Tropical fish hightailing it to New Zealand waters

An invasion of tropical fish previously unseen in New Zealand waters could be an effect of global warming, a marine expert says.

Eyestripe surgeon fish, yellow boxfish, black-spot goatfish, two-tone wrasse and an unknown species of damselfish have been found by divers off the east coast of Northland this month.

Marine expert Wade Doak says they're an indicator of climate change. "They come down in larval form from places like Lord Howe Island and the Kermadecs and spend the long voyage in a suspended state."

Doak said the fish travelled as far as islands in the Bay of Plenty but didn't survive long enough to breed. As waters became warmer though, "sooner or later they'll find it acceptable".

He said the new arrivals were welcome but the implication of global warming was that sea levels were rising.

"We have to take this on board and decide whether to invest in beach property."

Niwa principal scientist James Renwick said the rise in sea temperatures was more to do with a strong La Nina weather pattern than global warming, although that was playing a part.

Fish were sensitive to sea temperatures and even a 1C change could shift stocks a long distance.

Fishing expert Geoff Thomas suspected many tropical species had been in New Zealand for some time.

"It's just that people haven't seen them before," he said.

But Doak said if it wasn't for divers, scientists wouldn't know what fish were here.

"If they've been there all along I'll eat my mask."