Knowledge of the presence and relative abundance of the species listed 

 thus far is based on records of the harvest of these species by commercial 

 fishermen. Species not of great commercial value were, of course, also pre- 

 sent in the lakes. A complete list of all species known to have been 

 present in the lakes would be too long to include for the purposes of this 

 paper. Our knowledge of changes in abundance of a few of these species, 

 however, is sufficient to warrent their inclusion. An abundant forage 

 species in the deeper water of all the lakes was the fourhorn sculpin 

 ( Myoxocephalus quadricornis ) . The slimy sculpin ( Cottus cognatus ) in- 

 habited intermediate depths in all lakes. The inshore waters contained a 

 variety of species of several families, especially the Cyprinidae. Among 

 the more abundant species were the emerald shiner ( Notropis atherinoides ) 

 and the spottail shiner ( Notropis hudsonius ) . 



Thus, when settlement began in the first half of the 19th century, the 

 lakes were occupied by a supposedly stable community of fish species which 

 inhabited all niches from the deepest waters of the subartic Lake Superior 

 to the shallow bays and marshes of Lake Erie. 



Environmental Conditions 



Physiochemical conditions of the lakes were not measured before the end 

 of the 19th century. Beeton and Edmondson (1972) used as a basis for evalu- 

 ating the "natural" chemical condition the limited chemical data available 

 about 19U0 as indicative of the pristine quality of the lakes (Table 2). 



TABLE 2. ESTIMATED AVERAGE CONCENTRATION OF DISSOLVED 

 CHEMICAL CONSTITUENTS IN THE GREAT LAKES 

 PRIOR TO 1900 (EXPRESSED IN MG/LITER) 3 



198 



