and bays. The drainage of marshes, however, may have been a significant 

 factor in the loss of the northern pike as an important commercial species 

 in Lake Erie. The establishment of the two marine species, smelt and 

 lamprey, was too recent to have had a measurable impact on other fish 

 species by 1925. 



Environmental and Cultural Changes, 1925-1950 



Several catastrophic events affecting the Great Lakes fish stocks 

 occurred during this period. The most damaging event was the invasion by 

 the parasitic sea lamprey of all the upper Great Lakes. After at least 50 

 years in Lake Ontario, the lamprey made its way into Lake Erie in 1923 

 where it did not flourish because of the lack of suitable spawning streams 

 and limited deepwater environment. In 1932 the first sea lamprey was re- 

 ported in Lake Huron; 4 years later the lamprey was in Lake Michigan; and 

 by 1946 the first report was made of a sea lamprey in Lake Superior (Table 

 6). Three years after the first sea lamprey was reported in Lake Huron, 

 the production of lake trout started to decline (1935), and by 1946 (Table 

 4) the commercial fishery for this species in Lake Huron proper was 

 finished, although the fishery in Georgian Bay lasted another 9 years. 

 Lake trout production began to decline in Lake Michigan in 1943 (7 years 

 after the first lamprey was reported); by 1950 production dropped below 0.1 

 million pounds (Table 4), and the species was virtually extinct 3 years 

 later. Only 18 years passed from the time the first sea lamprey was re- 

 ported in Lake Huron (1932) until the species was commercially extinct in 

 Lakes Huron and Michigan. 



The demise of the lake trout population in Lake Ontario and the role of 

 the sea lamprey is more complicated than in the upper lakes. Whether the 

 sea lamprey was endemic to Lake Ontario (Christie, 1972), or became 

 established after the opening of the Erie Canal (Smith, 1974), at least 75 

 years passed before the lake trout production began its final decline 

 (1928). A substantial fishery continued, however, for another 10-12 

 years. The species was last reported in the commercial catch statistics as 

 late as 1964 (Baldwin and Saalfeld, 1962, with supplement). That the sea 

 lamprey was a strong factor in the loss of lake trout in Lake Ontario is un- 

 disputed; the reasons why the struggle lasted so long remain a subject of 

 speculation. 



The sea lamprey's favored prey was the lake trout, but other species as 

 well were victims of this marine invader. Larger individuals of lake white- 

 fish, ciscos, lake herring, suckers, and burbot were attacked by the sea 

 lamprey. The production of burbot (never a prime commercial species) began 

 to decline in Lake Ontario in 1930, in Lake Erie in 1947, and in Lakes 

 Huron and Michigan by 1948 (Table 4). The burbot population became commer- 

 cially extinct in these lakes about 1960. 



Other species also began declining during this period, although the de- 

 clines were not related to the sea lamprey. The sauger began declining in 

 Lake Huron (primarily Saginaw Bay) in 1935; 2 years later the species was 

 commercially extinct. Beeton (1969) gave the reason for the decline as the 

 development of an environment not suitable for the sauger or the Saginaw 



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