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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
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