2.6m shark from tropics found off Nelson

Marine experts are waiting to see if one of the most deadly species of shark has found its way into New Zealand waters after a surprise catch off the South Island.

A 2.6m-long shark was caught in a fishing trip off D'Urville Island, about 50km north-east of Nelson. A local aquarium owner suspected it was a bull shark, but it is now being frozen and sent to Te Papa Museum for confirmation.

If it is a bull shark, it will be the first found in New Zealand waters. It usually exists only in more tropical seas. Bull sharks are believed to have killed 21-year-old Sarah Kate Whiley off a Queensland island earlier this month.

"It is considered by some people to be the world's most dangerous shark species in terms of attacks on people," said Te Papa fisheries collections manager Andrew Stewart.

"They are a very powerful fish. Their teeth and their jaws are just like a great white's. They are triangular, they are serrated. It tends to stick quite close to shore. It grows quite large, nearly 3.5m total length, and it's most notable for the fact it can and does penetrate a long way into fresh water."

Mr Stewart had viewed pictures of the shark caught near D'Urville Island and recognised it as from the whaler species but could not be sure it was a bull shark until analysing tooth shape and fin size.

"Assuming it is a bull shark, the next question you have to ask is: Is this a one-off straggler? What would be a concern is if, suddenly, we start seeing numbers of bull sharks up the Waikato River, for instance.

"But one bull shark does not a plague of sharks make. I have seen individual species of fish turning up as solitary specimens hundreds of kilometres outside of their known range. It doesn't mean they ever establish."

Mr Stewart said the shark was unfairly maligned and misunderstood.

"Sharks are the stuff of nightmares. We demonise them. But when we go to try to keep them in aquariums and study them, they are suddenly very fragile, they die. What we don't know about sharks could fill libraries," he said.

Shark attacks are a rare occurrence.

"Quite frankly, you are in much greater danger getting in your car and driving off down the road. Yet we don't think twice about that. Sharks are in much greater danger from humans than the other way around."