Clumps of zebra mussel shells remained scattered along the southeast shores of Lake Winnipeg Friday afternoon at Island Beach.

The invasive species is nothing new to Lake Winnipeg, but the amount of zebra mussels in the area has left some full-time residents and cottagers concerned.

Area residents told CTV News zebra mussels have appeared along the shoreline before, but never in numbers like what people saw wash up on the beach last week.

"It's the first year we've seen the masses of them," said Manitoba Association of Cottage Owners president Dave Crabb. "This year there seems to be quite an explosion."

"What we really need to do is seriously look at the spread," said Crabb. "I don't think much can be done for Lake Winnipeg."

Island Beach resident Josiph Majer said his grandchildren like to swim in the water, but the zebra mussels may put a damper on one of their favourite activities.

It's still safe to go in the water, but the mussels have sharp edges and stepping on them can result in cuts.

"Some places, you get about 3, 4 inches high (clumps of zebra mussels), some places hardly any, but still there's some there, so bare feet, it's no more," said Majer. "I'm not happy that we can't use the beach like we used to, just bare feet and having fun.”

The washed-up mussel shells are a sign that there are a lot more zebra mussels in the lake, said biologist Eva Pip.

She said the mussel population is multiplying quickly and could have a harmful effect on freshwater clams and fish in the lake.

The province said Friday anyone moving boats to winter storage needs to stop at invasive species inspection stations.

“As we near the end of the open water season, we ask that Manitobans take extra precautions to ensure they are not transporting aquatic invasive species when moving watercrafts,” said Sustainable Development Minister Cathy Cox.

“The best and most effective measures to reduce the spread of AIS come from Manitobans taking action to clean, drain and dry their watercraft and other vessels, and dispose of water and bait in a way that does not move unwanted invasive species to another water body.”

Inspection stations have recently been set up at Grand Rapids, Eriksdale, Swan River, The Pas and in the RM of St. Clements, the province said. There is also a decontamination unit at Selkirk Park boat launch.

More information is available online.

Manitoba's Aquatic Invasive Specialist visited the Island Beach area this week but was unavailable to speak with CTV News on Friday.