Eel Farming in Waikato

December 2015

The work of fisheries biologist Charles Mitchell to make use of nutrient run-off from farms

Fisheries biologist Charles Mitchell has developed a system for farming eels on his block of land near Raglan utilising farm nitrate runoff.

Charles has been involved in research on New Zealand freshwater fisheries since the 1970’s.  He worked with MAF in their Fisheries Research Division including work on field trials of Chinese grass carp and also designed and built fish passes for native fish and eels.

Charles also worked on the first hatchery for the commercial scale breeding of Malaysian Freshwater Prawns.

Charles bought a property at Te Uku near Raglan in 1994. The property overlooks the Waitetuna River where it meets the harbour. He started to convert the land into a fish farm, treating the block as a large experiment.

His first focus was whitebait. He says by draining the Waikato’s wetlands for farming whitebait, breeding grounds had been ruined. Charles provided habitat along protected pond banks and watched the numbers of whitebait increase. Over more than ten years he says he proved he could farm whitebait and his restoration work has improved the whitebait population in the area.

It’s estimated that the value of the commercial eel industry in New Zealand is around $17m. Almost all commercially harvested eel is exported, traditionally to Belgium, Germany, UK and the Netherlands. In recent years Korea has become a major market. In New Zealand there are two main types of eel – longfin and shortfin.

The commercial fishery for eels got underway in New Zealand in the 1960’s. Eels have been in the quota management system since 2000 in the South Island and 2004 in the North Island.

The literature on the eel fishery suggests that dams have a big impact on migration of eel populations. What data exists on eel numbers suggests that eel populations are in decline.

In 2007/2008, the quota for North Island longfin eels was reduced by over 50% in response to concern on declining numbers.

The goal of Charles’ company was to develop a sustainable fishery while achieving nitrogen and e-coli mitigation for farms and other land use.  He is achieving that goal by harvesting juvenile fish – whitebait, eels and mullet – which are attracted to his system’s plankton rich discharges and then growing them to adulthood. The farm design replicates wetland ecosystems and is set up for whitebait spawning and eel rearing.

Charles says his whole system is built on natural ecology and relies on tides. There are manual sluices that he’s built himself, which allow fish to enter a holding pond before being transferred to the farm.

Charles says in spring large numbers of little eels arrive on the coast and head up rivers looking for somewhere to live. Most of those eels will die from predators, disease and lack of habitat. He has set up ponds creating an eel friendly habitat for eels to settle. He says eels in his pond can grow much faster than eels in the wild. Once the eels are ready to migrate again, they are caught and then held in ponds.

Raglan Eels Ltd., the research company founded by Charlie Young, is capable of producing ready for market eels that they believe are superior in quality to wild caught eels.

Currently the company is taking part in a research project with NIWA to investigate dairy farm waste use in growing micro-algae that can feed larger invertebrates that can then be used to feed eels or whitebait.

Aside from the eel research, Raglan Eels Ltd also does fisheries consultation and marine science education. The farm and research base regularly host tours and school groups.