The Resurgence of Sea Lampreys

In an alarming twist, invasive sea lamprey populations have surged in the Great Lakes, reigniting concerns among fishermen and biologists. Michael Attard, the owner of Angler’s Edge Fishing Charters, has witnessed an unsettling increase in these parasitic 'vampire fish' since the COVID-19 pandemic struck. Once a rare nuisance, they are now a common sight, with multiple lampreys clinging to marred salmon and trout pulled from the depths of Lake Ontario.

“Clients are shocked,” Attard notes while fishing out of Bluffer’s Park in Scarborough. The sight of these unusual creatures sends children scurrying to the safety of the boat’s far end. “They are a nasty fish,” he adds, encapsulating the unease felt among everyone involved in the fishing community.

Historical Context and Control Efforts

The resurgence of sea lampreys is particularly disheartening given the historical context—several decades earlier, a frantic cross-border effort between Canada and the U.S. had successfully curbed their population. After nearly wiping out native fish, the invasive species sparked the formation of the Great Lakes Fishery Commission in the 1950s, tasked with eradicating them. A strategic partnership emerged, leading to the successful application of lampricide—a chemical that effectively targets lamprey larvae while safeguarding other fish species.

However, when the COVID-19 pandemic emerged, it disrupted these essential control measures. Restrictions hindered normal lampricide applications across tributaries, leading to a dramatic decline in extermination efforts. The estimated sea lamprey population in Lake Ontario skyrocketed from around 5,500 prior to the pandemic to an alarming 56,000 by 2021.

Impact on the Ecosystem

The sea lamprey, native to European waters, introduced chaos to the Great Lakes ecosystem in the early 1900s. With no natural predators to keep their numbers in check and an abundance of vulnerable prey, they proliferated dramatically. The rise of this 'vampire fish' ultimately decimated populations of valuable native species, leading to the bi-national treaty aimed at restoring ecological balance.

Current Control Strategies

With the return to normal operations in 2022, biologists reported progress, as numbers started to decline again—down to about 22,000 in 2024. Andrew Muir, science director at the commission, remains cautiously optimistic, stating, “We anticipate those numbers will keep going down,” thanks to renewed efforts.

Researchers are exploring innovative methods to keep the sea lamprey population under control for the long term. One promising area involves disrupting the fish's keen sense of smell, essential for their mating rituals. Michigan State University is developing compounds that interfere with the pheromones released by male lampreys that attract females, potentially disrupting their spawning behaviors.

Further efforts include dismantling barriers that allow lampreys to migrate and spawn freely in river systems. For instance, authorities in Traverse City are working on the FishPass, an advanced river barrier designed to filter out invasive species using lights, bubbles, traps, and screens.

Looking Ahead

Reflecting on the pandemic-induced setbacks, Muir poignantly remarked, “This has been an unfortunate but really great example of what happens when you sort of rest on your laurels with respect to invasive species control. Because it does not take long for these animals to flourish without control.”

As Canada and the U.S. gear up to reassert their management strategies in the Great Lakes, the ongoing struggle against the relentless sea lamprey serves as a stark reminder of the delicate balance required to preserve native ecosystems and the devastating impact of invasive species. The fight is far from over, but renewed efforts offer hope for a brighter future in the Great Lakes.