Sea lettuce is choking the Mill River, says Hal Perry, Opposition environment critic. (Ryan Hicks/CBC)

The provincial government needs to start harvesting sea lettuce in Mill River again, says the Opposition environment critic.

Hal Perry said sea lettuce is choking out oysters and costing fishermen their living.

The underwater plant grows profusely when there is excess nitrogen in the waterway from nitrate run-off from farmers' fields, industry, cities, sewage or forestry practices. As it rots, it sucks oxygen from the water.

But Environment Minister Janice Sherry said harvesting the abundant sea lettuce is not going to solve the problem.

"It's like shovelling snow in the middle of a snowstorm," she said. "You can pull all the sea lettuce that you want out of the rivers but if we don't address nutrient management on the land, it's almost an exercise in futility."

Oyster fisherman Johnny Powers said he's never seen an oyster season this bad.

"All dead, not a single living oyster amongst it," said Powers, as he pulled up a nearly empty oyster tong from the riverbed.

"Most of the fishermen I talked to say there's anywhere from a 35 to 50 per cent mortality rate," he said. "So that's our income cut almost by 50 per cent."

Perry said he is hearing there are more dead oysters than usual in the waters in the Mill River area.

"I just want to make sure that the minister of environment doesn't take a lax approach to this. And she has to understand that this is a huge issue and is very important to the fishers and their families and to the communities that rely on this industry to survive," said Perry.

The Department of Fisheries and Aquaculture couldn't comment yesterday on the state of oysters in the Mill River.

The province helped fund a sea lettuce harvesting pilot project in 2011, but didn't fund it this year after a provincial report determined the marginal success of the harvesting wasn't worth the cost.