Sunburn killing whitebait - study
Whitebait are getting fried before they hit the pan, with sunburn killing millions of their eggs, new research shows.
Canterbury University researchers, in a study released today, found that whitebait production was massively reduced because of sun damage to eggs.
"If they don't have a protective canopy above them, they're going to get fried," said Dr Mike Hickford, of the university's marine ecology research group.
He said the main species of whitebait, inanga, spawned almost exclusively under riverbank vegetation in tidal areas where fresh met salty water.
The eggs were laid in spring tides in late summer to early autumn, and developed out of water for weeks, which was unusual for a fish species.
Once the eggs were ready to hatch, which averaged about four weeks, the next spring tide would cover them and they would hatch and then be washed out to sea.
Hickford said riverbank modifications and livestock grazing had damaged vegetation, affecting breeding grounds.
Lower vegetation meant less shade for the eggs.
About half of whitebait eggs died in good habitat but that increased to a 95 per cent in poor habitat, Hickford said.
Even slight increases in temperature and radiation exposure had a major impact.
He said while whitebait numbers were unknown, anecdotally it seemed that catches were declining, but that could be because of better fishing techniques and more people fishing for whitebait.
Hickford's research into whitebait habitat will be part of the country's biggest-ever whitebait exhibition, which will open at the Hokitika Museum on September 9.
Museum director Julia Bradshaw said a theme of the exhibition was the belief whitebait catches had declined since the 1970s.
"There were some fantastic hauls in the early days. The record for one person in one day is 113 kerosene tins, caught by Des Nolan on the Waiatoto River during the 1940s. That's around 2000 kilograms of whitebait," she said.
"Without refrigeration or access to canning factories, there was often simply too much whitebait and it was used as chook feed and garden fertiliser."
Today marks the start of West Coast's whitebait season, which is 2 1/2 weeks later than the rest of New Zealand.