Photo: Sea lamprey have a large oral disk filled with sharp, horn-shaped teeth that surround a toothed tongue.
Many Great Lakes invasions of non-native species begin unnoticed—but not so with one of the most destructive invasions of all, the attack of the sea lamprey.
Fish with sea lamprey attached
The scourge of the Great Lakes fishery, the lamprey is believed to have appeared in Lake Ontario for some time, but was temporarily restrained by Niagara Falls from reaching the other Great Lakes. But after improvements to the Welland Canal, which bypasses the Falls, on November 8, 1921, just over a century ago, an Ontario commercial fisherman trolling in central Lake Erie noticed a lamprey much larger than the native, non-destructive lampreys that he occasionally netted. The University of Toronto identified it as a sea lamprey, and the invasive species’ war on the Great Lakes fishery was on.
“Throughout the next two decades, sea lampreys spread, unchallenged, throughout Lakes Michigan, Huron and Superior,” the Great Lakes Fishery Commission says, “wantonly killing hundreds of millions of pounds of fish along the way.”
“Throughout the next two decades, sea lampreys spread, unchallenged, throughout Lakes Michigan, Huron and Superior,” the Great Lakes Fishery Commission says, “wantonly killing hundreds of millions of pounds of fish along the way.”
Looking like something out of a horror movie, sea lamprey have remained largely unchanged for more than 340 million years. Sea lamprey have a cartilaginous skeleton and a large oral disk filled with sharp, horn-shaped teeth that surround a toothed tongue. The oral disk allows them to attach to, and the toothed tongue allows them to rasp a hole into the side of, a host fish and feed on its blood and other body fluids. Each lamprey can kill up to 40 pounds of fish over its 12-18 month feeding period.
Only one in seven Great Lakes fish survived lamprey attacks, and 85% of fish that survived had scars signaling they had been attacked. Before the lamprey invaded, anglers harvested about 15 million pounds of lake trout in the upper Great Lakes each year. By the early 1960s, the catch had dropped to approximately 300,000 pounds, about 2% of the previous average.
Calling the lamprey invasion “arguably one of the worst ecological disasters in history,” the Great Lakes Fishery Commission has a more positive view of the response to the invasion by Canada and the United States.
The establishment of the Fishery Commission itself was part of the response, created by the two nations in 1955 to find an answer to the lamprey invasion. In a remarkable feat of research, scientists tested thousands of chemical compounds, looking for one that would primarily target lamprey, until they discovered the lampricide TFM. “It’s easy to kill fish but hard to kill just what you’re after,” says Marc Gaden, communications director for the Fishery Commission.
Sea lamprey populations are down by 90-95% from their historical highs in most areas of the Great Lakes, “certainly beyond the wildest expectations of those who established the program in 1954.” Gaden says. Barriers and dams also control sea lamprey.
To maintain the success in controlling sea lamprey, the Canadian and U.S. governments spend over $20 million a year on lampricide treatments and other control measures—and will probably have to continue control efforts in perpetuity. The rule with Great Lakes invasive species is that once they’re here, they’re here to stay, although with some species you can knock down their populations to manageable numbers.
“Sea lampreys—just like zebra mussels—are major ecosystem disruptors,” says Cory Brant, author of Great Lakes Sea Lamprey: The 70-Year War on a Biological Invader. “If we let up, they will make a comeback and feed on any large-bodied fish they can find, including lake trout, Chinook salmon, and the endangered sturgeon.”
“Sea lampreys—just like zebra mussels—are major ecosystem disruptors,” says Cory Brant, author of Great Lakes Sea Lamprey: The 70-Year War on a Biological Invader. “If we let up, they will make a comeback and feed on any large-bodied fish they can find, including lake trout, Chinook salmon, and the endangered sturgeon.”
Gaden remains optimistic. “The annual appropriation is a small, small fraction of the $7 billion Great Lakes fishery, and it’s good that elected officials see the clear connection between low lamprey numbers and the valuable fishery, leading to bipartisan support for the Commission’s lamprey control work.”
And there are promising new lamprey control approaches. Says Gaden: “We are on the cusp of using pheromones and repellents in the field as control techniques. Our scientists are honing in on concentrations needed to affect behavior.” The Fishery Commission also is beginning to explore genetics as a control technique.
