The goldfish is a pest fish if released into a waterway.
What is a pest fish?
A pest fish is a fish that is:
- declared a prohibited noxious fish under Queensland legislation or;
- declared a restricted noxious fish under Queensland legislation or;
- an escaped or released ornamental fish or;
- an escaped or released game fish or;
- a released native fish that is not native to the area it has been released.
Impacts to native fish
The introduction of pest fish often leads to the reduction of local native fish. This is because the pest fish compete with native fish for food and space. They may also be aggressive, cause habitat disturbance and introduce diseases, which the native fish are not used to.
Ornamental fish can become pest fish when they are released into water ways and dams. Guppies are native to South America and the Caribbean and probably escaped from fish tanks into the wild to become pest fish. In the wild, guppies breed very rapidly and efficiently and compete with native fish for food and space.
Pest fish that have successfully invaded Australian waters have 1 or more of the following attributes:
- Wide environmental tolerances
- Flexible food requirements
- High reproductive output
- Early maturation
- Aggressive behaviour
- Lack of predators and competitors.
Pest fish often inhabit and flourish in disturbed waterways (e.g. stagnant creeks, drains) as these often have abundant food resources and lack native fishes because of harsh and changed environmental conditions.
Preventing pest fish being introduced to our waterways
Unless you have a permit, it is an offence to stock your farm dam with fish that do not occur naturally in your area. Stocking the wrong fish in your dam may lead to irreversible changes to local fish populations if the fish escape from your dam during floods.
You are allowed to put goldfish and other ornamental fish that are allowed to be kept in aquariums (i.e. not prohibited or restricted noxious fish), into ornamental ponds, as long as they cannot escape during high rainfall. A better alternative would be to put native fish in your pond. Native fish are great for ponds as they are good for mosquito control, have interesting colours and shapes and some of the larger species have their own personality. Find out the natural range of Queensland freshwater species.
Never dump your aquarium contents into waterways or flush it down the toilet, as the water will eventually end up in our waterways.
- Don't transfer pest fish between waterways—don't use pest fish as bait.
- Obtain a permit to stock fish. Buy fingerlings from a registered hatchery to minimise the chance of contamination with undesirable species.
- Don't return pest fish to the water. If you catch a pest fish, kill it humanely and dispose of it appropriately.
- Prevent unwanted hitchhikers—check, clean and dry your boats and gear between waterways.
Ornamental fish enthusiasts and backyard pond owners
- Don't dump fish—give unwanted aquarium fish to friends or a pet shop instead of letting them go in the wild.
- Prevent accidental escapes—screen outdoor ponds to prevent overflow during heavy rains.
- If possible, keep native fish instead of exotics—contact your local aquarium or Fisheries Queensland on 13 25 23 for information on local native fish species.
- Find out the natural range of Queensland freshwater species.
- Prevent accidental escapes—comply with aquaculture permit conditions designed to prevent the escape of fish (e.g. screened water outlets).
- Don't experiment with exotics—keep to the prescribed species list.
If you no longer want fish that are in your aquarium, see if your local pet shop will take them. If not, Biosecurity Queensland advocates following ethical euthanasia protocols recommended by the 2001 ANZCCART publication Euthanasia of animals used for scientific purposes. The most appropriate method may involve stunning the fish via a sharp blow to the back of the head causing brain destruction.
Do not transport fish between catchments to use as bait. Live bait may escape and dead bait may still be holding viable eggs.
Removing pest fish once they have established
Once pest fish have established in a waterway, it is very difficult - if not impossible - to remove them. It is much better to prevent their introduction and/or spread by educating people about the negative impacts of pest fish.