Health Canada has granted New Brunswick's request to allow the province's aquaculture industry to use a restricted pesticide to fight sea lice infesting farmed Atlantic salmon.

The federal organization is allowing the emergency use of Alphamax — a pesticide whose main chemical ingredient is deltamethrin — on farmed salmon between October and December of this year.

The industry plans to start using the pesticide in the Bay of Fundy later this week on farmed fish that have been plagued by sea lice — parasites that attach to and feed on salmon.

Treatments of Alphamax will be restricted to tarped cages or contained areas called well boats, which are boats with large holds. The fish will be placed in the boats, bathed in a concentration of Alphamax and released back into the cages, along with the treated water.

Nell Halse, of the Atlantic Canada Fish Farmers Association, said, ideally, the industry wants to be able to use a rotation of chemicals so the sea lice don't develop a tolerance to any one particular substance.

"That whole process, from our farmers' point of view, takes too long," she told CBC News. "We needed these treatments, a whole suite of them, in the spring when sea lice first started showing up on our farms.

"If we'd had three to four different treatments that we could rotate around to deal with the different stages of sea lice, we would've been in good shape last spring."

Instead, Halse said, the industry has been struggling to contain an unusually bad sea lice problem because of the high ocean temperatures in the summer. She said the approval of the use of Alphamax came after a lengthy risk assessment.

Matthew Abbott, a member of the Fundy Baykeeper Project, said the sea lice troubles are of the industry's own making and linked to its long-term use of pesticides.

He said putting more chemicals in the water is not the right solution.

"I think it goes to show that the problem isn't being solved," he told CBC News. "Instead of funding sustainable practices that don't lead to these massive sea lice outbreaks, they just keep adding new chemicals."

There is also concern that deltamethrin, which targets crustaceans, will kill lobsters and other creatures along with the sea lice.