The number of parasitic sea lamprey in the Great Lakes is up because of COVID reduced control efforts.
During the COVID pandemic, the crews that work to suppress the fish-killing sea lamprey were not able to do as much work for a couple of years.
That’s because the pandemic forced some hotels to close, required social distancing, and other COVID-related barriers to the effort to suppress sea lamprey populations.
“And as a consequence of that, we now are seeing the results of those increased numbers of sea lamprey that have moved from the streams where sea lamprey breed and live their formative years and then moving out into the lake where they actually feed on our fish,” said Greg Clinchey with the Great Lakes Fishery Commission.
He says in some localized areas, the sea lamprey population increased as much as 300%, although the results varied around the Great Lakes.
The increase in sea lamprey because of reduced suppression efforts did show that control efforts are important to the Great Lakes fisheries.
“This is basically the real-world result of an experiment we always suspected but never dared to undertake. And that is to see what happens if we stop controlling sea lamprey,” Clinchey said.
While the sea lamprey is unlikely to ever be eradicated, the Great Lakes Fishery Commission works to keep the population of the parasite limited.
“We want to find numbers that allow fish populations to be stable and even to increase,” said Clinchey.
In Lake Superior, the decades long effort resulted in a restoration of the top predator fish, lake trout. Overfishing and sea lamprey combined to knock the lake trout population down by 95 percent in the first half of the 20th century.
In 1962, Canada, the U-S, and tribal nations agreed on a plan to restore the population. After decades of stocking the fish, and controlling the sea lamprey population, the lake trout population is restored in Superior. More difficult environmental challenges could prevent the lake trout from ever reaching sustainable levels in the other Great Lakes.
Even with the recent increased sea lamprey population, it’s still under control well enough to keep most fish species productive. Still, the Great Lakes Fishery Commission has determined that tighter controls than possible during the COVID pandemic are necessary to ensure fish harvests don’t plummet once again.
