Lampreys put a bite on lake trout
Written by Green Bay Press-Gazette   
Thursday, 10 August 2006 14:56

Lake trout, once the dominant predator on Lake Michigan, are so rare these days that salmon have replaced them as the fish of choice whenever a backyard boil is in order. While most longtime big-lake anglers admit today's salmon and steelhead are far more fun to catch, high-fat lake trout have a one-of-a-kind taste after being boiled with potatoes, salt and onions and smothered in melted butter.

"They're a little better tasting, a little more moist," said Denny VanDenBerg of Kewaunee, who has been boiling fish for almost 50 years. "They might fight like a log, but then again, so do walleyes."


Brian Frerk of Green Bay gives away almost all of the salmon and trout he catches while fishing with his 6-year-old son, Josh.


He may not fully understand, then, the love affair with lake trout by those who grew up with them when they were the only game in town in the 1960s or who targeted them in spring or whenever nothing else would bite on slow days from the 1970s to the 1990s.


The Frerks captured something Tuesday off Algoma, however, that may be playing a role in the huge drop in lake trout numbers over the past decade — a 24-inch sea lamprey attached to a chinook salmon.


There may be more lampreys in Lake Michigan than any time since efforts to control them started in the 1960s, said Mark Holey, project leader for the U.S. Fish & Wildlife Service's Fishery Resources office in Green Bay.


The St. Mary's River, between lakes Superior and Huron, got much of the blame for the initial surge in lamprey numbers a decade or so ago. Then, several years ago, holes big enough to allow lamprey passage were found in a dam on the Manistique River in Michigan's Upper Peninsula.


The river, the largest watershed in the U.P., is difficult to treat, with few barriers above the first dam. Those waters were treated in 2003 and 2004, and Holey said he expected lake trout numbers to improve this year.


However, many anglers have yet to catch a lake trout this summer. Others have landed only one or two. It once was common to get that many in a single trip while targeting deep-water salmon.


An increasing number of lamprey scars and live lampreys attached to salmon, steelhead, brown trout and even a jumbo perch on Green Bay have anglers concerned.


When a sea lamprey attaches to its prey, it uses its tooth-covered tongue to drill and suck blood from its source. A type of anticoagulant in its saliva is injected so that the sea lamprey is able to keep the wound open until it gets full.


After that, the target fish has only a slight chance of survival; most die from an infection in the wound, with an estimated six of seven dying.


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. That led to the discovery of the lampricide known as TFM, which was effective enough that biologists believe the population was cut by 90 percent.


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. Average size of adults is 12 to 22 inches.


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

 
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