A 'pest fish' is either a native or exotic fish that has a negative impact on species living in the region. General impacts include disease, predation, competition for food and habitat, and degradation of habitat and water quality. Throughout Australia, millions of dollars are spent annually in attempts to control or eradicate invasive pests.
Tasmania has strict legislative and quarantine procedures designed to minimise accidental introductions of exotic plants and animals in order to protect native fisheries and the integrity of Tasmania's aquatic ecosystems. The Inland Fisheries Act 1995 covers the entry into Tasmania, of any fish species capable of living or breeding in the State's waters. This includes imports made for fish bait, aquarium pets and aquaculture.
A number of Prohibited Activities under the legislation attract large fines of up to $25,000 depending on the number of offences.
As some fish species have the potential to seriously damage the environment and displace native species, they have been declared 'controlled fish' under the Act. This applies to all species of mainland yabby (Cherax spp.), European carp and Eastern gambusia. Strict penalties apply for the unlawful possession of these species or their release into any inland water in Tasmania (including an aquarium). Provisions under the Act also allow the IFS to regulate all freshwater fish, crustaceans, amphibian, mollusc, invertebrate and aquatic plant imports. Hence, all imports, whether for recreational, hobby or commercial purposes, must have the written authority of the IFS.
Pest fish management covers the monitoring, control and eradication of identified pest fish species, with the priority being those identified as 'controlled fish', including European carp, yabbies and Eastern gambusia. The aim of management for the other acclimatised fish that are considered undesirable is to prevent the spread of these species outside their present distribution within the State.
Pest Fish Impacts
Exotic fish, or the water in which they are kept, if released into the environment, may harm native and recreational fisheries, the aquaculture industry and the ecological integrity of the aquatic systems. They can:
- destroy native or recreational fisheries by establishing breeding populations which compete for food and habitat;
- spread diseases which may infect native fish or other aquatic animals;
- spread parasites either directly with imported fish, or indirectly with the holding water or with exotic aquatic plants which may carry animals (eg. Water snails which harbour parasites of livestock);
- alter habitat which may displace and reduce populations of native fish and trout (eg. European carp destabilise bank vegetation and cause water quality deterioration – muddied streams and lakes);
- cause other problems such as introduction of noxious weeds which may thrive in rivers, creeks, lakes and irrigation channels, choking waterways, blocking drains and impeding navigation.