Hot Fence

The slimy, unattractive sea lamprey, which spends its life gnawing holes in fish, has practically conquered the Great Lakes. Since the first invasion of lampreys by way of the Welland Canal (TIME, June 16, 1947), they have almost wiped out the lake trout and are now going after the whitefish. The loss in trout alone, according to the U.S. Fish & Wildlife Service, is costing fishermen some $3,200,000 a year, and the lampreys have only begun.

Last week came the first good news for fishermen, the first bad news for lampreys. The Cook Electrical Co. of Chicago announced that it had developed for the Government a lamprey-killing electric fence which works fine on laboratory lampreys and shows promise of killing them in the wild.

The approved way to attack a pest is to study its life cycle in hope of finding a weak spot. Observers noted that the lamprey, an eellike creature about two feet long, reaches maturity in the Lakes and then migrates up the rivers to spawn. The young are fragile larvae that spend three years burrowing in the river mud. Then they develop into "neophytes" and start down the rivers to their hunting grounds in the Lakes.

Starting too soon may be a mistake that will cost the lampreys their conquest of the Great Lakes. In April, when the young lampreys are on the move, the water is still so cold that no baby fish are abroad. The observant Cook Co. designed an electrified fence to throw across the rivers. Neophyte lampreys passing between its meshes are electrocuted. If the fence is taken away before the water gets warm, baby fish are unharmed.

Killing the neophytes headed for the Lakes might eventually wipe out the lampreys, but Cook is also trying to figure out a way of dealing with adult lampreys headed upstream to spawn. The trouble is, lampreys move upstream at the same time as valuable spawning fish. The Cook people are looking for something that will annoy and delay lampreys. If the lampreys could be made to hang back, they could be safely electrocuted after the fish had passed by.

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