318 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



Table 3. — Production of whitefish in pounds according to gear in the State of Michigan waters of 



Lake Huron, 1929-1939 



[Percentages of annual yield in parentheses] 



' A considerable portion of this catch, entered in the original records under the heading, "Gear unknown," was taken by deep trap nets. 



It cannot be concluded that all of the production of deep trap nets represented 

 additional demands on the whitefish stock of Lake Huron or that an increase in yield 

 would not have taken place after 1929 without the operation of this gear. Substantial 

 increases occurred in the production of whitefish by both gill nets and pound nets in 

 1930, and the 1931 catch in these gears was above the 1929 level. Unquestionably the 

 output of gill nets and pound nets would have been even higher in 1930 and 1931 and 

 the subsequent decline in production in those two gears would have been less rapid had 

 not considerable numbers of fishermen abandoned the use of gill nets and pound nets 

 in favor of the much more efficient deep trap net. On the other hand, the fact that 

 deep trap nets produced more whitefish in every year of the 5-year period, 1931-1935, 

 than did all gears combined in 1929, and did so, as will be shown later (p. 330) in the 

 face of a rapid decline in abundance after 1931, suggests that this gear possesses capabil- 

 ities for the capture of whitefish far greater than can be attributed to either gill nets 

 or pound nets. (Superiority of deep trap nets over pound nets is due largely to the 

 greater range of fishing depths of the former. See pp. 331 and 332.) Although the 

 deep trap net cannot be held to be solely responsible for the increase in production that 

 took place after 1929, the conclusion is justified, nevertheless, that the increase would 

 have been much smaller had this gear not been fished. 



The superiority of the deep trap net for the capture of whitefish is indicated 

 strongly by the speed with which it replaced other gears. In 1929 deep trap nets ac- 

 counted for only 6.0 percent of the total yield of whitefish in Lake Huron. Two years 

 later in 1931 they took more than half the total and by 1933 were responsible for more 

 than 80 percent of the catch. Deep-trap-net production as a percentage of the total 

 yield fluctuated about the 80-percent level for 5 years (1933-1937) and declined only 

 with the virtual collapse of the fishery in 1938 and 1939. 



The deep trap net became at some time the dominant gear for the capture of 



