Story: Marine invaders

Page 5. Preventing future invasions

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Marine biosecurity

A number of agencies are involved in the prevention, detection and management of marine invasives. The Biosecurity Act 1993 gave the Ministry of Fisheries tools to control the introduction of exotic organisms into New Zealand’s coastal waters. In 2004 many biosecurity responsibilities were taken over by the Ministry of Agriculture and Forestry’s new authority – Biosecurity New Zealand.

The Ministry for the Environment, the Department of Conservation, the Ministry of Health, the Environmental Risk Management Authority, and regional councils are also involved. These agencies develop policy guidelines, enforce legislation, monitor at-risk areas and control or eradicate pests at a local or national level.


The Ministry of Fisheries has made a list of six of the most unwanted marine pests, which would be far more damaging than those already in residence. These have had a severe impact on environments similar to New Zealand’s. They are:

  • Mediterranean fanworm (Sabella spallanzanii)
  • European shore or green crab (Carcinus maenas)
  • northern Pacific sea star (Asterias amurensis)
  • Chinese mitten crab (Eriocheir sinensis)
  • seaweed caulerpa (Caulerpa taxifolia)
  • Asian clam (Potamocorbula amurensis).

Preventing accidental introductions

There are national and regional laws and guidelines to cover high-risk practices such as the discharge of ballast water and the transfer of organisms on hulls.

Ballast water discharge

To reduce the risk of transferring unwanted organisms, ships coming into New Zealand are required to exchange ballast water taken near land with water free from coastal influences. This must be taken at least 200 nautical miles from land, and in water over 200 metres deep.

Hull fouling

A variety of fouling species are able to attach themselves and grow on ships’ hulls. Unwanted organisms can enter New Zealand waters in this way. In 1995, one Russian super trawler had 90 tonnes of foreign organisms, including mussels, sponges, goose barnacles, seaweed and anemones, removed from its hull in the Devonport dry dock. Most hulls are regularly treated with anti-fouling products, because fouling considerably reduces speed and increases fuel costs. However, wear and tear can reduce the effectiveness.

Fouling organisms can be inadvertently released in a number of ways – during hull cleaning, by becoming dislodged accidentally, or during the reproductive stage. There are guidelines and regulations to reduce these risks.

Monitoring and surveillance

High-risk areas such as major international ports are routinely monitored by marine biologists to identify any new unwanted organisms. The public are also asked to watch for invasives. Poster campaigns and websites are targeted at people involved in marine activities.

Control and research

When pests are identified, the difficulty and cost of control or eradication are weighed against the potential harm from the spread of the organism. In some cases, the only effective way to eradicate a pest from an area is for divers to remove each specimen by hand.

As well as the agencies involved in marine biosecurity, the National Institute for Water and Atmospheric Research, the Cawthron Institute and most New Zealand universities carry out research into all aspects of marine bioinvasions. There is also collaboration with Australian research institutes on issues common to both countries.

How to cite this page:

Christina Troup, 'Marine invaders - Preventing future invasions', Te Ara - the Encyclopedia of New Zealand, (accessed 17 April 2024)

Story by Christina Troup, published 12 Jun 2006