For a number of years the DPI&F has been investigating the potential for developing aquaculture within Queensland’s inland communities, particularly to add further value to the water resources of existing agricultural and industrial operations.
Industry partnerships have been fostered to enable this developmental work, with current projects supported by the Cotton Catchment Communities CRC, Arrow Energy N/L and McVeigh Enterprises P/L.
Cotton-farming areas in the Dalby region overlap major natural gas reserves within underground coal seams, which are now being commercially exploited. A feature of CSG operations is the necessary uplift of associated water from the coal beds to liberate the adsorbed methane gas.
The water brought to the surface is slightly salty, similar to the water within the region’s aquifers, and therefore unsuitable for many direct beneficial uses. CSG water represents a potentially significant resource for aquaculture; however, this potential needs to be measured against the actual suitability of the infrastructure and water source for the purpose of farming fish.
Analysis of water chemistry at a potential trial site at Kogan revealed a unique ionic profile. The water is low in potassium, calcium, magnesium and sulphate and 10 times higher in bicarbonate than seawater at the same dilution.
Bioassay trials have been completed to determine water quality effects on acclimation, growth and survival of Murray cod, mulloway and barramundi, and trials have shown that raw CSG water is unsuitable for the production of these fish species; however, with the addition of potassium, fish grew equally as well as experimental controls.
This important osmoregulatory ion (K+) is simple to administer, cost-effective and typically required in groundwater aquaculture operations in Australia.
Further implications of other ion deficiencies, however, will have a bearing on the type of production system used to culture the fish in CSG water. For instance, trials showed that as salinity increases to above 8 parts per thousand, calcium is additionally required due to its positive effect on membrane permeability.
To successfully add calcium to CSG water (in order to prevent calcium carbonate precipitation), the pH level needs to be reduced to below 8.3. While this can be achieved with the addition of sulphuric acid, it is logistically diffcult and likely to be cost-prohibitive to implement on a large scale.
Establishing a large-scale demonstration floating raceway system (based at Arrow Energy’s Kogan evaporation dam) appears unlikely due to these inherent diffculties. A more viable fish production system at this site would seek to use the water before salinity concentrates in the evaporation dam. Discussions continue with project partners to advance aquaculture development in this area.
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