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Great Lakes Article:

Sea lampreys causing havoc on fishery
By Kevin Naze
Green Bay Press-Gazette
Posted online July 14, 2005

A multi-million-dollar fight against an enemy that kills more trout and salmon than sport, commercial and tribal fishers combined continues more than 40 years after it began.

Sport anglers concerned over few lake trout in the catch in recent years and increased sightings of sea lampreys on salmon have a good reason to be: According to the Great Lakes Fishery Commission, the number of lamprey spawners in Lake Michigan has tripled in the past decade to somewhere between 150,000 and 200,000 spawners.

“It is obvious there are more lampreys in Lake Michigan than at any time since (after) the initiation of control efforts,” said Mark Holey, project leader for the U.S. Fish & Wildlife Service’s Green Bay Fishery Resources Office.

The lamprey, an eel-like invader that latches on to fish with an oral disc, sharp teeth and a grasping tongue, threatens a sport and commercial fishery worth an estimated $4 billion to $5 billion.

Holey said it is believed the primary cause for the increase is a faulty dam with holes big enough for lamprey to get through on the Manistique River in Michigan’s Upper Peninsula.

“Actually, the initial increase was thought to have come from the St. Mary’s River, between lakes Superior and Huron,” Holey said. “However, once that river was treated, it was apparent the lamprey numbers in Lake Michigan were not decreasing.”

Holey said the Manistique — the largest watershed in the U.P. — is a difficult river system to treat, with few barriers once lampreys get above the first dam.

In response to high marking rates on Great Lakes fish, the Fishery Commission treated the Manistique in 2003 and 2004 which should produce noticeable results in lake trout numbers by 2006, Holey said.

“It just goes to show how fragile the fishery that anglers enjoy and rely on really is to lamprey predation, one of the original invasive species,” Holey said. “The entire balance of the Great Lakes fisheries would change dramatically should lamprey control be relaxed or not adapt to new challenges. It also illustrates how important it is to keep new invasive species out of the Great Lakes at all cost.”

Early this month, sport troller and tournament angler Michael Collins of McFarland had already reeled in five salmon with lampreys attached two at Racine, two at Algoma and one at Milwaukee. Many other fish have had scars resulting from run-ins with the parasitic predators.

“I’ve been fishing Lake Michigan for over 20 years and have never seen as many salmon with lamprey marks,” said Collins, a past member of the Lake Michigan Fisheries Forum, an advisory group to the Department of Natural Resources.

Through the years, very few lampreys stayed attached on fish he had hooked, he said.

“Each of my last three trips I have had fish with lampreys still on, and that clearly represents a drastic change that threatens our fishery,” Collins said after an outing at Algoma July 2.

Before chemical treatments began in 1958 in Lake Superior streams and 1960 in Lake Michigan, lampreys devastated a fishery already sliding from overharvest by commercial netters. Lake trout production in Lake Michigan dropped from 7 million pounds annually to zero, and populations in the remaining lakes were reduced to small remnants of historic levels.

During the 1950s, scientists tested almost 6,000 compounds to identify one to which larval sea lampreys were especially sensitive. The resulting discovery of the lampricide known as TFM was effective enough that biologists believe the population was cut by 90 percent.

The never-ending battle to continue international funding for the war on lampreys has taken many twists and turns, ranging from a reduction in lampricide use to an increase in electrical and low-head barriers, traps and the release of sterilized males.

Between them, the U.S. and Canada spent close to $100 million in the 1990s alone in an effort to control sea lamprey numbers.

Lampreys are most vulnerable during their worm-like larval stage, when they burrow in the sand or silt bottoms of Great Lakes tributaries for three to seven years or more. As adults, they spend 12 to 20 months in the lake, killing an estimated 20 to 40 pounds of fish each before returning to rivers to spawn and die.

Like most exotic invaders, lampreys have no natural predators. A native to the North Atlantic Ocean and many of its tributaries, they were discovered in Lake Ontario around 1835, then Lake Erie in 1921, Lake Huron in 1932, Lake Michigan in 1936 and Lake Superior in 1946.

Niagara Falls had served as a natural barrier until the construction of the Welland Canal in 1829 for the shipping industry.

Spawning typically occurs in late spring or early summer, and one female can produce 60,000 eggs. Biologists estimate about 14 percent of them are likely to be deposited in the nest, and once there, they have about a 90 percent chance of survival.

Great Lakes anglers, an estimated 800,000 of them, are the biggest beneficiaries of sea lamprey control, and many believe it’s only a matter of time before they’ll be asked to contribute directly to the multi-million dollar fight.


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