Victory on the Lakes

The bitter battle of the Great Lakes has been going on for 40 years, and for 40 years, from Erie to Superior, an ugly, blood-sucking monster has been winning. Chief losers have been the splendid lake trout--even though man himself has been their ally. But now news has come at last that the monsters are being beaten: a subtle chemical, cleverly used, has almost cleared Lake Superior of the invading fish-killing sea lamprey.

In its native ocean the sea lamprey is not particularly numerous, but ever since it appeared in Lake Erie in 1921, having worked its way up the Welland Canal past Niagara Falls, the repulsive eellike creature has been swarming in the lakes. With its round, suckerlike mouth lined with concentric rows of small, sharp teeth, it makes its living by attaching itself to the side of an unlucky fish. Its teeth rasp a hole; its powerful saliva corrodes the fish's flesh and keeps its blood flowing freely. Many fish die of a single lamprey attack.

Lively Larva. Lampreys prefer the larger fish, especially the tasty lake trout, which are also favorites of human gourmets. Lake by lake, as the lampreys advanced the trout disappeared. In 1935 the Lake Huron commercial catch was 6,000,000 lbs.; by 1945 it had dropped below 1,000,000 lbs. Later it fell to almost nothing. In Lake Michigan the story was the same. In Lake Superior, last lake to be invaded, the trout catch fell from 4,500,000 lbs. in 1951 to 368,000 lbs. in 1961.

First countermeasure tried by the fishes' human allies was electrical barriers across stream mouths to keep mature lampreys from swimming upstream to spawn. But many streams were already packed with growing larvae from lamprey eggs, so the U.S. Fish and Wildlife Service and the Canadian Department of Fisheries decid ed to destroy the larvae themselves. In search of a selective lamprey-larva poison, they tried more than 6,000 different chemicals on jars containing two lamprey lar vae, two bluegill fingerlings and two small rainbow trout. Some chemicals killed nothing; some killed both larvae and fish. Some killed two of the fish and one larva. Finally, in 1955, Chief John Howell of the service's Hammond Bay, Mich., lab, found a jar with its two larvae dead and its four little fish alive and frisky. The tricky compound that did the job best was 3-trifluormethyl-4-nitrophenol-- more handily known as TFM. Developed by Government Biologist Vernon Applegate, TFM reaches into the mud and attacks lamprey larvae. Millions of them pop out of their burrows and writhe helplessly for hours before they die.

Confident Service. TFM was first used in 1958 on lamprey-spawning streams that flow into Lake Superior, and by last spring the tide had turned against the slimy invaders. The number caught in traps as they tried to swim upstream fell to 12% of the 1961 catch. The adults are apparently dying off and are not being replaced by adolescent larvae.

The battle of the lakes is far from over, but the Fish and Wildlife Service is now hopeful of eventual victory. It has already started TFM treatment in streams that flow into Lake Michigan and Huron. As soon as each lake is reasonably safe, the service will release baby trout, confident that most of them will not be sucked to death by lampreys.

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