A Surfeit of Lampreys

Soon after she plunged into the water for her record swim across Lake Ontario last summer, Toronto's Marilyn Bell felt a gnawing sensation at her middle. A sea lamprey, one of millions of the slimy, eellike creatures that infest the Great Lakes, had sunk its teeth through her bathing suit, and was trying to attach its bloodsucking mouth to her body. It was as bad a moment as Marilyn had in the whole 21-hour ordeal. "I struck hard at it with my hand," she said later, "and my blow knocked it off."

Natural Barrier. Lake trout, for many years the richest catch of Canadian and U.S. fisheries in the Great Lakes, have no such defense against the Dracula-like lamprey. The bloodthirsty parasite, usually about 18 inches long, clamps its suction snout onto a fish, drills a hole through the scales with its tongue and multiple rows of sharp teeth, and clings tenaciously, draining the host's body juices until it is satiated, or the fish dies.

Originally a saltwater dweller, the sea lamprey moved up the fresh water of the St. Lawrence and into Lake Ontario to spawn, then developed a fresh-water species. The building of Canada's Welland Canal provided a detour around the natural barrier of Niagara Falls, and in the past 20 years the pests have begun to thrive in Lake Huron, Lake Michigan and, more recently, in Lake Superior. Multiplying enormously, with each female averaging 61,500 eggs, and feeding greedily, with each maturing lamprey devouring up to 40 pounds of fish, they have already wiped out the $5,000,000-a-year lake-trout fisheries at Lakes Huron and Michigan, and are now threatening those in Lake Superior.

Electric Fence. Canadian and U.S. scientists have studied many ways of fighting the destructive lamprey, even looking into the possibility of a domestic market for the lamprey's white, tasty but highly indigestible flesh.* Of all the tested antidotes, the most workable is an electrically charged fence that can be stretched across the Great Lakes' tributary streams, into which the lampreys swim to spawn. Other fish will turn away from the electric field, but the lamprey will swim against the fence and be electrocuted.

In Ottawa and Washington last week, lawmakers studied a proposed Canada-U.S. agreement for joint action against the lamprey. If the agreement is ratified, as expected, the two nations will invest nearly $3,000,000 (69% by the U.S., 31% by Canada) to erect lamprey-killing fences on all the spawning streams flowing to the Great Lakes. It couldn't happen to a nastier beastie.

* Henry I of England died in 1135 "of a surfeit of lampreys," a popular dish in the Middle Ages.

This file is automatically generated by a robot program, so reader's discretion is required.