Fishery bulletin of the Fish and Wildlife Service - NOAA

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.