338 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



CHANGES IN PRODUCTION IN LAKE MICHIGAN AS RELATED TO 



FLUCTUATIONS IN THE ABUNDANCE OF WHITEFISH 



AND IN THE INTENSITY OF THE FISHERY 



In Lake Michigan as in Lake Huron the abundance of whitefish was abnormally 

 high near the beginning of the 1929-1939 period. The peak of abundance occurred a 

 year or two earlier in the more productive areas of Lake Michigan than in Lake Huron. 

 The abundance of whitefish was greater in 1929 than in any other of the 11 years in each 

 of the four districts of northern Lake Michigan, a region that accounted for 73.2 percent 

 of the 1929-1939 production. The maximum abundance occurred in 1929 in M-8 also. 

 The large increase in catch in 1929 (table 1 ) suggests strongly that the abundance in 

 this year was greater than that in 1928 and hence constituted the maximum for the 

 modern fishery. (Certainty on this point is not possible as the intensity of the fishery 

 in 1928 is unknown.) The maximum abundance of the 1929-1939 interval occurred 

 later in the remaining districts (1930 in M-6 and M-7, 1931 in M-5). However, these 

 districts were relatively far less important in the fishery of the entire lake than were 

 those in which 1929 was the year of peak abundance. Lake Michigan resembles Lake 

 Huron again in that a decline from the high level of abundance that existed early in 

 the period was to be expected. 



These resemblances between the data for Lake Michigan and Lake Huron are 

 fortunate, as they make possible a comparison of the course of the decline in Lake Michi- 

 gan, where the whitefish fishery was not disturbed violently by the use of deep trap nets, 

 and in Lake Huron where the introduction and widespread use of that new and efficient 

 gear brought about an utterly chaotic condition in the fishery. Accordingly, compari 

 sons of data for Lakes Michigan and Huron are emphasized in the present section. 



Several reasons may be advanced to account for the failure of the deep-trap-net 

 fishery to develop as extensively in Lake Michigan as in Lake Huron: (1) no exten- 

 sive or good whitefish grounds are found in Lake Michigan south of Frankfort; (2) 

 pound-netters and gill-netters rather than trap-netters were dominant on Lake Mich- 

 igan and opposed the use of deep trap nets (the Lake Huron deep-trap-netters who 

 entered M-7 in 1934 were driven out by local fishermen; shortly thereafter the Lake 



Table 17. — Annual fluctuation in the catch of whitefish per unit of fishing effort of gill nets, deep trap nets, 

 and pound nets in the various districts of Lake Michigan, 1929-1939 



