Fishery bulletin of the Fish and Wildlife Service - NOAA

342 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE
the four consecutive years, 1929-1932 (table 15), may well have contributed to the
sharp decline in abundance in 1933 (table 21). Similarly, in other districts the declines
in abundance that followed years of increased fishing intensity and high yields might
have been less severe had the fishery of the preceding years been less intensive. The
actual detection of the possible effects of high production on the abundance of whitefish
in later years is difficult, since in Lake Michigan as in Lake Huron a decline from
the peak of abnormal abundance was to be anticipated whether or not extensive overfishing
occurred. Furthermore^ the data for Lake Michigan do not provide the sharp
contrasts that made the presence and effects of overfishing in Lake Huron so easy to
detect. (Compare especially the annual fluctuations in the production and fishing
intensity in the various districts of the two lakes—figs. 5-10 for Lake Huron and
13-20 for Lake Michigan.)
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CALENDAR УЕЛИ
FIGURE 14,—Second district, M-2.
1933 1935
C A L C H O A O tf E A R
FIOVKI 15.—Third district, M-3.
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1933 I 9 J S
C A L E N D A R У E A R
FIQUEI 16.—Fourth district, M-4.
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