The smell of fish lingers in a high-tech laboratory, but it's not a native species in the water tanks at the U.S. Geological Survey's Hammond Bay Biological Station. Eel-like creatures squirm around one another, entangling themselves for a better place along the glass to suction their bloodsucking mouths.

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They make a nightmare scene not only in tanks at research stations, but also in the Great Lakes, where they wreak havoc on salmon and trout fisheries.

"Sea lampreys are a big deal for the ecology of the Great Lakes," said Roger Bergstedt, supervisor of the federal facility on the shores of Lake Huron, where a sterilization program is part of an effort to reduce or eradicate the invasive specie known as sea lampreys.

The parasitic fish is native to the North Atlantic Ocean and is suspected of making its way into the North American inland sea system through shipping canals. An oral sucker disc replaces a hinged jaw, and teeth are used to attach to the fleshy parts of large fish in the lakes.

Sea lampreys spawn in gravel beds in tributary rivers to the Great Lakes; young lampreys exist in streams between four and 10 years before they emerge and enter the lakes.

Officials used chemical treatments to kill larval sea lampreys for decades, along with various river dam methods, including low-level electric current and simple barriers. Hammond Bay researchers sterilize male lampreys and release them back into local waters.

Experimental pheromones are used to trap the creatures during spawning runs in tributary rivers. Males and females are separated so the males can be neutered and the females killed.

The release of sterilized males increases the ratio to normal males, creating greater competition for breeding, said Michael Siefkes, fisheries biologist with the U.S. Fish and Wildlife Service.

"If we just take the males and kill them, we can't use them against their own species," he said. "We're tricking the females, basically."

About 26,000 males were sterilized this year with an injection of a mutagenic chemical that affects embryonic development.

"This is all to rehabilitate the native species (of fish) we want to come back," Siefkes said.

Jim Johnson, manager of the state Department of Natural Resources Alpena Fishery Research Station, said Lake Huron's fishery lately is dominated by lake trout, rather than introduced Pacific, or Chinook salmon.

Lake Huron's Chinook fishery crashed in recent years, primarily because of a dramatic decline in the alewive population. The alewive is the prized game fish's chief food source.

Invasive species, such as sea lampreys and both zebra and quagga mussels, play a significant role in the ecosystem of the Great Lakes. Some types of fish are on the decline because mussels are changing nutrient levels on the lake floor, altering the food web.

Roger Barc, of Ossineke, annually works the weigh-in station at the Brown Trout Festival in Alpena. He pointed out a lamprey mark on a 11.5-pound Chinook, but said he's seen fewer of those marks over recent years.

Fisherman Tom Sharp, of Lachine, said he prefers to catch salmon but doesn't mind the comeback of lake trout.

"As long as that's not all there is out there," he said as he filleted a fish at the festival.