2 MARINE AND FISHERIES 



5 GEORGE v., A. 1915 

 ENVIRONMENT AND DISTRIBUTION. 



The information at present available concerning Georgian Bay fishes is not 

 sufficiently extensive to permit of comparisons being made between Georgian Bay 

 and other parts of the Great Lake system, or between the different parts of the 

 drainage area of which Georgian Bay is the collecting basin. It is important, 

 however, to recognize certain chief factors which may be operative in one local- 

 ity or another and especially in that at present under consideration. 



(1) Though forming an almost enclosed body of water, Georgian Bay is an 

 integral part of the Great Lake system; conditions which apply to the Great 

 Lakes will also apply to this area, except for local influences of antagonistic or 

 modifying nature. 



(2) With the exception of the North Channel of Lake Huron, and Lake Superior, 

 Georgian Bay is peculiar in having its two principal shores underlaid by rock 

 formations of fundamentally different type. Geological differences are the basis 

 of topographic and environmental differences, and when pronounced, as in this 

 area, may profoundly modify the distribution of species. 



In explanation of this feature, it may be pointed out that the entire eastern 

 and northern shore of Georgian Bay, extending from the mouth of Coldwater 

 River, at the end of Matchedash Bay, northward to Killarney, falls within the 

 ancient Archean area of the northern part of the province. The western and south- 

 ern shore, on the other hand, including the south shore of Matchedash Bay, the 

 Saugeen Peninsula, and Manitoulin Islatid, is underlaid by sedimentary strata 

 of Silurian age. The southern part of this shore, especially in relation to Matche- 

 dash Bay, is also covered by an extensive deposit of glacial drift. The surface 

 features of the two main shores are different in almost all respects. 



(3) The Archean portion of the shore of Georgian Bay is part of an extensive 

 eastern drainage area of which Georgian Bay itself is the common outlet. The 

 water courses of this area are chiefly of the nature of basins, connected with other 

 levels by rapids and waterfalls which act as barriers against upward migration. 

 Differences in distribution have already been observed in this area, though only 

 certain of them appear to depend on this factor. 



(4) There is geological evidence that the area now occupied by this portion 

 of the Great Lake system is smaller than in former times. The south and east 

 shores were formerly situated at a considerable distance, respectively, south 

 and east of the present boundaries, the water area including on the eastern side 

 a part of the Archean district now occupied by an enormous number of more or 

 less isolated lakes. 



(5) This body of water had in former times, not only the outflow connection 

 to the south and west as now represented by Lake St. Clair, but also temporary 

 outlets eastward through the Trent and Mattawa valleys. The western parts 

 of these areas are now parts of the Georgian Bay drainage (cf. Goldthwait '10). 



Go Home Bay is a small indentation of the main eastern shore of Georgian 

 Bay, lying within the Archean area, at a distance of approximately 25 miles north- 

 westward from its southern border as recognized on the shore line by the mouth 



