Habitat loss leaves future of Georgian Bay’s trophy muskie fishery in question

By FishSens Staff on September 26, 2014

Tucked away along the remote, folding coast of eastern Lake Huron lays some of the best muskie fishing going. But the trophy waters of Georgian Bay are changing, and a new study raises questions about the future of the fishery.

Reports of 50-inch muskie are common on Georgian Bay, which In-Fisherman ranked among “The World’s Mightiest Muskie Waters” in September 2013.

That’s still the case, according to John Paul Leblanc, doctoral candidate in biology at McMaster University in Ontario and author of the study. “It still has a trophy muskie fishery,” he said. “The paper isn’t all doom and gloom.”

But a combination of dropping water levels and shoreline development appears to have ruined a set of coastal marshes in South Eastern Georgian Bay as muskie nursery habitat, according to the study. In 1981, the Ontario Ministry of Natural Resources documented 16 nursery sites in the Severn Sound area that supported young-of-the-year muskie. When Leblanc and his colleagues returned to those sites in 2012 and 2013, they found absolutely none remaining.

Part of the problem appears to be changes in the plant species that make up the habitat. Young muskie rely on a diversity of plants that provide structure throughout the water column. Many of the plant species that provided that in 1981 were less abundant in 2013.

“The gist of it is that these wetlands have been substantially changed,” Leblanc said.

A young-of-the-year muskie netted in a different area of Georgian Bay (Credit: John Paul Leblanc)

Part of that change has been brought on by sustained low water levels since 1999 that reached a record low in January 2013. An earlier study by Patricia Chow-Fraser, a professor of life sciences at McMaster who also supervised Leblanc’s study, estimated that fish have lost access to 25 percent of the coastal wetland habitat in eastern Georgian Bay that was available at the historical high water level.

Meanwhile, more marinas, cottages and docks have been built in the area, Leblanc said. That sort of development has been strongly linked to declining muskie reproduction.

“When these sites were first identified in 1981 by the Ontario Ministry of Natural Resources, the guys that wrote up the first paper emphasized that these locations should be protected from human development,” Leblanc said. “Based on our reassessment, this didn’t happen. The protective measures just aren’t in place.”

An extended dock compensates for the low water level on Georgian Bay. (Credit: John Paul Leblanc)

The lack of young muskie isn’t for lack of trying. Leblanc said telemetry studies have shown Georgian Bay muskies are loyal to their spawning grounds and many return to the same wetlands year after year. That appears to be the case in these degraded areas, but the habitats can’t support young fish after they hatch.

It’s difficult to say what this means for the muskie fishery. A lack of data on the bay’s adult muskies makes it hard to gauge how the population has responded. And despite the loss of nursery habitat in these 16 sites, there are plenty of other spawning sites across the bay, which is roughly the size of Lake Ontario. Water levels have ticked up recently, but with the potential for climate change to bring more long-term declines, this could be a sign of things to come.

“This is a relatively small subset, but it may be serving as somewhat as a litmus for the overall habitat quality,” Leblanc said.

The study is published in the Journal of Great Lakes Research.