Meet the ruffe, aggressive fish causing concern in the St. Marys River

A warning about an aggressive species that has been lurking in the waters of the Great Lakes, even though it’s not very big.

The Eurasian ruffe has recently been detected in the St. Marys River, outside of Sault Ste. Marie, and it’s making its way south causing concern among researchers.

Eurasian ruff (Gary Cholwek, U.S. Geological Survey, Bugwood.org)

"The Eurasian Ruffe is a small, freshwater fish and it’s a member of the perch family, so it’s native to Europe and Asia but it’s suspected to have been transported to North America, specifically Lake Superior, in the ballast water of ships arriving from Europe back in the mid-1980s," said Sydney Currier of the Invasive Species Centre.

"Its spread within the Great Lakes is likely due to heavy ship traffic between Lake Superior and other Great Lakes ports."

In the United States, ruffe has been found along the southern shore of Lake Superior, Lake Michigan and Lake Huron.

In Ontario, it’s been recorded near Thunder Bay and it’s spreading east along the northern shores of Lake Erie with Sault Ste. Marie being the latest place to detect it.

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"They’ve been around, but, now, they’re on the move and they’re going south," Currier said.

"The concern with ruffe is that they’re very aggressive competitors with our native fish, particularly our native sport fish. We’re talking yellow perch and walleye in particular because they compete with those sport fish for food and habitat and they also prey heavily on their eggs and the juveniles of those species. So this is really important from an economic and social point of view given those species and their importance to recreational fishing."

Eurasian ruffe are only about six inches long and they have a perch-like body, but what sets them apart is their sharp dorsal fin and the appearance of it looking like two phones. The fish also doesn’t have any scales on its head.

Currier said anglers are important and will be the first line of defence in keeping Eurasian ruffe from spreading.

"If you see a ruffe in the water or you catch one, it’s really important to take a picture, note the date and the location where you found it at and then don’t return it to the water. Call the invading species hotline and then kill the fish and put it in the garbage," she said.

The Invasive Species Centre said the number one thing anglers can do is know how to spot the ruff and make sure to drain their bilge and dry the boat when taking it in and out of water.

It is illegal to use ruffe as bait.