Lamprey numbers skyrocket

The eel-like, blood-sucking, fish-killing sea lamprey is making an unexpected comeback on Lake Superior.

Lamprey numbers have exploded -- nearly doubling in western Lake Superior -- during the past year as state and federal biologists try to determine whether the increase is a temporary spike or a major problem for lake trout and other fish.

And scientists are starting to battle lamprey larvae in new locations, including in the lake itself and not just in streams.

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

"It's not just the trapping numbers," he said. Lamprey-caused wounds also are up, especially on the larger trout to which lamprey attach. In the lake's western area, the number of lamprey scars on big lake trout is up more than 400 percent -- 26.9 scars per 100 trout compared to 6.4 per 100 trout last year.

Sea lampreys, native to the Atlantic Ocean, swam into the Great Lakes when the Welland Canal was built in 1919. They devastated populations of fish. They attach themselves to lake trout, like this one, often leaving the fish too weak or wounded to survive. Submitted by Minnesota Sea Grant.

"We're also finding lamprey marks on other species -- like suckers, whitefish and herring -- and that's a clear sign there are a lot of lamprey out there," Seider said.

The U.S. Fish and Wildlife Service is seeing the problem across Lake Superior. The agency's overall lamprey population estimate jumped 23 percent from 2004 to 2005, said Jessica Richards, marine biologist at the U.S. Fish and Wildlife Service biological station in Marquette, Mich.

"It's a significant increase, especially in the west," Richards said, noting lamprey numbers in western areas of the lake jumped from 35,000 last year to more than 62,000 this year.

Great Lakes Indian Fish and Wildlife Commission surveys show a general increase in lamprey spawning in the Bad River for nearly a decade, with major increases since 2002.

So far, the spike in lamprey hasn't appeared to significantly reduce lake trout numbers. But scientists say that could change quickly if lamprey aren't brought back under control.

Dave West, a Superior-based charter fishing captain, said big lake trollers definitely are seeing more lamprey and lamprey scars on lake trout.

"We're seeing more medium-size and small lamprey than before. It seems like it's been getting worse the last couple of years," said West, who has 15 years of experience on Lake Superior. "We're seeing lamprey on salmon and even walleye, and we didn't see that before."

Superior is the only Great Lake with a major lamprey increase, Richards said. While Lake Erie had a minor increase this year, all other Great Lakes were down, with Lake Michigan showing about half as many lamprey this year as last.

TWO NEW SOURCES

Scientists are focusing on a few specific culprits, and are already working to stem the lamprey tide. The first hot spot seems to be a few Ontario streams near Thunder Bay that hadn't previously held lamprey. In recent years, and between surveys by field researchers, the streams began pumping adult lamprey into Lake Superior.

Chemicals applied this fall at gravel spawning grounds in streams will kill this year's crop of lamprey larvae, which would have moved into Lake Superior to start killing fish in about two years.

Until then, 2006 could see even more lamprey than this year.

"We're treating more streams this year in the western lake, and we should see the results by 2007. It should be a... substantial drop in 2007," Richards said. "We see the problem out there and we're working on it."

Another phenomenon may be harder to deal with. Scientists believe some lamprey larvae may be thriving in Lake Superior itself, and in near-shore estuaries, and not just in streams, as previously believed. The larvae may wash out of the streams where adults spawn and, although not anticipated by scientists, be surviving to adulthood when they feed by attaching their tooth-filled mouth to the sides of fish.

For the first time, scientists are planning to use a chemical lampricide spread on open water to kill lamprey larvae. Using a granule-based chemical, dropped by helicopters, has worked to kill lamprey larvae in the St. Mary's River near Sault Ste. Marie, Richards said.

Scientists hope attacking the newly discovered lamprey sources will curb the recent increase and that there isn't a larger, undiagnosed problem brewing.

"We're trying to deal with these populations that we've never treated before. We think that's where this population spike is coming from," Richards said.