Freshwater pests and diseases

Introduced freshwater species like didymo, koi carp, oxygen weed, and hornwort threaten New Zealand's waterways. Learn about what we're doing to stop the spread of freshwater pests.

About freshwater pests and diseases

Managing and preventing the spread of freshwater pests and diseases is important to protect our native species and local economies.

Freshwater pests can have significant impacts on:

  • commercial fisheries
  • water intakes for irrigation and hydro power generation
  • drinking water
  • recreation and tourism
  • loss of native species
  • water management costs.

What we're doing about them

We're working with organisations like regional councils, the Department of Conservation (DOC), Fish and Game, Land Information New Zealand, iwi, and energy companies to prevent the spread of freshwater pests and diseases.

Through the National Interest Pest Responses (NIPR), we're trying to eradicate freshwater pest plants like hydrilla, salvinia, and phragmites.

Several agencies are working with us to manage and prevent the spread of freshwater pests and diseases:

You also need approval to possess some live freshwater pest species.

Anyone knowingly moving freshwater plants or animals that are unwanted organisms between waterways will need to apply for permission.

Possession of freshwater species

You need approval to possess certain freshwater species, and different agencies are responsible for different species. You’ll need to get in touch with:

  • MPI – for catfish and pest plants
  • Department of Conservation (DOC) – for koi carp, rudd, grass and silver carp, and any noxious species
  • Fish & Game – for gambusia, rudd, trout and salmon

Find out more on the DOC website:

Check, Clean, Dry

The Check, Clean, Dry campaign encourages recreational water users to check, clean and dry their equipment (including items like wetsuits) and vehicles when moving between waterways.

Freshwater Biosecurity Partnership Programme

The Didymo long-term management plan was established in 2007. In 2016 the plan was formally renamed to the Freshwater Biosecurity Partnership Programme incorporating all freshwater pests.

The programme works to understand and manage regional and national pathways through which significant freshwater pests are spread. This is a partnership programme and is focused on building effective relationships, increasing knowledge about the issues, best practice for management, sharing expertise, and leading the Check, Clean, Dry campaign.

Who to contact

If you'd like to learn more about freshwater pests and diseases, email

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