ST. JOHN'S, N.L. -- A prominent conservation group is calling on Newfoundland and Labrador to restart the environmental assessment for a planned aquaculture expansion after more than 2 million salmon recently died in the same company's pens.

Northern Harvest Sea Farms, owned by the Norwegian company Mowi, plans to expand a salmon hatchery in Stephenville, in western Newfoundland.

Steve Sutton with the Atlantic Salmon Federation says that the initial assessment did not study what happens when the hatched salmon are transferred to the company's existing sea cages.

He told a news conference today those cages include facilities on the island's south coast, where 2.6 million fish died last month, deaths the company attributed to a long period of high water temperatures.

Sutton says provincial Environment Minister Derrick Bragg should restart the environmental assessment before the matter goes to court next month in a challenge brought by conservation groups.

Northern Harvest and its open-net aquaculture practices have been scrutinized over the past month as images of salmon residue being dumped into the ocean have surfaced during the dead fish cleanup.