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Collapse of Commmercial Fishing

Over several decades the commercial yields from the Great Lakes fishery declined. Bigger boats and better nets could not compensate for a steadily declining number of fish. For several decades commercial fishers avoided the consequences of overfishing by abandoning one species of fish in favor of another. However, by the 1950's, overharvesting had decimated spawning stock of virtually all commercially marketable species. Already in steep and perhaps irrevocable decline, two environmental disasters caused the abrupt collapse of the Great Lakes fishery. The accidental introduction of the sea lamprey and the alewife into the upper Great Lakes essentially ended commercial fishing.

A sea lamprey is a relatively large, eel-like parasite that attaches itself to the side of a host fish. The lamprey lives by slowly sucking out the host's life fluids. Eventually the host fish dies and the lamprey moves on to a new victim. Not a native species, lampreys first appeared in the Great Lakes in the 1930's, apparently slipping through the Welland Canal that connected Lake Ontario with Lake Erie. A Sea lamprey attached to a Great Lakes fish Shallow Lake Erie was not much to the lampreys liking and for a time served as a barrier to their expansion. Eventually, however, lampreys made their way to Lakes Huron, Michigan and Superior, where they found hospitable breeding grounds, a plentiful supply of large fish, and no natural predators. Lampreys devastated the existing large fish populations, particularly commercially desirable trout and whitefish.

Alewives, another non-native species of fish, were accidentally introduced into Lake Ontario in the 1870's. They too apparently slipped through the Welland Canal and slowly entered the upper lakes. Predator species, particularly trout and whitefish, initially checked the growth of the alewife population. However, when a combination of overfishing and sea lampreys devastated the whitefish and trout population, the number of alewives began to expand rapidly. Alewives were too small to be of interest to the lampreys and proved far more efficient at feeding then many commercially desirable native species. Large schools of alewives devoured the natural habitat that chubs, herring, smelt, and other commercially desirable native species of fish had previously fed upon, causing the number of those fish to decline rapidly.

The combination of overfishing, the sea lamprey, and the alewife all but destroyed commercial fishing on the Great Lakes and left the natural fishery a shambles. White and Indian fishers alike found it impossible to make a living fishing commercially in the devastated lakes.

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