Find out about some of the pest fish found in New Zealand and why they are a problem for our freshwater ecosystemss.

    Freshwater ecosystems are vulnerable to invasion by pests and weeds because it is very hard to detect them until they are a problem. In recent years there has been a rapid expansion of some species of introduced freshwater fish.

    Once pest fish have invaded a waterway and become established it is very difficult to remove them because they are able to spread through a whole river catchment. It is very important to prevent pest fish from invading into places where they aren’t already.

    Pest fish species

    There are 23 species of introduced fish in New Zealand. Like all introduced species, they have some impact, but some cause more problems than others.

    Find out about some of the introduced fish species in New Zealand:

    Aquarium species that have escaped into the wild are of growing concern. Don’t empty your aquarium into your local stream, as your pets can become pests.

    Impact of pest fish

    Many people are unaware of the damage done to our waterways by pest fish. Unfortunately some types of introduced fish have spread into the wild, become pests and are threatening New Zealand’s freshwater species and environments by:

    • Stirring up sediment and making the water murky
    • Increasing nutrient levels and algal concentrations
    • Contributing to erosion
    • Feeding on and removing aquatic plants
    • Preying on invertebrates, native fish and their eggs
    • Competing with native species

    Invasive fish management

    DOC has a programme of survey, education, signage and, in some situations, eradication of pest fish where it is possible. DOC works with other agencies to manage invasive fish but unfortunately once pest fish become established in a waterway it is often difficult to remove them. 

    Get more information in the New Zealand invasive fish management handbook.


    There is a variety of legislation that governs freshwater fish in New Zealand, designed to protect our freshwater environments from alien pests.

    The approval of Fish and Game New Zealand is required to hold live sportsfish and Gambusia, or introduce fish or fish eggs to sportsfish or game bird habitats. 

    Conservation Act 1987 To introduce any aquatic life (native or introduced fish, plants or invertebrates) into an area where they don’t already occur, you need a permit from the Minister of Conservation, otherwise you could be liable for a fine of $5,000. The taking and holding of some fish requires a special permit from the Ministry of Primary Industries.

    Unwanted Organisms (Biosecurity Act 1993) It is illegal to release, spread, sell or breed unwanted organisms. There is a $100,000 fine or five years imprisonment for people caught doing so. 

    Noxious Fish (Freshwater Fish Regulations 1983) People who possess, control, rear, raise, hatch or consign noxious fish without authority are liable for a fine of $5,000. Both koi carp and rudd are classified as noxious fish, except within the Auckland/Waikato Fish and Game Region where rudd are classified as a sportsfish. 

    You can help

    Fish can’t walk. These fish are spreading into places where they haven’t been recorded before. People are illegally spreading them around both accidentally and on purpose

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