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How do you lure in sea lampreys? With the smell of baby sea lampreys, MSU research finds

RJ Wolcott
Lansing State Journal

EAST LANSING - Sea lampreys are voracious blood-suckers. They'll latch onto any fish big enough to fit their mouths, which are swirling with rows of sharp teeth.

Around 10 million pounds of dead trout, cisco and other commercially sought-after fish across the Great Lakes are left in the invasive species' deadly wake every year, according to Marc Gaden, spokesperson for the Great Lakes Fishery Commission. A dime to half-dollar-sized gash in the host fishes' flesh serves as their calling card.

Chemical treatments, traps and barriers have greatly reduced the number of sea lampreys in the Great Lakes over the past few decades.

But Michigan State University's Weiming Li and his colleagues have found what could be a new weapon in the arsenal: a chemical found in the lampreys' offspring. 

Sea lamprey attach to large fish like trout and salmon, sustaining on blood and bodily fluids until either being shaken off by the fish or its death.

Li's lab recently identified a molecule released by lamprey larvae — a pheromone — that attracts male and female adults to suitable waterways for spawning.

The life cycle of a sea lamprey goes like this: Lamprey metamorphize and head out into the open water and feed on fish. One sea lamprey can kill 40 pounds of fish. After 12 to 18 months of feeding, it's time to reproduce. Lamprey larvae resting on the bottom of streams suitable for spawning send out a pheromone that brings adult males and females to them.

“Work has been done to show these kinds of chemical signals are indispensable for these animals to complete their life cycles,” Li said. Disrupting those signals has the potential to control sea lamprey and reduce dependency on current techniques like lampricide, a chemical used on lamprey larvae to control their population.

Sea lamprey were first observed in the Great Lakes in the 1920s and 1930s. They are an invasive species that causes significant losses for commercial fishermen.

He’s quick to point out that the research has been a cooperative effort between academic institutions such as MSU and Western Michigan University, federal agencies in the United States and Canada and private industry.

Their collective work identifying the pheromone which guides travel between open water and waterways ideal for spawning was published in July by Proceedings of the National Academy of Sciences of the United States of America.

The next step, Li said, is to find how other compounds excreted by the sea lamprey work together with the newly identified pheromone. In doing so, researchers could then focus on disrupting the system.

Sea lampreys were first spotted in Lake Erie in 1921, and made their way to Lake Michigan, Huron and Superior in the following decade and a half. At their peak in the 1950s, sea lampreys killed 100 million pounds of fish every year in the Great Lakes, Gaden said.

The damage amounted to five times that of the commercial catch in the northern Great Lakes, per the commission’s website.

“Nothing keeps them in check,” Gaden said. “They’re the killer bee version of the nice, productive, native honey bee,” noting that several lamprey species are native to the Great Lakes basin.

It got so bad that officials tried to market lamprey to fishermen and the public as a food source. The problems were myriad: sea lampreys are hard to catch, don’t freeze or transport well, don’t taste good to the North American pallet and often contain high levels of mercury.

The development of a pesticide that specifically targets the larvae of lamprey, along with refined trapping and restricting of bustling streams, reined the invader in. 

The public is less aware of the dangers posed by sea lamprey, in part, because control efforts have been so successful, Gaden said. Lessons learned are relevant to the ongoing efforts to keep Asian carp species from getting into the Great Lakes.

“It’s better to keep them out in the first place,” he said. "Once they’re in, whether its Asian carp, sea lamprey, or zebra mussels, the chances of getting rid of them are virtually nil.”
