The Great Lakes’ Longtime Nemesis is Going Down

Double agents. Plugged noses. Phermone-bait traps. Scientists’ latest schemes to control the North’s blood-sucking sea lamprey population are working wonders.

When it comes to invasive species in the Great Lakes, efforts to halt the spread of the Asian Carp have generated a lot of buzz.

But there’s been an ongoing, persistent, under-the-radar effort to control an old nemesis — the fish-killing sea lamprey — that’s proven to be stunningly successful.

“The sea lamprey population in Lake Michigan is currently at about a 25-year-low,” said Andrea Miehls, communications contractor of the Great Lakes Fishery Commission at the Hammond Bay Biological Station in Presque Isle County. “The sea lamprey population in Lake Huron was at a 30-year low in 2015. The population increased slightly in 2016, but the Lake Huron population is still very close to the 30-year low recorded in 2015. These are all positive signs for sea lamprey control in the Great Lakes and protection of Great Lakes fisheries.”

The latest efforts against the eel-like lamprey are designed to control the population, rather than eradicate it, according to Nick Johnson, a research ecologist for the U.S. Geological Service.

“I compare it to a farmer doing weed control,” explained Johnson. “When you see a farm field, it looks great, and you don’t see the weeds because the farmer controls them. But if the farmer doesn’t take care of the field, you’ll soon see the weeds again. The farmer won’t eradicate the weeds — they’re still there — but he’ll control them. Lamprey control is the same.”

The rivers and streams that feed the Great Lakes are the focus of lamprey control. There are some populations of lamprey, according to Johnson, that stay in rivers and streams and never venture out to the Great Lakes. They maintain a breeding population in those rivers. Scientists are busy targeting those lampreys, working to interrupt their breeding cycle.

“Lampricide has been used in the past, and that kills them in the rivers, but eventually they become resistant,” said Johnson, who has been working this year on two lamprey control programs in northern Michigan, both with the goal of controlling lampreys.

The first involves the use of a lamprey pheromone — named 3KPZS — that was isolated and identified at Michigan State University, Johnson’s alma mater.

Late in 2015, the Environmental Protection Agency registered 3KPZS as safe for use in nature, making it the world’s first pheromone for biological control of a fish and opening the door for control methods that use the lampreys own pheromones to trick them. Traps baited with the pheromone are up to 50 percent more successful than unbaited traps. The pheromone research was conducted on the Betsie and Manistee Rivers.

Researchers also measure the natural pheromones in the streams to find lampreys, then use traps, low-voltage electric fields, and other control techniques. “The challenge is trying to optimize dosing requirements so they work best,” said Johnson.

Perhaps, the most effective approach may be to block the lampreys’ ability to smell the pheromone in the first place. In the lab, scientists have plugged lampreys’ noses with latex. Those who could not smell had little chance of finding spawning sites or mates. Researchers are looking for a chemical that would permanently block the lampreys’ ability to smell pheromones — a chemical trick to plug up their noses.

The second experimental research project involves injecting a compound into male lampreys that have been trapped by the U.S. Fish and Wildlife Service. The sterilized males were fin-clipped for identification, then released into three popular northern Michigan rivers — the Pigeon, the Sturgeon and the Maple. These males are not interested in feeding, only mating. The experiment is expected to last for three years. 

“People sometimes get worried when we release lamprey, but these are adult lamprey who have stopped feeding on fish,” said Johnson. “They go out, find lamprey we couldn’t catch, and mate with them. Then they die — both male and female. It’s like they’re double agents.”

 Sea lampreys use their suction-cup mouths filled with grasping teeth to latch on to larger fish and suck out vital bodily fluids. By traveling up ship canals, the lampreys reached all of the Great Lakes by 1939. In the 1950s, lampreys virtually wiped out the lake trout population before scientists began a vigorous campaign of using lampricide to combat the invaders. Over several years, researchers tested more than 6,000 chemical compounds and found two that kill sea lamprey larvae without significantly harming other aquatic life.

That lampricide treatment was a great success, reducing the number of Great Lakes lamprey by 90 percent according to Miehls. Sea lamprey once killed almost 103 million pounds of Great Lakes fish every year. Today that number is less than 10 million pounds annually, according to the Great Lakes Fishery Commission. “Even though the numbers are down, the lampreys still destroy more fish than all the fishery operations,” Miehls noted.

Before the Great Lakes Fishery Commission began controlling sea lamprey, it’s estimated there were 2.5 million of the slippery invaders in the Great Lakes. Current data shows a total of about 215,000 lampreys in the Great Lakes with 82,000 in Lake Superior, 79,000 in Lake Huron, 30,000 in Lake Michigan, 17,000 in Lake Ontario and 7,000 in Lake Erie.

Northern Lake Michigan, northern Lake Huron and eastern Lake Superior are considered “hot zones” where numbers of lamprey are found.

“Fortunately, the sea lamprey control program in the Great Lakes is one of the best control programs for an invasive vertebrate species anywhere in the world,” said Miehls.

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