One fish, two fish, pest fish, shoo fish

university-of-waikato

Tue May 26 2009 12:00:00 GMT+1200 (New Zealand Standard Time)

One fish, two fish, pest fish, shoo fish

Tuesday, 26 May 2009, 10:37 am
Press Release: University of Waikato

Media Release
May 26, 2009

The Waikato basin is “pest fish central”, with the invasive koi carp making up nearly 80% of the biomass of the fish living here, 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.

Their work features at the university’s stand at the June 10-13 Fieldays at Mystery Creek near Hamilton. The University of Waikato is again a strategic partner at Fieldays.

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 our bodies of water should look.

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.

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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.”

Dr Hicks says pest fish such as koi carp, rudd, catfish and feral goldfish are thought to be responsible for the cycling of nutrients (from the runoff of nitrates into the water) which causes increased algal blooms. “Many farmers use these bodies of water on their land for water supplies. But those blooms produce toxins and there have been reported cases of stock death, so it’s a big issue for farmers.”

And he says it’s important that farmers distinguish between grass carp and koi carp. “Grass carp, which don’t breed naturally in the Waikato as far as we know, were introduced in selected areas to control aquatic plants, and they have a place in our ecosystem as long as they are contained. However, some farmers have been told koi carp will do the same thing, but of course they breed out of control and clog and degrade their water, turning their lakes and farm dams into a muddy mess.”

Although koi carp were recognised as a pest fish in New Zealand in the 1970s, little work was done on their environmental impact – until Waikato University scientists started picking up on the issue about 10 years ago.

Dr Hicks says that work, by scientists and masters and doctoral students, aims to establish the impact of pest fish on the environment, and figure out the best way to control them once it’s known exactly what harm they cause. He says it’s the sensible approach, rather than simply embarking upon eradication programmes which would cost millions of dollars.

Freshwater restoration and pest fish control are just two parts of a huge, $10 million, 10-year research project led by Waikato University and funded by the Foundation for Research, Science and Technology to clean up lakes and improve their biodiversity. Waikato University is working with the likes of Department of Conservation, Environment Waikato and Environment BOP, Niwa, Fish and Game and community groups on the project.

As part of the project, the university researchers use an electrofishing boat (the only one of its kind in New Zealand) which temporarily stuns the fish so they can be caught for surveys. A PhD student has also been using remote sensing to track the movement of pest fish.

Next, the Waikato team plans to remove pest fish from five selected water bodies in the Waikato region and monitor their ecological systems to establish what damage the fish are doing. The lakes are being selected now; work on clearing them should begin within the next year, and continue for up to three years.

. Dr Hicks speaks about pest fish at 12noon on Friday June 12 during the Waikato University Seminar Series at Fieldays. Topics by other Waikato University speakers over the four days include nitrogen pollution in waterways, restoration of native bush and wetlands and learning in cows.

ends

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