Scientists monitor sea lampreys on St. Clair River

Bob Gross
Times Herald

Port Huron — The contraptions stretching from behind navigational buoys in the St. Clair River are trap nets placed there to monitor sea lamprey populations.

“They’re fyke nets,” said Kevin Tallon, an assessment biologist with Fisheries and Oceans Canada in Sault Ste. Marie, Ontario. “They are deployed to catch out-migrating juvenile sea lamprey.”

Sea lamprey have a larval stage before they become parasitic adults, according to the Great Lakes Fishery Commission.

“They’re heading to their parasitic stage of their lives,” Tallon said. “In all likelihood they’ve grown as larvae in the St. Clair River. At a particular size and age they develop the parasitic mouth parts and eyes.

“They leave their natal stream and head out into the lake where they can find fish to feed on,” he said.

Sea lamprey are an invasive species. Their numbers began to climb in the upper Great Lakes with the deepening of the Welland Canal, which bypasses Niagara Falls and connects Lake Ontario with Lake Erie, in the 1900s.

After metamorphosis, adult sea lampreys spend the next 12 to 20 months feeding on fish, according to the Great Lakes Fishery Commission. The sea lamprey’s life cycle, from egg to adult, averages about 6 years, and may last as long as 20 years.

Tallon said the fyke nets are checked about three times a week by the agency’s partners from Walpole Island First Nation.

“They’re marked,” he said. “You don’t want to get too close to them because they are close to the buoy. … They are not going to be in there too much longer.”

He said the study, which is an attempt to index the population of juvenile lampreys in the St. Clair River and how that population contributes to lamprey numbers in Lake Erie, is in its fourth year.

“Lake Erie, it’s a challenge,” he said. “It’s been a challenge for us to get a handle on what is going on in the St. Clair River.

“This is our attempt to figure out if the St. Clair River contributes to the Lake Erie population of lampreys.”

He said control efforts have been effective in the Great Lakes.

“Throughout the Great Lakes, we have reduced the numbers (of sea lampreys) by 90 percent over the big collapse in the 1950s,” he said.