A salmon infected by sea lice. (Photo: GNU License)
Sea lice now resistant to chemicals
Tuesday, June 08, 2010, 17:10 (GMT + 9)
Sea lice in New Brunswick's (NB) salmon aquaculture farms were found to be resistant to emamectin benzoate last year. Sold as SLICE, this chemical was the industry's main way to tackle the pest since 2000.
"SLICE was super-effective and no other product was coming into the market," said Larry Hammell, director of the Centre for Aquatic Health Sciences at the Atlantic Veterinary College (AVC) in Charlottetown. "We need another product."
And the industry needs it before the warmer water lets the sea lice thrive in the floating cages in the Bay of Fundy this summer, he added, Telegraph-Journal reports.
Recently, at a closed meeting in St George, aquaculture representatives discussed "well-boat" treatment for the lice. This system entails the pumping of salmon into a large boat with a waterproof hold or tank where the fish are treated prior to returning them to their sea cages.
The New Brunswick Salmon Growers' Association anticipates a leased well-boat to arrive soon.
Salmon growers still require approval from Canada's Pest Management Regulatory Agency for the pharmaceuticals to be used in the well-boat. Executive Pamela Parker hopes to attain approval within two weeks to use the disinfectant hydrogen peroxide.
She hopes the agency will approve deltamethrin, sold as Alpha Max, by late summer. The agency approved this chemical last year for use in a very limited area of Passamaquoddy Bay.
Fish farmers also want the agency to approve azamethiphos, sold as Salmosan. Farmers are allowed to use it in sea cages only.
Hydrogen peroxide, Alpha Max and Salmosan kill sea lice in a "bath treatment" effective at killing the pest in its adult phase, Parker informed.
But the industry now needs an "in-feed" product that kills juvenile lice to replace SLICE until sea lice lose their resistance to it.
The remaining legal in-feed option is teflubenzuron, sold as Calicide, Parker said.
An effective integrated pest management system must include an arsenal of products, bath and in-feed, that is applied in a planned rotation to combat sea lice at different stages of their life cycle, Hammell explained.
Ian Gardner from the University of California Davis, named to the Canada Excellence Research Chair in Aquatic Epidemiology, will soon arrive at AVC, which is part of the University of Prince Edward Island.
Gardner will also visit salmon cages in St George, Hammell said.
In the Bay of Fundy, fish farmer’s pesticides must only kill sea lice. However, Environment Canada identified the agricultural pesticide cypermethrin on the shells of lobster there last fall.
Farmers in New Brunswick use cypermethrin to kill potato bugs.
The salmon growers association asserts that its members would not use cypermethrin even though it does kill sea lice. Environment Canada is running a continuing criminal investigation into how this chemical entered the bay.
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By Natalia Real