WHITEFISH FISHERY OF LAKES HURON AND MICHIGAN 347 



4 of the 7 years in which abundance was less than 100. The circumstance that fishing 

 intensity was so much below the maximum in the years in which the abundance of the 

 Lake Huron whitefish was above average should not be taken to indicate that the Lake 

 Huron fishermen were less prompt than the Lake Michigan fishermen to take advantage 

 of this abnormal abundance. In fact, the fishing intensity rose sharply in Lake Huron 

 as the increase from 46 in 1929 to 100 in 1931 shows. The 1931 intensity was more than 

 twice that of 2 years earlier. The fishing intensity in these early years of the 11-year 

 period is represented by small percentages simply because the excessive use of deep 

 trap nets led to a 1929-1939 average of fishing intensity that was far above a level that 

 could reasonably be considered normal. It is doubtful whether without the use of deep 

 trap nets the intensity would have reached the high level recorded for 1932, and much 

 less have risen to still higher levels and maintained itself above the 1932 intensity until 

 1936. These considerations serve to bring out again the immensity of the overfishing 

 that occurred in Lake Huron. 



From the mass of evidence obtained from the statistical data of the whitefish 

 fisheries of Lakes Huron and Michigan the following general conclusions may be drawn. 



Lake Huron. — The deep-trap-net fishery, expansion of which was fostered by an 

 abnormal abundance of whitefish that reached its peak in 1930-1931, was the primary 

 cause of excessive overfishing in Lake Huron. This overfishing led to the collapse of 

 the whitefish fishery in central and southern Lake Huron and contributed to the 

 decline of the fishery in the northern part of the lake. 



Lake Michigan. — A similar abnormal abundance of whitefish in Lake Michigan, 

 with the peak probably in 1929, was accompanied by increases in fishing intensity 

 and production. Although this intensive fishery may have affected adversely the 

 later abundance of whitefish, there is no evidence of overfishing comparable to that 

 which occurred in Lake Huron. The decline of the whitefish in Lake Michigan was 

 pronounced but not disastrous. The difference in the course of the fishery in the two 

 lakes can be attributed to the relatively limited use of deep trap nets in Lake Michigan. 



