Great Lakes Invaders: Controlling Sea Lamprey Populations
Sometimes called the “vampires of the deep,” sea lampreys have all the makings of a formidable predator. Their mouths, complete with file-like tongues, are lined with more than 100 razor-sharp teeth. They stand on top of the food chain as apex predators, meaning they have few to no predators of their own. And just one of these creatures can kill 40 or more pounds of fish in its lifetime. Their M.O? Using their suction-cup mouths to attach to fish for long periods of time; feeding on their blood, body fluids and bodily tissues; and eventually killing their hosts.
Don’t worry—humans aren’t their typical prey, though you can see what it would be like to host one of these parasites in the cringe-worthy video below:
The Great Invasion
While people can swim without fear of these aquatic parasites, humans are affected indirectly by their populations. The Great Lakes has been fighting invasive sea lampreys since the mid-1900s, after the species entered the lakes and threatened the robust commercial fishing industry there.
Niagara Falls was once enough to block entry to the lakes, but once the Welland Canal opened in 1829, all bets were off. Sea lampreys first entered Lake Ontario in the mid-1800s, and then the upper Great Lakes in 1921, where they feasted on the abundant lake trout, salmon, whitefish, walleye, catfish and other fish. By the 1950s, they had virtually wiped out the commercial and recreational fisheries in the Great Lakes.
The U.S. Fish and Wildlife Service jumped into action, working with the Great Lakes Fishery Commission to execute a massive control effort that managed to reduce the lamprey population by 90 percent between the 1950s and 1960s. But maintaining that control still takes plenty of resources and techniques today. Lampricide, barriers and traps are just a few of the ways the Great Lakes Fishery Commission is working to sustain a healthy ecosystem in the lakes.
Lampricide is a common method for reducing sea lamprey populations. As you probably guessed from the name, it’s a chemical that effectively poisons this particular species but is nontoxic to other animals and humans. About 200 Great Lakes tributaries and lamprey nursery waterways are regularly treated with lampricides to take out larvae before they become parasitic.
Lampreys need the gravel and soft substrates found in tributaries to spawn, so the commission has implemented barriers throughout the Great Lakes to block access to these habitats. Some are low barriers that other fish can jump over, while others employ a “trap and sort” method. This strategy reduces the need for lampricide treatments.
Up to 40 percent of the adult lamprey population from a tributary can be captured with the use of traps that are built into or placed immediately downstream of lamprey barriers. While they don’t eliminate the need for lampricide treatments, they help keep populations in check and serve as a useful way to assess adult populations and gauge the success of the control efforts.
Pheromones and Alarm Cues
The Great Lakes Fishery Commission is investigating ways to use the sea lampreys’ keen sense of smell against them. The species releases pheromones to attract potential mates and also emits alarm cues upon death or injury in order to warn other lampreys of danger. Researchers are hoping to take advantage of this biological mechanism by using pheromones and alarm cues to lure adult lampreys to traps, unsuitable spawning habitat or areas that can be easily treated with lampricides.
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