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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
Page 1: Integrated Agri-Aquaculture Demonst
Page 4 and 5: © 2009 Rural Industries Research a
Page 6 and 7: Acknowledgments The authors would l
Page 8 and 9: Contents Foreword .................
Page 10 and 11: Table 4.3.11 Table 4.3.12 Table 4.3
Page 12 and 13: Executive Summary What the report i
Page 14 and 15: crop. This is much higher than simp
Page 16 and 17: documented such waters types as bei
Page 18 and 19: 2. Demonstration Farm 2.1 Backgroun
Page 20 and 21: Figure 2.2.3 Net cages used for sil
Page 22 and 23: 3. Water Use and Quality 3.1 Backgr
Page 24 and 25: inland Australia with high levels o
Page 26 and 27: Table 3.3.3 Average monthly afterno
Page 28 and 29: 169 165 161 157 153 149 145 141 137
Page 30 and 31: In February 2001, enough water was
Page 32 and 33: 4. Production Systems and Growth 4.
Page 34 and 35: Figure 4.2.3 The first 7m 3 floatin
Page 36 and 37: Figure 4.2.7 Uplift, baffle board a
Page 38 and 39: float to prevent drowning of air br
Page 40 and 41: Figure 4.2.13 Raceway push gate gra
Page 44 and 45: Table 4.3.3 The length of culture p
Page 46 and 47: Stock retention was also high in th
Page 48 and 49: Table 4.3.10 The length of culture
Page 50 and 51: 4.3.5 Disease Detection and Treatme
Page 52 and 53: The average rate of growth for silv
Page 54 and 55: R E Figure 4.4.1 Existing (E) and r
Page 56 and 57: 5. Pesticide Monitoring and Residue
Page 58 and 59: 5.2.1.1 Pesticide Application and U
Page 60 and 61: prior to the commencement of the tr
Page 62 and 63: 5.4.2 Pesticide Bio-concentration a
Page 64 and 65: 0.4 0.35 0.3 0.25 ug/L 0.2 0.15 0.1
Page 66 and 67: There were no detections of endosul
Page 68 and 69: While further expansion of the inte
Page 70 and 71: 7. General Discussion The integrati
Page 72 and 73: Appendix Floating Raceway Technolog
Page 74 and 75: Why Raceways? McVeigh Brothers P/L
Page 76: Alternative but Adaptable System Mc
Page 79 and 80: Water Flow (eddy) Flow (cm/sec) 35
Page 81 and 82: End gates - changeable 67
Page 83 and 84: 35 g average fish - 3200 each 120 g
Page 85 and 86: Paul McVeigh Mark Fantin Doug Young
Page 87 and 88: Das, B., Sharif, Y., Khan, K., Das,
Page 89 and 90: Müller , J.F., S Duquesne, Jack. N
Page 91: Integrated Agri-Aquaculture Demonst

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