Ben's Science Spotlight: A mouthful of ugly

This ancient, jawless fish can grow up to 3 feet long, sucks lymph and blood out of host fish, and can consume about 40 pounds of fish in its lifetime. They have no jaw, cartilage for bones, and are single-handedly responsible for the extinction of lake trout in all of the Great Lakes except Lake Superior. This is an amazing feat considering that the creatures being described have no hands to speak of. Sea lampreys are a species of ancient, jawless fish native to the eastern coast of the United States and are one of the most harmful invasive species that the Great Lakes have ever seen.

Before the creation of the Welland Canal in 1830, millions of pounds of lake trout were harvested every year. But when the canal connected Lake Ontario and Lake Erie, the parasitic sea critters swam their way across the lakes, feeding on most of the larger fish they could find.

“Lampreys are their own kind of species,” said Douglas Jenson, the Aquatic Invasive Species Program coordinator for the Minnesota Sea Grant. “They’ve really held onto their own evolutionary niche.” While they may look like giant leeches or eels, lampreys are more closely related to hagfish, another kind of lawless fish found in the oceans.

Sea lampreys hunt down their prey by scent, like a shark, and use their sucking mouth to latch onto a large fish like a trout or salmon. The lamprey then proceeds to bite into the fish with their many rows of teeth and suck out the lymph and blood of the host.

“A lamprey can consume about 40 pounds of fish in its lifetime,” said Jenson. “Only one in six fish ever survive being a lamprey’s host.”  These aquatic pests have also been known to be about 20 inches long in Lake Superior. But they can also get up to three feet long in their native east coast region.

While they have been spotted in and around the north shore of Lake Superior, lampreys pose little threat of feeding on people. But fishermen pulling them off of their caught fish have been known to be bit by lampreys if they detach the lamprey and then hold onto it for too long.

“Their numbers are down to around five to ten percent what they used to be,” said Don Schreiner, the DNR’s area supervisor for the Lake Superior Fisheries Office. “But that’s only because of our constant efforts to control their population.”

Methods used to limit lamprey in the Great Lakes include building barriers to limit their movement, creating traps in order to catch them, and spreading pesticides on streams where they’ve been known to spawn.

Sea lampreys are excellent hunters, relying on scent to track their prey in the murky waters of the Great Lakes. They release pheramones to find mates and spawning areas, the same chemicals are being collected and used to combat their ever-present numbers.

“There is really a two-way effect we feel in dealing with lampreys,” said Schreimer. “When we build dams or fences to stop the flow of lampreys into other lakes and streams, we also cut off routes that the fish can use. It also goes the other way around in that, as we try to clean up the St. Louis River of industrial waste, we find that lamprey are moving into the cleaner waters.”

Currently there is research being done on lamprey pheromones. Sea lamprey will release pheromones in order to find mates and their offspring in the murky waters of the Great Lakes. By harvesting and releasing these pheromones in traps or in habitats not conducive to laying eggs, the state is able to limit the amount of reproduction that lampreys have.

Most caught lampreys are thrown into a landfill after being caught, but a novel approach was brought up to try and do something with the tossed creatures.

“Sea lampreys are a delicacy in Portugal and Spain where they can go for $22 to $25 a pound,” said Jenson. “Back in 2005, the Minnesota Sea Grant got the idea to take all these caught lamprey and try to export them over there to make a little money off of these things. We had everything ready to go, but it ultimately failed because there was too much mercury found in the lamprey to pass the European standards.”

Control of the lamprey population costs about $25 million every year.

“We try to think of it as an upside down pyramid.” said Schreimer. “You’ve got tourism, anglers, commercial fishing, and all that supported on keeping the lamprey population down. So that’s about $25 million to support a $7 billion industry. There doesn’t seem to be any magic bullet to taking care of the lamprey problem, but if we stop our efforts, things could get a whole lot worse.”


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