Pest Fish Species
Three species of pest fish in Tasmania - European carp, mainland yabbies and Eastern gambusia - are classified as 'controlled fish' under the Inland Fisheries Act 1995, which means they have the potential to cause significant environmental harm. Three other fish species - goldfish, redfin perch and tench - are regarded as undesirable pests. The distinguishing features of these species enables Pest Fish identification.
Carp were first discovered in North West Tasmania in 1975 and again in 1980. These populations were subsequently eradicated by poisoning. Carp were again discovered in Tasmanian waters in 1995 this time in lakes Crescent and Sorell. They have not been found in any other Tasmanian waters since this latest discovery. Carp are currently managed by the IFS to contain them to these two waters, and ultimately eradicate their population in Tasmania.
All species of mainland yabbies (Cherax.spp) are listed as controlled fish. The only species found in Tasmania is Cherax destructor, which was first released in Tasmania’s midlands, and has since been transported to farm dams and waterways around the State. Yabbies have the potential to out-compete native crayfish and, due to their burrowing habits, have been blamed for dam failures.
First discovered to be in Tasmania in 1990, there are currently several self sustaining populations in the upper reaches of the Tamar estuary. The largest population of Gambusia can be found in the Tamar Island Wetland Reserve Conservation Area where there is unrestricted access to the main estuary. Gambusia are an annual species with enormous reproductive capacity. An average female is able to give birth to up to 450 live young over the summer breeding season. Gambusia is a threat to Tasmania’s native fish and frogs because of its superior competitive abilities and its extremely high tolerance to a wide range of environmental conditions.
Goldfish show considerable colour variation in captivity, but in the wild tend to revert to their natural colour of olive green to golden bronze. Most Tasmanian populations are a result of releases from aquariums and are locally abundant in farm dams and some streams. They are believed to compete with native fish and have the potential to spread fish diseases and parasites.
Redfin perch were introduced soon after trout in the 1860’s. Over the past 30 years, redfin have spread to some of Tasmania's trout waters and into areas of high conservation significance. Redfin have been directly linked to declining trout fisheries and native fish distributions, and are capable of forming large unmanageable populations.
Tench were introduced into Tasmania from Europe and were well established by the 1880’s. They are usually dark olive green in colour with orange red eyes. They are now widespread in Tasmania. Tench are believed to directly compete with trout and native fish for food.
Pest Fish Fact Sheets
Fact Sheet for Eastern gambusia (Gambusia holbrooki)
Fact Sheet for european carp (Cyprinus carpio)
Fact Sheet for goldfish (Carassius auratus)
Fact Sheet for redfin perch (Perca fluviatilis)
Fact Sheet for tench (Tinca tinca)