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Published: 2004-07-15 00:00:00

Environment Waikato has a 10 year plan to limit the spread of pest fish koi carp and brown bullhead catfish through the Region.

The fish pose a significant threat to the country’s freshwater ecosystems, and koi are classified as an unwanted organism under the Biosecurity Act. Environment Waikato has been working to better understand their biology and investigate control and management options, including part funding a Master’s Thesis, assisting a staff member to visit Australian agencies to explore practical management methods and investigating eradication methods of various fish populations throughout the Region.

The Council has also begun an interagency group and is working with DoC to establish pest fish signs around Taupo. It is investigating a joint agency database to record information and help establish the distribution of various species by recording sightings. The Council is also considering priority options for research.

DoC is preparing a National Pest Fish strategy to look at action and management nationally and a Waikato Pest Fish Research Strategy is also being prepared to deal with pest fish in this area.

Environmental officer Johlene Kelly said biological, physiological and habitual information on koi carp was limited and many projects were underway to fill the information gaps at universities and DoC.

DoC research includes input into the daughterless carp genetic technology programme in Australia which ‘switches off’ the genes which make fish female, progressively making the fish more male. Eventually the entire population becomes male and dies out through lack of reproduction.

Other DoC projects include investigations into the use of potassium permanganate, an antidote to Rotenone, the chemical which kills carp, and trials are underway on the most effective way to clean nets to avoid spreading the eggs. She said tools for successfully eradicating koi carp were very limited.

The short-term, three year plan included expanding education and advocacy on pest fish issues throughout the Region, a monitoring and surveillance programme in conjunction with DoC and implementing eradication mechanisms in high priority sites.

The longer term, 10-year plan had a goal of limiting the spread of pest fish. It included reassessment of new and potential fish species for the next Regional Pest Management Strategy, close interagency links, increasing awareness of the threat of pest fish and stronger involvement with Australian agencies.

Cr Evan Penny said he supported practical trials, as the plans did not include much action.

“Pest fish are a biodiversity as well as a biosecurity problem, and more can often be achieved with a couple of weeks dabbling in the field than all the strategies in the world.”