Our work Animals in Aotearoa Fishes Fish farming in New Zealand

Fish farming in New Zealand

Salmon farming is big business in New Zealand and is expected to expand in the coming years. Most farmed salmon is produced in marine environments in the Marlborough Sounds and Stewart Island. The species farmed in New Zealand is the non-native Chinook salmon, also known as King salmon.

The salmon are reared in land-based hatcheries and then transferred to sea cages or fresh-water farms. To make them grow quickly, salmon are fed a synthetic diet fortified with fishmeal and fish oil. They generally reach slaughter size after ten to eighteen months. Around 50 percent of salmon farmed in New Zealand is exported, with Japan and Australia being the biggest markets.

Invasive and dangerous farming methods

The repetitive manipulation of farmed fish is a major cause of stress and pain. Salmon need to be constantly sorted by size and separated, as trapped bigger fish will bully smaller fish. Other invasive practices include vaccinations, loading, transportation and breeding techniques in which the male is brutally stripped of sperm and the female of eggs.

Farmed fish are liable to suffer high mortality rates from injury and disease, and they are also vulnerable to predators and other hazards. In one incident in 2010, thousands of fish were killed when jellyfish floated into a salmon farm. Attacks from seals are also an issue on New Zealand fish farms.

Environmental damage

There is a perception that fish farming relieves the pressure on wild fish populations. Unfortunately the opposite is true. Wild fish are caught and used to feed  farmed fish, which contributes to the threat to the biodiversity of our oceans. Additionally, all waste from fish farms goes untreated into the sea. Advertising for  salmon farming talks about “the pristine waters of the Marlborough Sounds,” but as operations become bigger so do the levels of pollution. Waste in the water also encourages the growth of algal bloom, resulting in depleted oxygen levels and poor water quality.

By definition, fish farming is not ‘sustainable.’


In fish farms, high numbers of fish are crammed into unacceptably small spaces. Overcrowded cages deprive salmon of the freedom to swim long distances and to carry out the natural social behaviours they would in the wild. Physical injuries, abnormalities and blindness are common. Keeping high numbers of fish in crowded conditions also encourages the spread of infectious diseases and parasites such as sea lice.

Inhumane methods of slaughter

Salmon would naturally live around three to four years. Farmed fish are routinely starved for days before slaughter to empty the gut. Approved slaughter methods include leaving the fish out of water, electrical stunning and brain spiking. A few farming operations anaesthetise salmon before slaughter, but many do not.

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