TRAVERSE CITY, Mich. (AP) — Parasitic sea lampreys may have established a self-sustaining population in Michigan's Inland Waterway, a nearly 40-mile-long chain of lakes and rivers popular with anglers and boaters, federal scientists said Thursday.
It would be the first confirmed case in the Great Lakes region of the invasive lampreys spending their entire life cycle in an inland waterway network instead of migrating to one of the lakes after reaching adulthood, said Nick Johnson, a research ecologist with the U.S. Geological Survey's Hammond Bay Biological Station on Lake Huron. That could mean the job of containing them will get costlier and more complicated, he said.
The findings are preliminary but show the importance of determining whether the same thing is happening in other inland lakes, said Marc Gaden, spokesman for the Great Lakes Fishery Commission, which spends about $21 million a year keeping lamprey numbers down.
"These critters are quite destructive," Gaden said. "If we find they're having an impact on inland lakes, or that inland lakes are serving as a source of lamprey for the Great Lakes proper, we'll need to address that."
Tim Cwalinski, a Michigan Department of Natural Resources fisheries biologist, said it's likely that sea lamprey have been living undetected in waterways upstream from the Great Lakes for years. There's no evidence they are doing heavy damage to Inland Waterway fish, he said.
Sea lampreys, native to the Atlantic, reached the Great Lakes through shipping canals in the past century and feasted on trout and other prized species. The eel-like predators fasten their round, disk-like mouths, rimmed with razor-sharp teeth, to the sides of fish and suck their blood.
Fully grown lampreys feed for 12 to 20 months before swimming up rivers to spawn, then dying. Their wormlike offspring spend up to six years as larvae, concealed in stream beds, before heading to the lakes as adults.
Federal agencies keep them in check with methods such as spreading poisons in rivers and trapping and sterilizing males. Dams and other barriers help by preventing them from reaching spawning areas.
Lampreys in their larval stage have been found for years in three streams that feed Burt and Mullet lakes, which are part of the Inland Waterway in Cheboygan and Emmet counties near the tip of Michigan's Lower Peninsula. Scientists have assumed they were reaching the waterway by swimming up the Cheboygan River from Lake Huron and bypassing a lock and dam, although it wasn't clear how, Johnson said.
But recent evidence suggests some lampreys are surviving poison treatments in those streams, then slipping into Burt and Mullet lakes and remaining there instead of continuing to Lake Huron, he said. Anglers have provided photos of fish with lamprey wounds caught in those inland lakes, and an adult lamprey was nabbed in Burt Lake last August.
"So even if we identify their escape route around the Cheboygan lock and dam and close that door, we still may have a battle with sea lamprey to wage in the inland waterway itself," Johnson said.
That would be bad news because the budget for lamprey control is already stretched, Gaden said.
But a silver lining would be that agencies could mount an all-out effort and determine whether it's possible to completely eliminate lampreys from waterways, Johnson said. The existing program has knocked down the population by 90 percent, but experts have considered eradication a pipe dream because a single female can lay up to 100,000 eggs at once.
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