There are various methods available within the Queensland finfish aquaculture industry to ensure that life stages of cultured animals are not released into natural waterways and wetlands. Finfish aquaculturists must ensure that no life stages of cultured animals (endemic or non-endemic) are released into natural waterways or wetlands from a finfish aquaculture facility.
At a minimum, escape prevention mechanisms must include the following:
- The screening of pond/tank discharge structures with an appropriately sized mesh;
- The screening of farm discharge structures with an appropriate sized mesh.
Harvesting:
The various harvesting methods employed throughout the Queensland finfish aquaculture industry have the potential to impact on the environment indirectly in varying degrees. Finfish aquaculturists must utilise a harvesting method which minimises the suspended solid and nutrient loading of discharge waters and the potential of fish to escape from the facility.
Harvesting practices may include:
- The use of nets and traps;
- Trawl harvesting;
- Drain harvesting.
Methods for reducing suspended solids and nutrient levels in discharge waters may include:
- In the case of net, trap and trawl harvesting, allowing an appropriate time after harvesting before discharging water, to allow suitable time for particulate nutrients and suspended solids to settle to the pond floor.
- In the case of drain harvesting, ensuring that adequate erosion controls are in place from the pond discharge points.
- The use of settlement ponds or drains. Additionally in the case of drain harvesting, adequate screening and apparatus must be used to reduce the risk of unintentional fish escape.
Translocation:
The translocation of fish within Queensland waters has occurred to create recreational fisheries in artificial impoundments, by escape from aquaculture facilities and from the release of fish into farm dams. The potential for finfish aquaculturists to introduce non-endemic or exotic species into Natural waterways or wetlands must be removed entirely.
The potential for translocation surrounds several areas of operation:
- escape from the facility;
- intentional release of non-endemic species by the finfish aquaculturist;
- contamination of consigned fish;
- a purchaser (through stocking of farm dams or waterways);
- final product recipient (retail customers).
Escape:
Translocation of species has the potential to occur where non-endemic species have been approved for culture, through the escape of individuals with waste waters, loss of stock through flooding and overflow of ponds/tanks or pond wall failure. There are several practical techniques to avoid the escape of individuals from ponds/tanks. In order to prevent escape, finfish aquaculturists must, where applicable, undertake the following:
- Construct ponds to ensure the top of pond walls are above the 1 in 100 year flood level;
- Provide adequate screening of pond/tank discharge structures;
- Maintain adequate pond/tank freeboard levels;
- Install adequately screened pond/tank overflow structures;
- Maintain screens and pond/tank discharge structures on a regular basis;
- Install and maintain adequate secondary screens on facility discharge structures, where waste waters may enter public waters;
Additionally, non-endemic live feeds must not be used where there is the potential for the feed species to escape and reproduce in the environment.
The culture of some species in certain locations may require further more advanced techniques. These may include:
- The installation of fish-proof strainer dams;
- The installation and maintenance of gravel filtration on pond discharge structures;
- Chemical treatment of water released from hatcheries.
Information Prepared By:
Dallas J Donovan
Information Sourced From:
