The Atlantic Canada Fish Farmers Association is asking Environment Canada to launch a second study on lobster exposure to deltamethrin in the Bay of Fundy.
The chemical is the active ingredient in the pesticide Alphamax, which had been approved for use for a limited time on fish farms in New Brunswick.
Earlier this week the federal department shut down use of the pesticide in open fish farm cages after some lobsters died on the first day of a trial.
Environment Canada officials carried out their own study in which they released lobsters in a tarped cage undergoing pesticide treatment, then towed the lobsters through the water as the pesticide dissipated.
Some lobsters died in the trial, and as a result the federal department halted the use of Alphamax treatments in open water.
Pamela Parker, the executive director of the Atlantic Canada Fish Farmers Association, said the test scenario they put the lobsters through isn't realistic.
"I was frankly shocked that they put lobster directly in the net pen, and not surprised they died," Parker said.
As well, Parker said, the lobsters weren't properly assessed for their health.
This development comes just days after groups from new Brunswick and Nova Scotia came together to form the Atlantic Coalition for Aquaculture Reform.
While the pesticide can no longer be used in the salmon cages, Environment Canada is still allowing Alphamax treatments of farmed fish to be done in contained areas called well boats.
Scientists with the provincial government have also been monitoring the tests and the use of the pesticide.
Matthew Abbott, a spokesman for the Fundy Baykeeper, an environmental organization, said he's concerned about the effects on smaller lobsters, considering the result of the testing.
"If large adult lobster are killed by this, one can imagine what it can do to lobster larvae," Abbott said.
The fish farmers association wants Environment Canada to try the experiment again by placing lobsters in a more realistic scenario, underneath and around the cages during treatment.
There's no word on whether the federal department might grant that request.