Whitebait Farming in New Zealand

An interview with research scientist, Charles Mitchell, who has managed and built up whitebait populations and is now turning to marine polyculture.

“After working with Ag & Fish managing other fisheries until 1985, I went back to whitebait management and studied the spawning grounds. The basic hypothesis of the limiting factor was that it was known that whitebait laid their eggs out of water along stream banks where cattle often grazed, trampling the eggs and destroying whitebait runs. I wasn’t sure this explained the problem although major programmes were undertaken to fence off and protect streams from cattle damage.”

As a fisheries scientist, Charles’ real job was to make a positive contribution by figuring out why whitebait numbers declined. He moved to Te Uku, in New Zealand’s Waikato region, 20 years ago and bought virtually useless swampland as part of a larger property.

Charles Mitchell’s whitebait and Eel polyculture marine farm in Waikato – Photo Theresa Sjoquist

Farming Whitebait

“I thought the best way to learn about whitebait was to see if you could build up a population by optimizing their survival, growth and egg production, by using aquaculture methods. I undertook seven years of research to identify spawning grounds around the country from the West Coast to Northland, Waikato to Mokau and Bay of Plenty, trying to determine what factors affected the survival of whitebait eggs. I followed the spawning, reasoning that you could manage the fishery if you could take a population and observe them. The issue wasn’t necessarily the eggs.”

Charles decided to buy the land and put his money where his mouth was as an independent researcher, and see if he could manage a captive whitebait population. Over the past ten years he’s done just that, building the numbers up and increasing the number coming back to their stream over 5 years by 100 times.

Successful Whitebait Management

“I was steered by good fortune towards significant meticulously kept historical local records. One was Carlin Corbet’s daily catch at the same spot on the Waitatuna River over 28 years, and the other was Neil Gavin’s rainfall records from Te Uku since 1936. When I analysed these two sets of data, it became obvious that there was a strong relationship between the numbers of whitebait coming back to the Waitatuna River each spring and how much rain we’d had in May and June. I could predict with 77% accuracy the size of the whitebait run based on the rainfall.

“In heavy rainfall there was a poor run, and in a dry May and June, there were good runs. The El Nino and La Nina weather patterns also affected the runs. When it rains, the harbour fills up with dirty water comprised of a lot of fresh water, which meant 7mm babies became covered in colonies of bacteria and all the plankton in the harbor got washed out by a huge pulse of fresh water.”

Funding Shortage Leads to Whitebait Abandonment

Unfortunately, Charles was unable to find the funding support to continue the research so he stopped feeding the whitebait and has begun instead to feed eels and research the possibilities for fattening them.

Charles checking the lock for eels – Photo Theresa Sjoquist

Major World Market for Farmed Eels

“There’s a huge developing market in export for eels. 7% of the world’s fish meal production goes into the sustenance of eels. They’re very high in omega 3, and Maori relied on them in early years. Over the last five years, whitebait numbers have dropped back to their original population before I was managing them. They don’t grow as big or produce as many eggs.”

Marine Polyculture Farm

“I’m now managing the whitebait farm as a polyculture — in three levels, mullet, eels and whitebait. The whole system is built on natural ecology and relies on tides, and manual sluices built to my own design, which allow fish to enter a holding pond before being transferred through into the safety of the farm.”

As part of a bio-engineering project, Charles and his partners under the Ngai Tahu umbrella, quickly succeeded in ridding Lake Forsyth of a poisonous algal bloom which had baffled scientific specialists for decades.

Farmed eel – Photo Theresa Sjoquist

Turning Effluent into Whitebait Food

Charles currently has a small research grant from Environment Bay of Plenty to turn effluent into whitebait food.

“Oh, yes, it can be done,” he says. “We have the potential to grow huge crops of whitebait and eels if it’s engineered properly. Bio-engineering is engineering the environment utilising nature’s own resources — much the same as permaculture principles but on a much larger scale.”

“Most scientists are reductionists. I’m a synergist – I like to build something and I’m very focused on the results. We need creative solutions to grow a sustainable economy, not just short term, accountant controlled ‘low risk research.

Sources –Theresa Sjoquist Interview with Charles Mitchel – April 2011.

©Theresa Sjoquist