The number of eel-like creatures, which feed by attaching their teeth-filled mouths to lake trout and other fish, is up 23 percent in Lake Superior since last year and has doubled in the western part of the lake, according to state and federal biologists, who are taking new measures to battle the lamprey.

In a lamprey trap in the Brule River, which feeds into Lake Superior, crews trapped 9,478 lampreys this year, three times last year's catch and the most ever in the barrier's 20-year history, said Mike Seider, a fish biologist for the Wisconsin DNR.

Scientists are also finding more wounded fish, including suckers, whitefish and herring. The lampreys haven't significantly reduced the number of lake trout, but that could change quickly if the increase isn't stemmed, scientists said.

Jessica Richards, a Michigan-based marine biologist for the U.S. Fish and Wildlife Service, said lamprey numbers in western areas of the lake jumped from 35,000 last year to more than 62,000 this year.

No other Great Lake had a major lamprey increase, Richards said. While Lake Erie had a minor increase this year, the other Great Lakes saw a decrease, with Lake Michigan showing about half as many lampreys this year as last.

Scientists have identified several hot spots they believe are mostly responsible. One is a series of Ontario streams near Thunder Bay that previously didn't hold lampreys but now are pumping adult lampreys into Lake Superior.

At the spawning grounds, chemicals were applied to kill this year's crop of lamprey larvae, which would have showed up as fully grown creatures in about two years. Before then, scientists said, 2006 could see even more lamprey than this year. For the first time, scientists also plan to use a chemical lampricide on open Lake Superior water to kill the creatures.