THE GLOBAL WARNING

As seas around New Zealand heat at an unparalleled rate, scientists are starting to understand what it might mean for marine ecosystems around the world

- Tess McClure

IN THE SHALLOWS OF ARAMOANA, FISH ROILED THE SURFACE OF THE BAY, flickering through the water, reflecting the winter sunlight. Some floated belly up, stunned and dying. Others spun in tight circles. In shallow pools created by the eddying tide, they lay piled on their sides. Occasionally a fish would raise a single fin, worrying the water's edge. Peter Langlands waded in, grabbing live fish one by one. He had long been an active fisher on the coastlines of New Zealand's South Island, and knew they were ray's bream: good eating. Later, he would fillet them, and cook the firm white flesh with spices for a curry. Even as he thought ahead to the evening meal, though, Langlands felt a pang of worry.

The fish had been beaching for months - masses of them, through April, May, June, July. Entire schools died flapping in the Otago bays, their scales a dark, briny silver - an offshore fish, meant for deeper, colder waters. Locals posted videos of them surging over the sandbanks or laid out in their hundreds on the sand; of toddlers striding through the shallows to yank one out by the tail.

In 30 years of fishing, and writing for the local fishing magazine, Langlands had never seen anything like it.

Fish strandings are by no means unheard of - schools get chased in by predators, carried by storms, caught by the shallow sandbars of a bay. "Generally when that happens, though, you're talking about individual fish - not thousands and thousands over a six-month period," says Langlands. "I've never heard of anything happening on this scale before in New Zealand."