Clean Waters Mean New Threat For Fish
MILWAUKEE (AP) _ The sea lamprey, an eel-like parasite once barely able to survive in the polluted streams flowing into the Great Lakes, is staging a comeback in cleaner waters - and threatening a billion-dollar game fish economy in the process.
″The irony is we take care of one problem and this one comes around,″ said Charles Higgs, Lake Michigan district director for the Wisconsin Department of Natural Resources.
Environmental experts say the lampreys, which gobbled up much of the Great Lakes’ trout population in the 1950s, have reappeared in waters which until recently were too dirty to support them.
The U.S. Fish and Wildlife Service has identified several streams leading into Lake Erie and Lake Ontario where lamprey numbers are growing.
Also, the St. Louis River, which flows into Lake Superior past Duluth, Minn., is being chemically treated for the first time to ward off the lampreys.
In Wisconsin, the lampreys have been found in the Oconto and Peshtigo rivers, which feed into Green Bay. And officials are worried the culprits will make their way up the neighboring Fox River and ravage what is considered the nation’s best population of lake sturgeon, located in Lake Winnebago.
″Every year, there’s a few more streams with lamprey in them,″ said John Heinrich, who oversees the lamprey control program for the federal Fish and Wildlife Service in Marquette, Mich.
″As the waters become clean, they become more suitable for the lamprey,″ he said. ″We’re strong proponents for cleaner water, but the lamprey is an unfortunate byproduct.″
Lampreys, which are native to the ocean, entered the Great Lakes through the St. Lawrence Seaway in the 1920s.
Tom Jolliff, the sea lamprey unit leader for the New York Bureau of Fisheries, said a single female might spawn up to 100,000 eggs at a time. ″Even if one out of 100 makes it, you’ve got all kinds of lampreys,″ he said.
Despite efforts at curbing the lampreys, an estimated 680,000 are swimming in the Great Lakes; on the average, each lamprey kills 40 pounds of fish during its lifetime.
″It’s a constant battle,″ Higgs said, adding that environment officials fear the lampreys will increase not only in the lakes but also in the inland waterways.
″If something would impact the sturgeon population (in Lake Winnebago), it would take a long time to recover, if it recovers at all,″ said Dan Folz, a fish manager for the Department of Natural Resources in Oshkosh. ″It would be a substantial impact to the fish economy.″
The Fish and Wildlife Service estimates game fish are worth $1.4 billion each year to the economy of the Great Lakes region.
Poison has its risks as a method of combating the lampreys. In May, use of chemical lampricides led to the death of thousands of fish in a tributary of the Oconto River when the chemical mixed with low concentrations of oxygen and an unexplained high concentration of ammonia in the water. The incident was unusual, but nonetheless the potential exists for more accidents, Higgs said.
Other options include using physical barriers, such as a closed lock on a river, or installing grids in the water which emit electric currents that block the lampreys.
The Fish and Wildlife Service also might try to sterilize male members of the species and release them among other lampreys to prevent reproduction.
But Heinrich said there is evidence lampreys are spawning in areas where it will be difficult to control them. Normally, the lampreys swim up streams to spawn because they need a steady current, he said.
But last year, lampreys were found spawning in the Marquette harbor on Lake Superior using a current created by the discharge from a power plant.
Heinrich said this was the first time lampreys have been found spawning in one of the Great Lakes.