August 22, 2008
Trout Fishermen Fear Effect of Weed Attack
By CARPINTER, Bernard
BIOSECURITY NEW ZEALAND is preparing to use poison and carp to fight a devastating lake weed.
It plans to start on Lake Tutira, north of Napier, but fishermen are worried that the campaign could spoil the trout fishery on the lake and associated streams.
The weed hydrilla has been found in Tutira and three other small lakes nearby. Hydrilla crowds out native plants and forms dense mats.
"If it spread to some of our iconic lakes like Taupo or Waikaremoana the impact would be devastating in economic, social and cultural terms," Biosecurity senior adviser Victoria Lamb said yesterday.
"It's widespread in the United States and it costs them billions of dollars a year to clean it up."
The first step, if Biosecurity receives clearance from the Conservation Department, will be to spread the poison Aquathol K in Tutira. That would kill the hydrilla and some other weeds, Ms Lamb said.
Step two would be the release of grass carp, which would eat remaining hydrilla and other plants.
It would be the first time this approach had been used to control hydrilla in New Zealand.
Ms Lamb said the poison should not affect native plants but the carp could force trout to change their diet to some extent.
Biosecurity was now beginning a consultation process and hoped to be able to start its programme in spring, she said.
Napier fisherman Derek Williams said Tutira was one of the most important trout fisheries in Hawke's Bay, and anglers feared the Biosecurity plan would reduce trout numbers. Eliminating weeds would drastically reduce the number of insects available for the trout to feed on.
Hawke's Bay Regional Council biosecurity manager Campbell Leckie said hydrilla was a serious threat.
"We've got to do something."
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