Is NZ becoming a tropical holiday destination for fish?

It’s been a year of unusual fish species turning up in New Zealand’s coastal water – some of them tropical visitors.

After jellyfish swarms in Wellington and kingfish making their way down to Dunedin over summer, a 2m Queensland groper turned up last week off Northland.

Niwa fisheries scientist Malcolm Francis says Queensland groper have been spotted only a dozen times in 30 years in New Zealand waters.

They can grow to 3m and 500-600kg, he says.

It’s not clear what brought the groper to the HMNZS Canterbury wreck in the Bay of Islands – but Francis says they’re known to wander, and do turn up in places where it’s probably a little bit cold for them.
They head off on spawning migrations at certain times of the year, there are very few in New Zealand, so it’s unlikely to be spawning here, he says

Niwa has been tracking tropical visitors for the past 30 years.

Francis says every time there’s a warm summer, larvae of tropical and subtropical reef fish wash down from Norfolk Island and Lord Howe Island, and land on offshore islands around Northland such as the Poor Knights Islands.

“If they survive the winter they may grow up and add to the biodiversity of our reef.”

So far numbers are small but if global warming increases more and more will turn up and eventually breed, he says.

Tuna, marlin, tropical sharks and other oceanic species swim here when the water is warm and head back north in winter.

Water temperatures around New Zealand were 2-4°C higher than normal over summer, so kingfish, normally found in the north, extended their range as far south as Dunedin.

Jellyfish swarming into Wellington harbours may have been because of sea warming, but Francis says it could equally have been the different weather conditions allowing the m to breed or just drift closer than usual to shore.