310 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



Although the selections of the periods for the preceding comparisons, based on the 

 examination of the statistical data, were to a certain extent arbitrary, reasonable 

 changes in the years included in these periods would not affect the validity of the 

 general conclusion that the increase in the production of whitefish was greater in 

 the State of Michigan waters of Lake Huron than in other Great Lakes areas. 



Despite the known risks involved in the estimation of changes in abundance from 

 changes in production, the ratios of the preceding paragraph would suggest the possi- 

 bility that the recent increase in the abundance of whitefish may have been somewhat 

 higher in the Michigan waters of Lake Huron than in other Great Lakes areas. 

 Information from other sources, however, proves that such an assumption would be 

 utterly invalid. The higher production in the Michigan waters of Lake Huron (as 

 compared to other waters) was made possible by the introduction of a new and marvel- 

 ously efficient gear, the deep trap net. The use of this net made possible a tremen- 

 dous increase in fishing intensity. No doubt an increase in catch would have 

 taken place without the use of deep trap nets; however, it was deep-trap-net opera- 

 tions that accounted for the relatively greater heights of production attained in the 

 Michigan waters of Lake Huron. 



The description of the annual fluctuations in the yields and abundance of white- 

 fish and in the intensity of the whitefish fishery in the Michigan waters of Lakes Huron 

 and Michigan, 1929-1939, presented in part II, is concerned largely with the effects 

 of deep-trap-net operations on the fishery. It is shown that the widespread use of 

 deep trap nets in Lake Huron (the gear was fished much less extensively in Lake 

 Michigan) led to a multiplication of fishing intensity that raised production far beyond 

 a reasonable level and was responsible for the subsequent collapse of the fishery. 



