Farmed Atlantic salmon have been plagued by an unusually bad sea lice problem. (CBC)New Brunswick fisherman who rely on the ocean rather than fish farms for their livelihood are concerned about the effect Health Canada's short-term approval of a restricted pesticide for farmed Atlantic salmon will have on sea water and their catch.

The agency is allowing the emergency use of Alphamax on farmed salmon infested with sea lice — parasites that attach to and feed on salmon.

The use of Alphamax has been approved between October and December of this year.

The active ingredient in Alphamax is a chemical called deltamethrin. Health Canada says the chemical does not pose a risk to human health or the environment when it's used according to the label directions and under the federal agency's conditions.

Melanie Sonnenberg, a spokeswoman for the Grand Manan Fishermen's Association, said that explanation is not sufficient.

She said she wants more information about the specific conditions of using the pesticide, including how much of the product is allowed to be used and how often.

"It is like being in the dark, and it's difficult at best to get information," Sonnenberg told CBC News.

"There's no place for us; it's just a tug of war all the time."

Treatments of Alphamax will be restricted to tarped cages or contained areas called well boats, which are boats with large holds.

The farmed fish will be placed in the boats, bathed in a concentration of Alphamax, then released back into their cages, along with the treated water.

"We're talking about an industry, a fishing industry that relies on the water as much as the aquaculture," Sonnenberg said.

"We realize that everybody has to do their work, but we just don't feel that it can be … one industry at the expense of another. We want to make sure safeguards are put in place and that our industry is protected."

Pamela Parker, the executive director of the Atlantic Canada Fish Farmers Association, said trial research done on Alphamax last year showed no negative impact on lobster and no contamination of the sea.

She said more variety in pest control measures doesn't necessarily mean more chemicals will be used over time.

"In fact, we will actually use less product because we will be using it strategically, and we will be using the right product on the right life stage," Parker said.

"So, ultimately, we expect the use of chemicals will be reduced."

A spokesperson with the provincial Department of Fisheries said officials will release more details about Alphamax treatments on farmed salmon once they speak with stakeholders, including lobster fishermen.

The salmon farmers plan to start using the pesticide in the Bay of Fundy later this week.