DECLINE OF LAKE TROUT IN LAKE MICHIGAN 



79 



1920 



1945 



Figure 1. — Production of lake trout in Lake Michigan, 1889-1949. Upper solid line = entire lake; broken line= 



Wisconsin; lower solid line = Michigan. 



The take of lake trout fluctuated about a still 

 lower level in 1927-39 when the average total for 

 the lake was 5,293,000 pounds, 1,714,000 pounds 

 below the mean for 1912-26 and 2,937,000 pounds 

 less than that for 1890-191 1. The catch exceeded 

 6 million pounds only once in 13 years (6,394,000 

 pounds in 1929 — again a sharp deviation of the 

 Wisconsin figure from the characteristic level was 

 responsible for the extreme) ; it was between 5 and 

 6 million pounds in 6 years, and less than 5 million 

 pounds in 6 years. The lowest catch of the period 

 was 4,763,000 pounds in 1936. Michigan, Wis- 



consin, and Indiana contributed to the decline 

 from 1912-26 to 1927-39 with decreases of 616,000, 

 1,107,000, and 71,000 pounds, respectively. The 

 Illinois catch, on the contrary, was increased by 

 80,000 pounds in the latter period. 



The lake-trout fishery of Lake Michigan enjoyed 

 a brief period of heightened productivity in 1940- 

 44 when the take exceeded 6 million pounds in 

 every one of the 5 years and averaged 6,578,000 

 pounds, or 1,285,000 pounds above the 1927-39 

 mean. To a considerable extent the improvement 

 can be attributed to the large increase of 713,000 



