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A U.S. Fish and Wildlife Service crew will be hunting this week for live river monsters in Detroit.

But instead of the alligator gars, man-eating catfish and piranha featured on the cable TV show "River Monsters," it'll be searching the Detroit River for a different kind of monster — the sea lamprey.

"We search the river every 2-3 years," said Scott Grunder, supervisor of the federal agency's Ludington Biological Station. "So far it's a negative system, which is good. But we have to keep looking."

Beginning Wednesday, a Fish and Wildlife team will conduct tests to determine if sea lampreys live in the river. Grunder said the agency last searched the river for the underwater parasites in 2013.

Sea lampreys are eel-like, jawless fish native to the Atlantic Ocean. They are more than 340 million years old, but were first found in the Great Lakes in the 1920s.

Equipped with large sucking discs filled with teeth, they attach to other fish and feed on their fluids, often killing them. It's estimated a single lamprey can kill up to 40 pounds of fish during its feeding period, which lasts 12-18 months.

They also can have a long lifespan, most of it spent dormant on waterway floors. The suckers start out in eggs laid in gravel nests on the bottom of streams. A single female can produce as many as 100,000 eggs.

After hatching from the eggs as larvae, sea lampreys burrow into the sand and silt, where they can live for up to 20 years, feeding on debris and algae.

Once they emerge as adults, they'll spend the rest of their lives feeding on fish.

Grunder said the Fish and Wildlife Service treats nearly 500 of the Great Lakes' 5,000 tributaries for the parasites.

"The more we clean them up, the more we provide for fish passage, the more those (streams) are going to get invaded because sea lampreys like clean, cold water," he said.

They've been around for millions of years, Grunder said, and they're never going to be completely eradicated from the Great Lakes or their tributaries.

"We go after them in every one of their life stages," he said. "They're just a tough, adaptable critter."

He added it's impossible to treat each river and stream for sea lampreys every year. The agency doesn't have the people or resources to do it, and sea lampreys continue to get into lakes, rivers and streams from the St. Lawrence seaway through shipping canals.

To hunt for sea lamprey larvae in the river, crews will pour a chemical called Bayluscide into the water. Sand granules are covered with a fast-dissolving coating of the chemical or lampricide, which causes the larvae to leave their burrows and swim to the surface, where crews will collect them.

"It usually happens within an hour," Grunder said. "Since we began using lampricide in the late 1950s to control sea lampreys, we've knocked their population in the Great Lakes area back 90 percent. It's been very effective."

He said the lampricide won't harm humans or other fish. It is approved by the U.S. Environmental Protection Agency and Health Canada Pest Management Regulatory Agency.

Bob Burns, Detroit riverkeeper, said he's aware the Fish and Wildlife Service has used the lampricide in other streams and rivers around the Great Lakes for years.

Burns, who works for the Friends of the Detroit River nonprofit and monitors the river's health, said he doesn't know much about Bayluscide, other than "we've been told it only impacts sea lampreys and not other fish species."

Burns said he's seen lampreys attached to fish and scars left behind on fish in the river. However, he said, he's not sure if they were sea lampreys or one of the other four lampreys that live in the Great Lakes — chestnut, silver, American Brook and Northern Brook.

"I've seen lampreys on carp and I've seen them on coho and trout," he said. "They are having an impact on other fish. Obviously, we're in favor of lamprey control as long as the use of lampricide chemicals don't harm other fish species or organisms living in the Detroit River."

Grunder said if Fish and Wildlife crews find sea lamprey in the river, the number detected will determine the agency's next move.

"Depending on the severity of the infestation, we'll run the information through a computer model, which will go in with the data on Michigan's other streams and rivers," he said. "If the river is ranked high, in the top 10 or 20, it'll be put on the treatment list. But we don't expect that."

cramirez@detroitnews.com

(313) 222-2058

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