fish. 

The information from this study supports other published data concerning the bio-concentration and 

elimination of OC compounds in fish. Once contaminated, it is unlikely that the stock will be rendered 

suitable for sale. 

Despite the favourable results observed in this study and the declining volume of use of pesticides by 

the industry, the major risk to aquaculture development on cotton farms remains that of pesticide 

contamination. This risk would be highest in ring tanks that are not favourably located and where 

pesticide concentrates in run-off from fields. Ring tanks that are located in the middle of farms are at 

an increased risk of encountering spray drift issues than ring tanks that back onto riverine areas, 

undeveloped farmland or housing. Many farms have constructed ring tanks that collect from many 

sources including rivers, creeks, groundwater and also from their farms irrigation tailwater and surface 

water run-off. Using these ring tanks for aquaculture without modifying its water harvesting 

infrastructure to exclude run-off and tailwater would create risks of fish kills and/or contamination. 

Awareness of previous land and chemical use practices is clearly important as is the adoption of new 

farm management strategies that are considerate of the fish farming operation. It should be noted that 

the absence detectable levels of persistent OC compounds in either soil or water might not necessarily 

indicate a “clean” site. As demonstrated in this study and others, some compounds can bio-accumulate 

in fish to levels well in excess of environmental concentrations. 

New guidelines for the assessment of sites for aquaculture have been published by DPI&F in the guide 

‘Site identification for aquacultureassessment of chemical contamination in site selection’ (DPI&F, 

2005). 

Issues related to pesticide residues in farm produce are likely to become more apparent as 

community/consumer awareness surrounding food safety increases. Only regular, whole of industry 

based testing of aquaculture products will address consumer concerns over their safety. The only 

products that are routinely tested for chemical residues at present are those destined for export 

markets. Tuna (Thunnus maccoyii) and salmon (Salmo salar) are the only fish species that are 

incorporated in the National Residue Survey (NRS) of residues in aquaculture products at present. 

53

While further expansion of the integrated aquaculture sector is likely, this sector must continue to 

assess the risks posed by pesticide use and implement quality assurance programs to ensure its product 

is recognised as not only environmentally sensitive but is safe and of a high quality. 

54

6. Integrated Production Decision Tool 

6.1 Description 

A spreadsheet based decision tool (Fig 6.1.1) was developed during this study to enable potential 

proponents to determine the benefit and cost of diversifying their existing operations. The decision 

tool is an excel based package that enables proponents to estimate the capital investment, on-going 

operating costs, the risks and their impacts (such as the crop failure and disease), the influence on 

water quality, and fluctuation in market prices. It can aid existing farmers to develop their own 

production model and estimate the impact of investment and operational decisions on their operations 

profitability. Farmers can observe the impact of price changes on profitability for inputs such as feed, 

fingerlings, electricity, packaging and transport. It can also be used to evaluate improvements in 

genetics and other methods of stock improvement, evaluate the benefits and risks of a farms 

expansion, change in production style, or even the viability of value adding. For further information 

regarding this product please ring the DPI&F Call Centre on 13 25 23 or contact the author at 

bill.johnston@dpi.qld.gov.au 

31/05/2007 35 

Agency for Food and Fibre Sciences 

Figure 6.1.1 Example of spreadsheet based decision tool 

55

7. General Discussion 

The integration of aquaculture with cotton production using irrigation storages is a challenging one. 

The outcomes of this study demonstrate both the importance of choosing the right production system, 

placing it in the most appropriate location and managing it correctly. The location of the storage is 

common to any cage or raceway system as it impacts on the quality of water available for aquaculture 

and the potential for introduction of pesticides. Another factor governing the success of any 

aquaculture operation is the management of an integrated farm, the associated identification of training 

needs and skills development of new and existing staff. Integrated operations with shared farm labour 

will require additional investment in aquaculture training. Despite the challenges faced in this study, 

the potential for development of integrated farming in Queensland’s irrigation industry is high. The 

infrastructure and water resources that have been established by the irrigation sector are significant 

and constitute a major avenue for the growth of aquaculture in the state. 

In this study, the primary factor preventing the successful development of the aquaculture enterprise 

was the inability to adequately manage water quality. The general quality of water within the 

aquaculture ring tank was severely degraded by opportunistic riverine water harvesting events. The 

reduction in dissolved oxygen levels and increase in turbidity not only resulted in stock mortalities in 

the short term but also suppressed feeding responses and growth for extended periods. In light of this 

experience, it is recommended that future proponents of integrated aquaculture in cotton catchments 

protect themselves from similar water quality complications as the result of flood harvesting. On the 

Loch Eaton site this might be achieved by relocating the raceway structure to the adjacent ring tank. 

The site used in this study was selected because it had the most reliable water supply, did not receive 

tailwater and also had an adjacent bore water supply. However, the adjacent rink tank was built after 

this trial was established. It is similar in dimension to the existing aquaculture storage (4 ha), is 

designed to fill by overflow from the primary receiving storage and is drained through a gate valve 

located at the base of the storage. The use of this storage would enable aquaculture operations to be 

buffered from the impacts of water harvesting. It would also allow controlled application of 

flocculants to incoming water to further reduced the impact of high turbidity levels on dissolved 

oxygen concentrations within the aquaculture storage. 

While the impacts of water harvesting on water quality were significant, the use of floating raceways 

had benefit with respect to maintaining high densities of fish in a secure and serviceable structure. The 

raceway systems provided some protection against low oxygen levels and maintained high densities of 

fish. These high densities were possible because of the high rates of water exchange which was 

achieved using a low head airlift system with flow rates of up to 180 L/min/uplift. The food 

conversion ratio and growth data collected in this study indicate that while water quality did impact on 

fish growth there were clear instances where feeding practices impacted the performance on the 

system. Unlike species like barramundi (Lates calcarifer), silver perch do not typically feed at the 

surface. In this study the lack of feeding response may have impacted on the daily feeding regime. If 

the floating raceway system is to be used for silver perch production in the future, a means of more 

accurately determining when fish become satiated is required. Also, while high densities of fish can be 

maintained, the raceways must be maintained in a clean state and the fish must be monitored regularly 

to identify and manage any disease outbreaks. 

Despite problems experienced with water quality and fish growth in this study the major risk to 

aquaculture development on cotton farms is pesticide contamination. The risk is highest for ring tanks 

that are not favourably located exposing the fish to contaminated water or spray drift. The application 

of farm chemicals was managed favourably in this study. However, the potential for future 

contamination events remains, the proponents of integrated production in cotton catchments will 

benefit from the industries ongoing reduction in chemical use if it is maintained in the future. 

Therefore, while this study highlighted a number of practical issues associated with integrating 

aquaculture into a working cotton farm, it did demonstrate the potential of this approach for future 

integrated developments. 

56

The finding of this study can be summarized as: 

• Water quality was generally favourable for aquaculture although flood pumping events can result 

in detrimental increases in turbidity which lower dissolved oxygen levels. 

• The use of chemical agents such as chlorpyrifos by the cotton industry can be managed to prevent 

residue accumulation in fish farmed on cotton farms. 

• A variety of culture techniques can be used to intensively rear fish on cotton farms although 

systems like floating raceways (as used in this study) will require less water to maintain than cages 

or ponds. 

• Floating raceways (as used in this study) can maintain high densities of fish in a secure and 

serviceable environment. 

• Silver perch may not be as suited to intensive culture in floating raceways as species like Murray 

cod. 

It is recommended that irrigators seeking to introduce aquaculture into their existing farming 

enterprises investigate: 

• The impact of retaining up to 3m of water within the aquaculture storage on the farms irrigated 

crops. 

• The risk associated with servicing a new and highly technical farming enterprise. 

• The cost of additional training requirements for new and existing staff. 

• The minimum size that the aquaculture enterprise must achieve compared to the capacity that 

exists within their farm infrastructure. 

• The species that is optimal for their proposed system (extensive, semi-intensive of intensive). 

• The ability of the farm to maintain water supplies indefinitely. 

It is clear from this study that while the aquaculture potential of these regions and infrastructure is 

high, there are existing issues concerning the methods and timing of water harvesting, the species 

used, the method of farming and the associated demands on the farm operators. The level of intensity 

and scale of production must be well matched to the skill of the proponent and the available 

infrastructure. Considered placement of the aquaculture operation will determine the success of the 

operation and its ability to expand. In conclusion, the irrigation industry is well placed to invest in the 

production of additional crops from their available water resources and infrastructure, the cotton 

industry is particularly well placed because of its commitment to environmental management and 

sustainability. 

57

Appendix 

Floating Raceway Technology 

and its application in the 

Barramundi Industry 

Dr Adrian Collins 

Bribie Island Aquaculture Research Centre 

DEPARTMENT OF PRIMARY INDUSTRIES 

What is a Floating Raceway? 

• Floating raceways are in 

pond versions of traditional 

land based raceways. 

• Roto-moulded product. 

• Produced in Queensland by 

Bushman’s s tanks – Modular 

Plastic Raceways (MPR( 

MPR’s). 

58

2 medium raceways 

– 18m 3 volume 

2 small raceways 

–13m 3 volume 

Access pontoons 

Sugarland Barramundi P/L 

MPR Characteristics 

Double skinned plastic hull 

Sectional – uplift section 

– chamber sections 

Stainless steel gate frames 

Bank of air uplifts 

Serviced by land based 

blower and backup 

infrastructure 

59

Why Raceways? 

McVeigh Brothers P/L – Dalby Qld. 

Integration of aquaculture with irrigated crop 

farming as a first use of available water. 

Utilising their irrigation reservoir for fish 

culture – 5000ML of farm water storage. 

Started with net cages for production of Native 

Fish - Small cages – 2 m 3 

- Large cages – 40 m 3 

60

Problems with cages 


Predators – birds, rats and turtles damaging 

cages, resulting in mortality/stock loss. 

Fouling – Algal growth on cages required 

frequent net cages. 

Disease – Winter diseases required frequent 

salt/formalin treatment. 

Durability – Net cage material and cage collars. 

61

Alternative but Adaptable System 


Liked the security and productivity of intensive 

systems – raceways. 

Investigated the concept of floating raceways 

in their reservoir. 

Collaborated with Bushmans Tanks P/L to 

develop Plastic Floating raceways. 

62

End Screen 

Baffle Board 

Uplifts 

Water Flow (no eddy) 

25 

20 

15 

Flow (cm/sec) 

10 

5 

0 

-5 

-10 

110 

100 

80 

Depth (cm) 

60 

40 

20 

1 

210 

360 

510 

60 

660 

Distance (cm) 

64

Water Flow (eddy) 

Flow (cm/sec) 

35 

30 

25 

20 

15 

10 

5 

0 

-5 

-10 

-15 

110 

100 

80 

Depth (cm) 

60 

40 

20 

1 

160 

60 

260 

360 

460 

560 

660 

Distance (cm) 

65

External screen 

Air supply chamber 

External screen 

Internal screen 

66

End gates - changeable 

67

Barramundi Trials 

• Sugarland Barramundi P/L 

Four MPR’s to be stocked with varying 

densities and size classes of fish. 

The MPR results to be compared to cage 

controls. 

Performance of fish (growth, FCR, survival, 

disease). 

Productivity comparison (labour to yield) and 

cost benefit analysis. 

Barramundi Trials – MPR’s 


2 small raceways - Stock on 24/5 with 35g fish 

- 3200 fish each 

- Density = 8kg/m 3 

Target SR’s – 200g average at a density of 50kg/m3 

2 medium raceways - Stocked on 18/6 with 120g fish 



Target MR’s – 600g average at a density of 80kg/m3 

68

35 g average fish – 3200 each 

120 g average fish – 2300 each 

Barramundi Trials – Cages 


2 Net Cages - Stock on 24/5 with 35g fish 

(control for 2 small raceways) 



Target SR’s – 200g average at a density of 25kg/m3 

2 Net Cages - Stocked 18/6 with 120g fish 

(control for 2 medium raceways) 



Target MR’s – 600g average at a density of 40kg/m3 

69

System Cages MPR’s 

Stocking 

Capacity 

Densities for fingerlings – 50 kg m -3 

Densities in small net cages may reach 50 kg 

net cages typically operate at 10 kg m kg m -3 100 kg m -3 

m -3 for market sized fish while larger circular Densities for plate sized fish up to 

Grading 

Feeding 

Fish Health 

Security 

Operation 

Durability 

Cost Benefit 

Fish have to be hand graded or pumped to a 

grading machine. 

Feed waste through wind, wave action and 

loss through floor. 

Fish must be removed from nets or nets 

bagged requiring high labour input and stress 

to fish. 

Predators/vermin can damage cages or fish 

directly and result in stock mortalities or 

escape 

High density cages still require paddle wheels 

to aerate and move water. 

Cages must be regularly cleaned, repaired 

and replaced. 

Relatively cheap to set up but limiting in 

productivity with relatively high ongoing 

operational and labour costs. 

Fish can be graded within the 

raceway using a ‘push grader’ or 

‘slide gate’. 

Feed can be accurately delivered 

with uneaten feed easily observed.. 

As with tanks fish can be treated and 

observed without removing or unduly 

stressing them. 

Predator and vermin proof. 

The blower serves to operate the 

airlifts which moves water more 

efficiently than paddlewheels. 

MPR are made from materials with a 

20yr life. 

Capital requirement but potentially 

improved profitability. 

Potential Uses of MPR’s 

Nursery System 

Can MPR’s hold larger numbers of fingerlings 

and juveniles rather than in tanks/cages? 

Growout System 

Can Barramundi be grown in MPR’s at density 

to plate size? 

What are the cost benefits and industry implications? 

70

Paul McVeigh 

Mark Fantin 

Doug Young 

71

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76




RIRDC Publication No. 09/060 

There are many thousands of hectares of water storage on 

cotton farms in Australia. This report shows how the water 

infrastructure developed by the cotton industry for such large 

scale irrigation may also have potential for development of 

aquaculture. The introduction of an additional cropping 

opportunity may have significant economic, environmental 

and social benefits. It does however, also face several 

operational challenges that stem from the need to manage 

these water bodies and the farm’s other activities in a more 

intensive and considered fashion. 

This report is targeted at irrigators who may be interested 

in diversifying their business by integrating commercial 

aquaculture with irrigated agriculture. It focuses on a 

demonstration site in the cotton industry in Queensland, 

but contains valuable information for potential investors 

throughout Australia. 

The Rural Industries Research and Development Corporation 

(RIRDC) manages and funds priority research and translates 

results into practical outcomes for industry. 

Our business is about developing a more profitable, dynamic 

and sustainable rural sector. Most of the information we 

produce can be downloaded for free or purchased from our 

website: www.rirdc.gov.au, or by phoning 1300 634 313 (local 

call charge applies). 

Most RIRDC books can be freely downloaded 

or purchased from www.rirdc.gov.au or by 

phoning 1300 634 313 (local call charge 

applies). 

www.rirdc.gov.au 

Contact RIRDC: 

Level 2 

15 National Circuit 

Barton ACT 2600 

PO Box 4776 

Kingston ACT 2604 

Ph: 02 6271 4100 

Fax: 02 6271 4199 

Email: rirdc@rirdc.gov.au 

web: www.rirdc.gov.au

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