GENERAL INTRODUCTION 

 Need for Investigation 



The fishes of the Great Lakes constitute a natural resource of immense 

 commercial and recreational value. Conservation of this resource has become 

 a piajor problem confronting various governmental agencies in Canada and the 

 United States. 



For a period of 50 years the average annual production of commercial 

 fish in the Great Lakes was 100,000,000 pounds, and in many years Lake Erie 

 accounted for roughly one half of the total c atch. As early as the decade 

 prior to 1870 there was definite evidence of a decline in the abundance of 

 fish, but production has been maintained at a high level by increasing the 

 intensity of fishing effort, and by seeking the less desirable species. 



Concern has been felt particularly for the fishery of Lake Erie because 

 of the great decline in the highly prized whitefish and cisco. Miner (187U) 

 reported the presence of a lucrative whitefish fishery in Detroit River, but 

 in the last decade of the century, this fishery was abandoned as a commercial 

 venture and there was evidence of depletion in Lake Erie (Rathbun and Wakeham, 

 1897). With the decrease in the supply of whitefish, the cisco was sought 

 with increasing intensity, and this species held first place in production 

 in Lake Erie until it suddenly became almost commercially extinct in 1925 

 (Van Gosten, 1930). Certain other species have shown unmistakable evidences 

 of depletion. For more detailed information on the fishery, the reader may 

 refer to Koelz (1926), U. S. Tariff Commission (1927), Higi^ins (1928a and 

 1929), Van Gosten (1929a), and Fiedler (1931). 



Following the virtual collapse of the cisco fishery, fishermen, conser- 

 vation officers, and fisheries biologists alike realized the necessity of a 

 scientific investigation to determine the cause or causes of the decline of 

 the fishery, and to determine possible remedial measures. Since depletion 

 was first noted, two possible explanations have been especially prominent 

 in discussion of the problem: (1) excessive fishing and destructive methods 

 of fishing, and (2) pollution of the tributaries and of the lake by domestic 

 sewage and industrial wastes. Fishermen, particularly, were persistent in 

 their claim that pollution had made parts of the lake unsuitable for fishes. 

 It was held that the deposition of sludge had rendered large areas unfit for 

 spawning; that there was not sufficient oxygen in the water; and that the 

 quality and quantity of food had declined. Father, many claimed that 

 poisonous substances had caused the death of large numbers of fish. Attention 

 was directed to the western part of the lake because of a number of condi- 

 tions which make it especially subject to pollution, and because of its impor- 

 tance in the fishery. 



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