152 Conservation Department 



Great Lakes through which to flow. Upon glaciation the fish life 

 of the area must either liave been destroyed or forced southward. 

 With recession of the ice sheet, fish could have gained access to 

 the great glacial lakes, since these overflowed southward into the 

 Mississippi drainage. Coleman^ states ''The Mississippi and its 

 tributaries supplied a harbour of refuge when the northern part of 

 the continent was ice-covered and lifeless, and colonized the lakes 

 and rivers which arose after the melting of the ice sheets." He 

 substantiates this view upon evidence of fossil mollusks and other 

 forms of life. Late stages in the melting of the ice uncovered 

 outlets lower than the Mississippi one, and the Great Lakes over- 

 flowed to the Atlantic. There was an invasion of the waters of 

 this ocean into Lake Ontario which may account for certain of the 

 differences between it and Lake Erie in relation to fish fauna. 



Ecological Data in Regard to Problems of Stocking. — The 



fact that each species has its own requirements as to conditions 

 of environment is of fundamental importance in the matter of 

 natural distribution and in the practical problems of stocking 

 waters with fish. The conditions as to food, shelter, spawning 

 grounds, chemical content of the water and temperature are de- 

 cisive factors. The size of stream or other body of water, the 

 type of current and bottom must be considered. The problem is 

 further complicated by the effects of competition between the 

 various species and by the activities of parasites, natural enemies 

 and of man. 



When the particular requirements for a species can be analyzed, 

 the problem of increasing its numbers becomes more simple. A 

 limited number of fishes has been studied thoroughly enough so 

 that waters may be successfully stocked with them. This is true 

 of the brook trout and a few others, but there are very many 

 species that are greatly in need of study as a guide to practical 

 problems of conserving them in a wild state and of increasing 

 the supply by fish cultural methods. 



In so far as possible, ecological data was gathered for all species 

 of fish collected. The type of bottom, current and the tempera- 

 tures were observed at each collecting station. Space forbids com- 

 plete tabulation of this data, but brief notes on the tj^pe of en- 

 vironment are given, for many species, in the annotated list. 



Food and Game Fishes. — Of the 116 species considered in the 

 annotated list, at least 36 are important in greater or less degree 

 economically, being used either in the commercial fisheries, or being 

 caught by anglers, or serving both purposes. General notes as to 

 such importance are given under the accounts of the various 

 species. The food and game fishes are : sturgeon, lake herring, 

 whitefish, brown trout, rainbow trout, steelhead trout, lake trout, 

 brook trout, buffalo mullet, common sucker, red-fin suckers (4 



» Coleman, A. P. Glacial and Post-Glacial Lakes in Ontario. Publications of the 

 Ontario Fisheries Research Laboratories X, 1922. 



