New Zealand’s shark fishery
In New Zealand sharks are eaten in fish and chips – the fillets are in high demand because they are tasty and free of bones. Exports of shark products, which include fins, liver oil and cartilage, increased rapidly between 1988 and 1991, and since then have fluctuated from 3,000 to 6,000 tonnes per year. Korea, Australia and Japan buy most of New Zealand’s shark products, with smaller quantities going to France, the United Kingdom and the United States. Korea buys spiny dogfish, Australia school and rig sharks, and Japan chimaeras (ghost sharks).
Not all the sharks which are caught have been targeted by the fishing industry; sometimes they are by-catch from tuna fishing or bottom trawling.
Found around New Zealand and Norfolk Island, the abundant and harmless rig shark (Mustelus lenticulatus) is 1.5 metres long, and grey or bronze with spots and a white underbelly. They take their food from the sea floor, no deeper than 860 metres, preying on crustaceans, especially crabs. Like many sharks, they do not lay eggs, but incubate them inside their body and give birth to developed young.
Rig sharks are the fish most often served up in fish and chips. They are caught mainly by set nets, and also by trawling. Reported landings peaked at 3,826 tonnes in 1983. In 2002–3 the annual catch limit was set at 2,034 tonnes, but recorded landings were only 1,449 tonnes. Casualties of rig fishing include Māui's and Hector's dolphins, which become trapped and drown in set nets.
Rig sharks are also known by the common names lemon fish, spotted dogfish and gummy sharks, and by the Māori names kapetā, mangō and pioke.
Probably the most abundant living shark, the spiny dogfish (Squalus acanthias) is a small species measuring just over 1 metre. The small spines on their dorsal fins can inflict a nasty wound. The fish are dark grey with white spots and a white underbelly. Spiny dogfish can live for at least 26 years in New Zealand, but populations in the Strait of Georgia, in Canada, can live up to 70 years. They hold the record for the longest gestation period of any animal – 24 months. Females mature at 10 years in New Zealand, and as late as 24 years elsewhere.
Although extensively fished for fish and chips, spiny dogfish have nevertheless increased, replacing species such as hoki or barracouta in areas where these have been overfished. Fishermen reported landing 11,530 tonnes of spiny dogfish in 2001–2.
The name dogfish was coined by anglers who observed them chasing smaller fish in large packs, like dogs. The sharks are also known as spinebacks, and by the Māori names koinga, kāraerae, mako-huarau, mangō-hapū and mangō-pekepeke.
School sharks (Galeorhinus galeus) grow to 1.7 metres in New Zealand, and 2 metres elsewhere. They have a life span of more than 50 years. They are grey on top and white underneath. Found worldwide in temperate waters, in New Zealand they are most common in the north. They inhabit both coastal waters and the open ocean, and are capable of swimming very long distances – 10% of all the tagged school sharks recaptured by scientists had swum 1,700 kilometres from New Zealand to southern Australia; one had travelled 4,940 kilometres.
In the early 1940s school and other sharks were harvested for the vitamin A in their liver oil, until the production of synthetic vitamins began in the 1950s. High mercury levels were detected in large school sharks, leading Australia to ban New Zealand imports temporarily in 1972.
In 2002–3, 3,151 tonnes of school sharks were caught, down from a peak of 4,776 tonnes in 1984, just before the introduction of a quota system. Because they are slow-breeding, school sharks are vulnerable to overfishing.
As their name suggests, these sharks frequently swim in schools. They are also known as grey sharks, and by the Māori names makohuarau, tupere and kapetā.
Chimaeras – also known as ratfish or ghost sharks – are the closest living relatives of sharks and rays, although they differ in a number of ways. They have large heads, bulging eyes, smooth skin without scales, and whip-like tails. Some chimaeras, such as the dark ghost shark (Hydrolagus novaezealandiae) and the elephant fish (Callorhincus milii), are fished commercially.
Using their trunk-like snouts to detect buried shellfish, elephant fish live in coastal waters and around the continental shelves of New Zealand and southern Australia, to depths of at least 200 metres. About 1.2 metres long, they are silvery white with a golden sheen, with dark patches on their backs.
Elephant fish are caught in commercial set nets or by trawling when they migrate into large estuaries and bays to breed in spring. In 2002–3 a total of 1,124 tonnes were landed, most of it trawled in fisheries off Banks Peninsula.
Elephant fish are also known by the Māori names makorepe and reperepe.