New Zealand’s marine ecosystems and species are highly diverse. About 8000 marine species have been found in New Zealand waters, including 964 species of fish, 2000 species of molluscs (snails, shellfish, and squid), 400 species of echinoderms (kina and starfish), and 900 species of seaweed.

A fisheries quota management system (QMS) was put in place in 1986, and since then indicate QMS stocks have above sustainable levels. However, for over half the species managed under the QMS, too little is known to be able to assess whether harvesting levels are sustainable.

For several species where information is available, stocks have been depleted below levels judged to produce maximum sustainable yields, but management strategies are in place to rebuild these stocks to sustainable levels.

Shellfish and some other marine invertebrates remain vulnerable to over-harvest and habitat degradation, caused by sediment from rivers, pollution, changes in sea temperature, and fishing activities.

Although New Zealand’s coastal waters and habitats are generally held to be of high quality by international standards, they are under stress in some areas, particularly near large estuarine towns and cities and the mouths of large rivers. Estuarine and marine ecosystems are also threatened by the invasion of exotic species – a problem aggravated by vessels transporting ballast water, and hull encrustations.