Whitebait research breeds possibilities

A Raglan-based fisheries consultant has become the first New Zealander to breed whitebait in captivity, and his research may also help solve the problem of what to do with waste effluent from farms.

Since 1997, Charles Mitchell has invested thousands of dollars of time and his own money in researching the aquaculture of whitebait.

Over 50,000 adult whitebait (inanga) brood stock were spawned repeatedly between May and October in 2005 at his "laboratory" of six ponds, resulting in some 250 million whitebait larvae being released into Raglan Harbour from June until September.

"We can reliably breed them in bulk with low labour inputs and enough whitebait return to the ponds each year from fresh hatched larval releases to provide a population growing at around 25 per cent per annum," he said. "But the big barrier to a commercially viable whitebait industry is the very high natural mortality rate of larvae."

Mr Mitchell said that in the wild fishery, over 99.5 per cent of whitebait larvae died between hatching and returning from the sea.

Research at Raglan suggests that both improving harbour water quality and increasing the amount of feed available in the first few weeks of life is critical to boosting whitebait survival rates and ultimately catch levels.

Mr Mitchell has experimented with a variety of organic waste products as food for zooplankton, on which baby whitebait feed. Better fed zooplankton result in bigger whitebait quicker, increasing survival chances.

At the same time, he said, his research could offer the agriculture industry new ways to manage polluting effluent.

- NZPA