Whitebait Farming Research

Researchers at Mahurangi Technical Institute say they have made a significant breakthrough in the commercial farming of whitebait by discovering the method of breeding of the giant kokopu – one of the five native fish we collectively call whitebait.

Whitebait are the young of some of New Zealand’s native fish. Some of the species you are likely to catch in your whitebait net are inanga, kōaro, banded kōkopu, giant kōkopu and shortjaw kōkopu,. These are‘true’ whitebait.

They belong to the Galaxiidae family,.Although galaxiid species are found in many places in the Southern Hemisphere, the giant, shortjaw and banded kōkopu only exist in New Zealand. Our galaxiids are generally nocturnal and very good at hiding. They love bushy streams, where they find both shelter and food, with a rain of insects falling from the overhanging plants.

Eggs are laid in estuary vegetation around the high-water mark on a very high tide (known as a spring tide). Males fertilise these. Most adults die after spawning. The eggs are exposed for a number of weeks, but remain moist among the vegetation.

When another spring tide reaches the eggs, the larvae hatch. Then the falling tide carries them out to sea, where the hatchlings spend the winter, feeding on small crustaceans.

Juveniles – and now we are talking whitebait – make their way upriver to live in freshwater habitats. By autumn the mature fish are ready to swim back downriver to spawn in the estuaries.

Whitebait are in decline. Mostly, this is due to a lack of clean, healthy rivers and streams for the adult fish. Barriers, such as dams and overhanging culverts, also block migrating whitebait from reaching what clean streams remain. Introduced fish compete for habitat and prey on our native species. Introduced plants clog up the places where whitebait live.

Planting and fencing stream edges can lead to better whitebaiting in future years. The adults love bush-covered streams and the young whitebait are attracted to the streams where adults live. Fencing waterways stops stock from trampling the plants and banks where fish take cover, and from crushing whitebait eggs. Dams and overhanging culverts can also be altered or removed to allow young whitebait to reach the adult habitat, increasing the number that develop to breeding age. More adult galaxiids means more whitebait in the future.

Whitebait are one of a handful of native species that can be legally harvested and sold. In 2006 there were no limits on the amount of whitebait anyone could take as long as they were fishing legally. Fishing is controlled by the Department of Conservation and regulations vary, with hand-held nets allowed in some areas and fixed nets in others.

While they may not be the first to have cracked the method of breeding the giant kokopu, researchers at Mahurangi Technical Institute have managed it on a large scale.

They don’t believe their breeding programme will bring an end to fishing in the wild, but they do see it as a serious business opportunity, which will also take some pressure off the wild population.

Mahurangi specialises in the development of freshwater fish breeding techniques for commercial and conservation purposes.

The project with the giant kokopu breeding has taken five years of research and trials.

While kokopu are only one of the fish species that make up whitebait, they are the tastiest. That makes the success of breeding them as a commercial stock so appealing.

There are two other kokopu species in the mix – banded and shortjaw, along with inanga and koaro. The giant kokopu fish are the longest-lived of the whitebait species at around 30 years. They don’t develop the strong fishy taste of the other shorter-lived species until much later.

Understanding how the fish breed in the wild was a big part of their success. That will also make it easier to supply the eggs to prospective fish farmers.

The eggs’ peculiarities make it easy to supply them to prospective farmers as they won’t need to be shipped in water.

Farmers will be able to order their eggs and 10 weeks later have whitebait to sell, says Paul Decker. Three fish farmers are already interested, he adds.

Questions on farming have been raised by others in the wake of this breeding breakthrough such as how do you feed farmed fish (generally the meal and oils come from farmed fish stock). Conservationists also argue that fish farming will take away any responsibility of looking after the wild stock but Paul Decker says the conservation of freshwater native fish is at the heart of the institute’s aquaculture department research. He says that the laying of its eggs in grass helps to explain the decline of the giant kokopu, and why fencing stock from and cleaning up waterways is important.

Once a population has gone from a stream, young fish won’t repopulate on their own, they need the scent of an established population in the stream before they will venture up it.