Saalfeld, 1962). After 1910 production never exceeded 25,000 pounds and 

 averaged near 15,000 pounds for many years. In Lake Erie production 

 dropped from 1 - 5 million pounds in the late 1800's to less than 10,000 

 pounds after 1910 (Baldwin and Saalfeld, 1962). Similar magnitudes of de- 

 cline occurred during the same period in Lake Huron, Michigan, and Superior. 

 The cause-and-effect relationship apparent between watershed and stream 

 modification and Atlantic salmon extinction was not as direct with the 

 sturgeon. The environmental requirements of the sturgeon were not as 

 narrow as those of the Atlantic salmon; however, the slow growth rate and 

 late maturity of the sturgeon were also factors in this species, inability 

 to recover from even low exploitation rates. 



Christie (1972) also lists the blackfin Cisco ( Coregonus nigripinnus ) 

 as a species that became either extinct or greatly reduced in Lake Ontario 

 before 1900. Wells and McLain (1972) infer a sharp decline in the 

 abundance of this species in Lake Michigan in the early 1900's. The black- 

 fin was considered commercially extinct in Lake Superior by 1910 (Lawrie 

 and Rahrer, 1972). This species of Cisco inhabited the deep, open waters 

 of the lakes; consequently, environmental modification of the tributary and 

 watershed was not a factor in their decline. This species was the largest 

 of the ciscos, and selective exploitation for it was the probable cause of 

 its decline (Wells and McLain, 1972). 



The lake trout population in Lake Erie was also decimated during this 

 period. Hartman (1972), in discussing this species in Lake Erie, states: 

 "Perhaps the decline of the lake trout population to near extinction best 

 illustrates the effect of essentially one stress: intensive exploitation." 

 Apparently, environmental stress was not a factor in the decline of lake- 

 dwelling species during the 1800's. 



In addition to the effective loss of at least one species during the 

 1800's, several new species became abundant. Christie (1972) listed the 

 following species as becoming established in Lake Ontario before 1900: 

 alewife ( Alosa pseudoharengus ); gizzard shad ( Dorosoma cepedianum ); brown 

 trout ( Salmo trutta ); carp ( Cyprinus carpio ); and the goldfish ( Carassius 

 auratus ) . Some of these species were also introduced to the other lakes 

 during this period. There was a flourishing fishery for carp in Lake Erie 

 by 1899, when over 3.5 million pounds were landed (Baldwin and Saalfeld, 

 1962). 



Environmental Changes (Age of Physical Alterations) 



Man's effect on the Great Lakes ecosystem in the last half of the 19th 

 century was dramatic and permanent. He removed the forest, built dams, 

 constructed mills, directly exploited the fish, and opened new and more 

 direct passage between the ocean and the lakes, as well as between Lake 

 Ontario and the upper lakes (Figure 3). 



The effects of these physical modifications of the environment ranged 

 from immediate (Atlantic salmon extinction) to long-term (invasion of marine 

 species). The Erie Canal, which provided a connection between the Atlantic 

 Ocean and Lake Ontario, was opened in 1819 and extended to Lake Erie in 



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