The spotted gar is a patient fish. It waits in reeds and lilies for its prey to swim by. Long and slender, the alligator-nosed predator moves with stunning speed when its quarry swims past, gripping crayfish with razor-sharp teeth.
Yet while the spotted gar poses a threat to unsuspecting prey, habitat loss poses a threat to the spotted gar, which is an endangered species in Ontario.
“There are three known populations here and those would be in Point Pelee, Rondeau Bay and Long Point and some associated tributaries,” says Rebecca Dolson, who leads the Ontario Ministry of Natural Resources and Forestry in its spotted gar conservation work.”
While some spotted gars live in the northern part of Lake Erie, most live in the waters of Lake Michigan and the Mississippi River basin. Yet while their populations are small, spotted gars are good indicators of an ecosystem’s health.
“If you have a highly degraded ecosystem, you won't have spotted gar or other rare species,” says Nicholas Mandrak, a freshwater fish ecologist at the University of Toronto. “Those are the same ecosystems we depend on for things like drinking water.”
Researchers say human interference has contributed to the decline of the sensitive species.
The lack of available habitat is the gar’s biggest threat. The fish hides in wetland vegetation to hunt, and its eggs attach to those same plants. Southwestern Ontario has lost a tremendous amount of wetland — development has destroyed as much as 70 per cent of it.
And it’s a mystery to biologists why the spotted gar fares so poorly compared to the closely related longnose gar, which is relatively widespread in Ontario.
“That's sort of an outstanding question. Why does the longnose gar do so well over much of southern Ontario and the spotted gar so limited?” says Mandrak. “The interesting thing is if one is found in abundance, like in Rondeau Bay, we find relatively few of the other species.”
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The focus right now is on ensuring the three existing populations remain stable. Since they are so small, even the slightest loss of life could be catastrophic.
Mandrak says agricultural drainage ditches pose threaten the spotted gar and other freshwater species. Clearing the ditches can release sediment into the water, which obscures the gar’s vision and hinders its ability to hunt. The fine sediment can also disturb its eggs. Researchers are working on ways to clear the ditches that will not disturb the species.
But one of the most critical threats to the spotted gar comes from one of the province’s worst invasive plants: phragmites, a toxic perennial grass.
“The invasive species we're really concerned about in the future is phragmites. The issue with phragmites is it converts aquatic habitats into semi-aquatic habitats. When phragmites starts growing, gar will not be able to swim between [the reeds],” Mandrak says.
The reed spreads quickly and its roots discharge a toxin that kills other plants. Once established, phragmites quickly crowd out everything else and are difficult to eradicate.
“We think that under climate change, with Lake Erie water levels projected to go down, that that means all these wetlands will be filled with phragmites and that will reduce the total habitat for all fishes,” says Mandrak.