Five of 12 juvenile ururoa/great white sharks caught by recreational fishers in the past year have been in Northland, causing concern among shark scientists, particularly about the use of torpedoes to set long lines.
The Department of Conservation is alarmed over number of juvenile white sharks caught on fishing lines, particularly in Northland.
DoC said 12 juvenile white shark captures have been recorded since March last year around the upper North Island.
DoC's shark expert Clinton Duffy said five of the captures were recorded on Ninety Mile beach, with the most recent capture last week.
"The number of juveniles being caught on fishing lines is a concern because these sharks are endangered, and it means they won't grow to maturity and contribute to the breeding population," Duffy said.
Recreational fishers using kontiki and "torpedoes" to set longlines off beaches were responsible for at least seven of the shark fatalities recorded.
"We want fishers to understand that white sharks are protected and should be released in the water immediately. They shouldn't be hauled up the beach or dragged backwards by their tails because that will cause further injury," he said.
There are estimated to be only around 750 adult great white sharks in New Zealand and eastern Australian waters. They are vulnerable to a variety of fishing methods, including trawls, set nets and longlines and have even been found drowned in crayfish pots.
In several instances the sharks were quickly released and probably survived capture. In other cases the carcasses were found discarded on beaches, in some cases they had been butchered or had their jaws removed, and one carcass was finned before DoC staff were able to recover it.
While it is not illegal to accidentally catch or even kill a great white shark all fishers are required to release it immediately and report the event to DoC or a fisheries officer as soon as possible.
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It is illegal to retain any part of the shark for food or as a memento or trophy, even if it is dead.
People should report sightings of great white sharks to 0800 DOC HOT (0800 36 42 68) or send a photo to the sharks mailbox: firstname.lastname@example.org
Reporting sightings (recent or historical) assists research on the species, particularly understanding when and where they occur in different parts of the country.
GREAT WHITE FACTS:
■ White sharks, often called white pointers or great white sharks, are large, iconic marine predators.
■ New Zealand is a global hotspot, along with California, South Africa, Australia and Japan.
■ They have been protected in NZ waters since April 2007.
■ Juveniles and adults occur in shallow coastal waters, including large harbours and estuaries.
■ Sub-adults and adults also occur in the open ocean, as well as around offshore islands and banks.
■ Tagging studies show movement of great whites between NZ, Australia and the southwest Pacific and South Africa.
■ Satellite tagging of NZ white sharks has shown juveniles and adults migrate seasonally, from March to September, between aggregation sites at Stewart Island and the Chatham Islands to the tropical and subtropical Pacific.
■ These sharks appear to spend at least 5-7 months north of NZ before returning, often to the exact place where they were tagged.
■ White sharks are apex predators and may play an important role in controlling the populations of important prey species. Although they may be encountered anywhere within New Zealand's Exclusive Economic Zone, they are most frequently observed in areas close to large seal colonies.
■ Males are estimated to reach maturity at 3.5-4.1m total length and females between 4.2-5.2m. Size at birth is 109-165cm total length and 20-30kg weight. Litter size is between 3-14 pups but usually fewer than 10. The gestation period is unknown but is estimated to be about 18 months.