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Invasive Koi Carp Overrunning Waikato Basin

by 5m Editor
26 May 2009, at 1:00am

WAIKATO, NEW ZEALAND - The Waikato basin is pest fish central, with the invasive koi carp making up nearly 80 per cent of the biomass of the fish living in New Zealand, say University of Waikato researchers.

“That’s vast,” says Associate Professor Brendan Hicks. “But we have no real recognition yet of what ecological impact they are having here or in the rest of the country.”

Dr Hicks and three other Waikato University Biology Department researchers are working on massive freshwater restoration projects which will eventually shape the way New Zealand deals with pest fish.

The university has embraced this year’s theme of My Land, Our Environment in its stand which will contain native bush, a model cow and two tanks of fish – one a murky melee of several varieties of pest fish, the other with clean water and native fish, representing how bodies of water should look in New Zealand.

Koi carp and feral goldfish will be among those used in the 1.2m by 0.7m tanks which contain half a tonne of water. They represent some of the pest fish in our waterways, while whitebait species inanga and banded kokopu will sit alongside them, as an example of how the nation’s waters would have looked 100 years ago.

Senior lecturer in biology, Dr Nick Ling, is in charge of getting the fish to the Fieldays stand. He says pest fish are fairly tolerant of harsh conditions so a week in the tanks won’t faze the fish which will be returned to the university for research work following the event.

He says it’s a great way to show people - particularly farmers - what pest fish are doing to their bodies of water. “In some areas there’s the equivalent of up to four tonnes of koi carp per hectare.”

Grass carp, which don’t breed naturally in the Waikato, were introduced in selected areas to control aquatic plants. However, some farmers have been told koi carp will do the same thing, but they breed out of control and clog and degrade their water, turning their lakes and farm dams into a muddy mess.

5m Editor