Word: lampreys
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Dates: during 1960-1969
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...Middle Westerners who have watched game fish in the Great Lakes virtually disappear, the arrival of the cohos is the best news imaginable. Gone is the plentiful supply of lake trout, burbot, walleyes and pike that once made the lakes a fisherman's paradise. The fierce sea lamprey which invaded the lakes from the Atlantic by way of the Welland Canal, gradually wiped out the game fish. The lampreys were eventually controlled by chemicals, but in their wake came a 6-in. saltwater trash fish, the alewife (TIME, July 7, 1967), which monopolized the lakes. Four years...
Steelhead Hopes. Originally an ocean fish, the alewife could not penetrate very far into the Great Lakes until the 1930s, when rebuilding of the Welland Canal provided it with a convenient bypass around Niagara Falls. Even so, their numbers remained relatively small until the 1950s, when the sea lamprey-also an oceanic interloper-wiped the Great Lakes clean of the trout and burbot that were feeding on alewives. Too small a target for the lamprey (which is now being eliminated by chemical controls), and left with no natural enemies, the alewives promptly began a population explosion...
...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...
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...
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...