374 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



number of undersized whitefish per lift (as determined from our observations in the 

 field). Estimates were made separately for large-mesh (4 inches and greater) and 

 small-mesh (less than 4 inches) nets and combined to obtain the totals listed in the 

 table. It was necessarily assumed that the relative numbers of large-mesh and small- 

 mesh nets in the general fishery were the same as those observed by our investigators 

 in the field. Estimates were made of the capture and destruction of illegal-sized 

 whitefish by deep trap nets in H-5 in both 1932 and 1933, although field observations 38 

 were made only in 1932. The computations for 1933 (based on the assumption that 

 the abundance of young whitefish and the relative numbers of large-mesh and small- 

 mesh nets were the same in that year as in 1932) were carried out merely to provide a 

 rough idea of the large numbers of whitefish that probably were handled during the 

 years of intensive fishing in southern Lake Huron. 



The estimated numbers of young whitefish handled by pound-net and deep-trap- 

 net fishermen in the various districts and years were large (130,000 to 616,000). The 

 estimated destruction, however, appeared to be relatively small (4,600 to 21,700). The 

 combination of the data for all districts and years indicates a loss of 2.8 percent of all 

 undersized whitefish taken in pound nets and of 3.4 percent of those captured by deep 

 trap nets. These figures should not be taken as indicative of the percentage loss of the 

 total population of undersized fish (of the sizes handled) as many fish may have 

 been captured more than once and others, doubtless, were not captured at all. 



Estimates were made also of the loss of small whitefish in the entire lakes (Michi- 

 gan waters) in 1932, the year of our most extensive field observations. The 1932 

 pound-net yield in districts H-2 to H-5, inclusive, amounted to 43.5 percent of the 

 catch of whitefish in pound nets in the entire lake. The "known" destruction of white- 

 fish by pound nets in these districts in 1932 amounted to 5,100 individuals (table 46). 

 If the average conditions of the pound-net fishery (abundance of young fish on the 

 grounds and relative numbers of large-mesh and small-mesh nets) in H-l and H-6 are 

 assumed to have been similar to those of the fishery in H-2 to H-5, the "known" de- 

 struction of undersized whitefish in the pound nets of all Michigan waters of Lake Huron 

 in 1932 can be calculated as 5,100/0.435 or 11,700 fish. Similarly, the deep trap nets 

 of districts H-2 to H-5 accounted for 93.8 percent of the total deep-trap-net catch 

 and for the estimated destruction of 20,600 young whitefish. The estimated "known" 

 destruction for all six districts was, therefore", 20,600/0.938 or 22,000 fish. The com- 

 bined "known" destruction of pound nets and deep trap nets in Lake Huron in 1932 was 

 33,700 whitefish. 



The same calculations for the Michigan waters of Lake Michigan showed that in 

 1932 districts M-2 and M-3 yielded 52.1 percent of the total catch of whitefish in pound 

 nets and 76.5 percent of the deep-trap-net production. These percentages applied to 

 the figures on "known" destruction in table 46 yielded the following estimates of the 

 loss of undersized whitefish in all eight districts: pound nets — 6,100; deep trap nets — 

 11,600; pound nets and deep trap nets — 17,700. 



The estimates of the "known" destruction of undersized whitefish by deep trap nets 

 in all Michigan waters of Lakes Huron and Michigan in 1932 (22,000 and 11,600 indi- 

 viduals, respectively) can not be termed large. If that gear was extremely harmful to 

 the stocks of small fish the loss must have occurred through the death of fish that were 

 killed or injured fatally in the sorting of the catch. 



The opinions of the fishermen concerning the ability of the whitefish to withstand 

 handling were found to vary widely. Some (particularly those who were opposed to the 

 use of deep trap nets) contended that whitefish are extremely delicate — that they are un- 

 able to survive removal from the water for even short periods of time and will die as the 

 result of the least amount of handling. Others (especially deep-trap-net fishermen) held 

 that the whitefish is exceptionally hardy — that with only reasonable care very few or none 

 at all are injured during the sorting of the catch. 



Data are not available to show which of the above diametrically opposite view- 

 points is the more nearly correct. However, the fact that 101 or 22.1 percent of 457 



M The pound-net fishery for whitefish was negligible in H-5 in 1932 and 1933 (appendix B). Our investigators observed no pound-net lifts in 

 this district. 



