Carp (Cyprinus carpio). Photo courtesy of Gunther Schmida

Queensland has the highest diversity of freshwater fish in Australia. Unfortunately this diversity is threatened by the presence of pest fish (sometimes referred to as 'non-indigenous'), which have successfullly established in some of our waterways. Some pest fish pose such a threat to Queensland waters that they have been declared as 'noxious' in fisheries legislation.

Pest fish and noxious fish

Pest fish are fish species that are not native to an area and have potential negative social, economic or environmental impacts. Most pest fish established in Queensland waters have been released by irresponsible members of the public.

A noxious fish is one that has been declared as harmful by state statute law because they are, or may become, a serious pest to native aquatic communities. Noxious fish have characteristics that are detrimental to other fish, aquatic habitats or humans. They must not be used to stock dams or keep in aquariums. Penalties of up to $200,000 apply.

Some non-indigenous fish species are can be kept in privately owned aquariums and ponds provided they cannot escape into any other waterways (e.g. they cannot be kept in a dam if it may overflow into a river, creek, etc. during a flood). Check the prescribed list of non-indigenous fish that you can keep without a permit (link under 'Further information' below).

Why are pest fish harmful to the environment?

The introduction of pest fish species into Queensland's natural waterways may reduce native fish numbers. Pest fish affect native fish through direct competition for food and space, predation, habitat alteration and the introduction of exotic diseases and parasites.

What to do if you catch a tilapia or carp

If you catch a noxious fish, kill the fish as quickly and humanely as possible. Fisheries Queensland advocates the 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.

It is an offence to have noxious fish (such as carp and tilapia) in your possession, either dead or alive (except dead Nile perch). You must therefore dispose of the fish as soon as practicable after killing. It is recommended that you do this by burying it a suitable distance from the waterway where it was caught or disposing of it in a rubbish bin.

Banned as bait

You cannot use noxious or non-indigenous fish as bait. These fish must not be returned to the water dead or alive.

What is Fisheries Queensland doing?

Fisheries Queensland is investigating the effectiveness of a number of methods for controlling pest fish, without impacting on the native fish stocks. These methods include:

• restoring native fish habitats (in conjunction with a number of community groups)
• physically removing pest fish (such as line fishing and selective netting)
• using fish poisons (piscicides) that will break down rapidly
• investigating methods to decrease the numbers of young being produced (e.g. disturbances to breeding behaviour, the use of hormones and genetic manipulation).

Legislation exists under the Fisheries Act 1994 for the management of noxious and non-indigenous fishes in Queensland waters. Fines of up to $200,000 can be imposed on anyone having noxious fish in their possession without a permit or persons convicted of releasing non-indigenous species. Additional penalties may be imposed to cover the cost of eradication measures.

Fisheries Queensland is also undertaking educational campaigns to increase awareness of the problem.

For further information on what Fisheries Queensland is doing to control pest fish, see Control of exotic pest fishes - an operational strategy.

How you can help

To help stop the spread of pest fish:

• learn how to identify pest fish
• avoid spreading pest fish between waterways
• report sightings of pest fish.

To report illegal fishing activities in Queensland, phone the Fishwatch Hotline on 1800 017 116.