Aquaculture in New Zealand - Cultured Species - Salmon

Salmon

Around 1900, different salmon were introduced as sport fish. Only the king salmon (Chinook) adapted to the environment. For decades, the development of salmon and trout aquaculture in New Zealand was opposed by recreational fishers, on the grounds that disease would spread from fish farms into recreational fisheries, and that wild fish would be poached if they could be sold. In 1973 the government compromised by making trout farms illegal, but salmon farms legal. New Zealand is probably the only country in the world where trout farming is illegal, despite commercial interest from companies already farming salmon.

In 1976, the first salmon farm was established at Pupu Springs, Tasman. Salmon were raised in fresh water, growing to 25 centimetres over two years. The venture was originally aimed at ocean ranching, where juvenile salmon would be released into the sea with the expectation that some would return as adults. But few did return, so the Pupu Springs facility was converted to a hatchery, supplying stock to sea farms.

In 1983, the first sea-cage salmon farm was established in Big Glory Bay, Stewart Island. It was followed by farms in the Marlborough Sounds and at Akaroa Harbour on Banks Peninsula. These areas accounted for over 90 percent of the 8,500 tonnes of salmon produced in 2001.

Today, New Zealand accounts for over half of the world production of king salmon (7,400 tonnes in 2005).

Farming in the sea (mariculture) for king salmon is sometimes called sea-cage ranching. Sea-cage ranching takes place in large floating net cages, about 25 metres across and 15 metres deep, moored to the sea floor in clean, fast-flowing coastal waters. Smolt (young fish) from freshwater hatcheries are transferred to cages containing several thousand salmon, and remain there for the rest of their life. They are fed fishmeal pellets high in protein and oil. Most of this fishmeal is imported from Australia. The salmon are harvested when they are about two years old, weighing 2.5 to 4 kilograms. Sea cages are located in the Marlborough Sounds, Akaroa Harbour and Stewart Island.

Farming in freshwater for king salmon uses net cages placed in rivers, using techniques similar to those used for sea-farmed salmon. Freshwater raceways are located in several Canterbury rivers such as the Clutha and Waimakariri Rivers. In the 1990s, a unique form of freshwater salmon farming was developed in hydroelectric canals in the Mackenzie Basin. Young salmon are enclosed in pens in the Ohau and Tekapo canals. The Tekapo site, fed by fast cold waters from the Southern Alps, is the highest salmon farm in the world, 677 metres above sea level.

Before they are killed, cage salmon are anaesthetised with a herbal extract. They are then spiked in the brain. The heart beats for a time as the animal is bled from its sliced gills. Relaxing the salmon like this when it is killed produces firm, long-keeping flesh. Lack of disease in wild populations and low stocking densities used in the cages means that New Zealand salmon farmers do not use antibiotics and chemicals that are often needed elsewhere.

The New Zealand industry has grown into the largest producers of farmed king salmon in the world, accounting for about half of world production. The New Zealand King Salmon Company, dominates the production of king salmon in New Zealand. The company has its own selective breeding programmes integrated with quality control and production. Other salmon producers rely on stock from hatcheries where selective breeding is less well developed.