DECLINE OF LAKE TROUT IN LAKE MICHIGAN 



83 



I Mean annual production in thousands of pounds. 



The large drop in production in M-3 from 1891- 

 1908 to 1929-43 was reflected in a decrease of 10.9 

 in the percentage contribution of the district to the 

 total output of the State of Michigan waters (from 

 43.8 to 32.9 percent). The only other district in 

 which the percentage decreased was M-1 (a drop 

 of but 0.5). The remaining six districts experi- 

 enced increases in percentage that ranged from .2 

 m M-2 to 5.6 in M-5. These changes in the vari- 

 ous districts resulted in a noticeable shift of produc- 

 tion toward the south. Districts JM-1, M-2, and 

 M-3, which, as noted earlier, contributed 60.3 

 percent of the total in 1891-1908, accounted for 

 only 49.1 percent in 1929^3. The proportion for 

 M^ through M-8 rose correspondingly from 39.7 

 to 50.9 percent. A similar shift in production of 

 lake trout toward the south was described for the 

 State of Michigan waters of Lake Huron by Hilo 

 (1949). 



Rather than burden the present section, which 

 deals with production trends in 1929-49, with 

 numerous micxplained exceptions to general state- 

 ments, it is believed desnable to anticipate discus- 

 sion that logically should appear later and describe 

 at this tune the peculiar situation in district M-1 

 that makes the data for that area so difficult to fit 

 into a general account of the lake-trout fishery of 

 the State of Michigan waters of Lake Michigan. 

 This difficulty has its origin in the circumstance 

 that M-1 is not true "lake-trout water" and that 

 the commercial catches of the species are normally 

 part of the production in a fishery aimed primarily 

 at the taking of lake whitefish (Coregonvs clupea- 

 formis). As a result, the intensity of the fishery 

 for lake trout, and consequently the production as 

 well, are controlled to a large degree by the condi- 

 tions of the whitefish fishery. This relation is 

 brought out rather forcefully by the data of table 



933837—51 2 



6 on the production, abundance, and fishing in- 

 tensity for the two species in M-1 over the period 

 1929^9. 



The salient features of table 6 are summarized 

 briefly in the foUowing sentences. First, the pro- 

 duction of whitefish in M-1 normally is consider- 

 ably greater than that of lake trout. In only 2 

 of the 15 yeai-s of the base period 1929-43 was the 

 take of lake trout the greater, and the 15-year 

 average for whitefish was nearly three times that 

 for lake trout. In the years after 1943 the ad- 

 vantage of whitefish was much greater than in the 

 earlier, more nearly nomial period. Second, the 

 availability of lake trout and the intensity of the 

 fisher}^ for that species did not exhibit the positive 

 con-elation that would be expected if abundance 



Table 6. — Comparison of lake-trout and whitefish fisheries in 

 district M-1, 1929-49 



' In thousands of pounds 



' Percentage of 1929-43 moan. 



' Operations with large-mesh gill nets only. 



