Population Increases, 1925-1950 



The population in the Great Lakes basin had exceeded 18 million by 1950 

 (Beeton, 19b9), an increase of approximately 40% in 25 years (Table 3). 

 Again, the greatest numerical growth was in the Lake Erie basin with an in- 

 crease from 5.8 to 8.5 million (48%). The population in Lake Erie's basin 

 was 46% of the total population and, combined with the Lake Ontario popula- 

 tion, accounted for 62% of the total. The population in the Lake Michigan 

 basin was nearly 5 million in 1950. This continued concentration of people 

 in Michigan, Erie, and Ontario lake basins, with the associated municipal, 

 industrial, and agricultural wastes, was the primary cause of the accele- 

 rated rate of increases in dissolved chemical constituents in these lakes. 



Lake Erie—Demise is Heralded 



The sudden collapse of the Lake Erie lake herring fishery in 1925 

 awakened the public to the need for scientific investigations into the 

 causes of the precipitous decline. The magnitude of the decline in lake 

 herring production was from an average of 26 million pounds per year in the 

 previous decade to 6 million pounds in 1925, to less than a million pounds 

 in 1929. 



Since environmental factors were thought to be the cause of the lake 

 herring decline, two intensive limnological studies (Wright, 1955; Fish, 

 1960) were initiated in 1928. Wright (1955) found unfavorable conditions 

 in rivers and estuaries, but concluded that environmental changes in the 

 open waters of the western basin of Lake Erie in 1928-30 had no adverse 

 effect on the decline of fish stocks. Fish et al . (1960) also found no 

 environmental basis for the decline of lake herring in the central and 

 eastern basins in 1928-30. Although neither investigator found measurable 

 environmental degradation in the open lake, their studies for the first 

 time established a scientific base line of data on benthic organisms, plank- 

 ton, and dissolved oxygen. The base line has subsequently been invaluable 

 in measuring environmental changes in Lake Erie. 



The effects of the sea lamprey on the lake trout stocks (previously 

 discussed) were recognized in the 1940's, and attempts to control the 

 lamprey began in 1946. Another decade passed, however, before an organized 

 and substantial program was developed to control this destructive parasite. 



CHANGE AND REHABILITATION (1950-1975) 



Fish Stocks 



Changes in abundance of fish stocks are continuing in 1975; however, 

 many changes are now deliberate and controlled. Uncontrollable changes in 

 native species (usually decreasing in numbers) and in introduced species 

 (usually increasing in numbers) frequently occurred during the past 25 

 years . 



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