Musky nurseries wiped out in Severn Sound

By Kate Harries AWARE News Network November 14 2012

Severn Sound is no longer a rich musky spawning ground.

In 1981, researchers from the Ontario Ministry of Natural Resources surveyed 100 wetland sites at the southeastern end of Georgian Bay and identified 20 of them as productive musky nurseries.

This past summer, researchers from McMaster University returned to 16 of the 20 nursery sites and found no evidence of successful reproduction among one of Lake Ontario’s largest predators and most prized sportfish.

“No young-of-year muskies were found at any of the historical nursery sites,” researcher Jean Paul LeBlanc told a meeting organized by Sierra Club Ontario. 

“Southeastern Georgian Bay has lost a substantial amount of critical musky habitat.”

The 1981 nursery sites were located along the eastern shore of Severn Sound, from Honey Harbour down to Sturgeon Bay, north of Waubashene. 

The dramatic change follows 13 unprecedented years of record low water levels, as well as an increase in human development. At the meeting, held November 10 in Toronto, organizer Mary Muter said that she has had advance notice from the US Army Corps of Engineers that an all-time record low may be set in the next month.

Leblanc noted that some of the nursery sites had lost more than fifty per cent of their wetland area.

Since 1981, significant changes to the aquatic community have adversely affected the musky. The first is the arrival of the round goby, an alien invasive species from Eurasia, introduced around 1990. 

Musky broadcasts spawn their eggs and provide no parental care, so there’s nothing to prevent the rapidly expanding round goby population from quickly consuming all the eggs. Even fish like largemouth bass, which do guard their nests, are vulnerable to the round goby. “If the parent leaves the nest, the round goby can clean it out within minutes,” Leblanc said. 

Another change is in the composition of the aquatic plant community which, with a shallower slope due to lower water levels, has become homogenized with no variation in plant species between growth at the shoreline and in deeper waters.

“There’s no edge,” Leblanc said.  This puts musky at a disadvantage. “Musky are ambush predators, they sit and wait in cover, they are highly associated with edge habitat.”

Because musky is a long-lived species (up to 30 years), the impact of the failed reproduction in formerly abundant coastland nurseries has yet to be felt, he said.

Furthermore, local anglers report that smaller muskies are still being caught. “New research is needed to determine where muskies might be spawning successfully so we can set those sites up for protection,” he said.