WHITEFISH FISHERY OF LAKES HURON AND MICHIGAN 



373 



Michigan do not appear to vary according to the depth of the water. (The data for 

 deep-water lifts are too scanty to be reliable.) 



Although it cannot be said that deep-trap-net lifts contained large numbers of dead 

 whitefish, there is good evidence that pound-net lifts contained even fewer. Not one 

 dead whitefish was found in all the pound-net lifts observed in Lake Michigan. In Lake 

 Huron pound nets only 0.61 percent of the whitefish were dead (0.94 percent of the legal 

 fish and 0.45 percent of the illegal fish). The percentage of dead legal fish was rather 

 high, but the percentage of dead undersized fish was far below that for deep trap nets in 

 shallow water (80 feet and less). 



ESTIMATES OF THE PROBABLE DESTRUCTION OF ILLEGAL-SIZED 

 WHITEFISH IN CERTAIN LOCALITIES AND YEARS 



It may be stated that the percentage of undersized whitefish handled by the fisher- 

 men and destroyed in the lifting of pound nets and deep trap nets was small, although 

 that percentage was somewhat larger for deep trap nets than for pound nets. If we 

 define as "known destruction" the quantities of whitefish dead at the time the nets 

 were lifted (including dead gilled fish), the data of the preceding sections make pos- 

 sible the following estimates of the percentages of the undersized whitefish destroyed in 

 Lakes Huron and Michigan in pound nets and deep trap nuts of different sizes of mesh: 



These estimates, percentages of "known destruction," range from 2.40 to 3.80. To 

 the "known" destruction of undersized whitefish must be added the undetermined loss 

 that resulted from the death of bloated live fish (this loss could not have been much 

 greater than 1 percent — see table 44) and of fish killed or injured fatally during the 

 sorting of the catch. 



Despite the fact that the percentage of the undersized whitefish that was destroyed 

 in a single lift was relatively small, the total destruction during the entire season may 

 have been considerable, especially in those localities where the fishery was intensive and 

 young whitefish were abundant. It is of some interest, therefore, to have estimates of 

 the total number of undersized whitefish captured by pound nets and deep trap nets and 

 of the total "known" destruction in certain fishing areas (table 46). 



The estimates of the total number of young whitefish captured were based on the 

 known number of nets lifted (as determined from fishermen's reports) and the average 



Table 46. — Estimated numbers of illegal-sized whitefish captured by pound nets and deep trap nets in cer- 

 tain areas of Lakes Huron and Michigan in certain calendar years, and the estimated known destruction 

 (fish dead at time of lifting) of undersized whitefish 



