Fishery bulletin of the Fish and Wildlife Service - NOAA

WHITEFISH FISHERY OF LAKES HURON AND MICHIGAN 339
Michigan fishermen were able to abolish the net from their waters by law) ; (3) the
summer aggregation of whitefish occurs in shallower water in Lake Michigan than in
Lake Huron and hence the Lake Michigan fish never moved beyond the reach of pound
nets to the same degree as did those in Lake Huron; (4) the deep-water population of
whitefish available to the deep trap nets was less dense in Lake Michigan than in
Lake Huron, hence in contrast to the situation in Lake Huron the deep-trap-net lifts
did not always average much larger than those of the pound nets. (See, for example,
M-l and M-2 for 1931, table 17.)
Although the deep trap net usually took more whitefish per lift than did the pound
net in Lake Michigan, and from this point of view may be considered to have been very
effective and successful, in no district of the lake did the catch per lift of deep trap
nets approaclj the level that it attained in the four southerly districts of Lake
Huron (tables 11 and 17). The average catch per lift of deep trap nets in Lake Michigan
reached values of 257.5 pounds in M-2 in 1932 and 184.4 pounds in the same district
in 1931. Operations were limited, however, in M-2. In M-l and M-3, where deeptrap-net
operations were more extensive, the greatest average catches per lift were 131.7
pounds (M-l in 1930) and 164.9 pounds (M-3 in 1932). These values were far below
the greatest averages in the districts of central and southern Lake Huron (402.5 to
476.1 pounds per lift), but compared favorably with the maxima in northern Lake
Huron (167.7 pounds per lift in H-l in 1930; 141.9 pounds per lift in H-2 in 1930).
The deep trap net was relatively unsuccessful in southern Lake Michigan also, for the
only significant operations with the gear (M-7 in 1934) yielded an average of 118.2
pounds of whitefish per lift.
To be sure, the deep trap net was introduced into northern Lake Michigan after
the peak of abundance of the whitefish had passed. The examination of the abundance
percentages of table. 21 suggests that if this gear had been fished in 1929, the
year of high abundance, the average catch per lift in that year most probably would
have exceeded the highest yields listed in table 17 JOT deep trap nets in each of the
northern districts. On the other hand, abundance percentages may not validly serve
as an exact index to the average size of a lift since the fluctuations in the catch per
lift of this gear did not always correspond with those in abundance subsequent to 1929.
For example, the average catch per lift of deep trap nets in M-l decreased in 1931 and
increased in 1932 despite the fact that abundance remained practically unchanged in
1931 and fell in 1932. Again, the highest yield (257.5 pounds per lift) of the northern
area occurred in a district (M-2) when abundance was normal (1932).
As the average deep-trap-net lifts were small in comparison with those of central
and southern Lake Huron irrespective of how much abundance was.above average;
the conclusion appears valid that in northern Lake Michigan as in northern Lake
Huron the deep trap net was far less successful than it was in central and southern
Lake Huron.
The maximum and 1939 percentages of production, fishing intensity, and abundance
in table 18 have been computed with respect to average conditions in 1929-1939.
The corresponding estimates for Lake Huron (table 7) were made with reference to
TABLE 18.—Maximum and 1939 production and abundance of whitefish and maximum and 1939 fishing
intensity for whitefish
District
M-l
M-2
M-3 - ---
M-4
M-ï
М-в
M-7
M-8
[Eipressed as percentages of the average 1929-1939 values in each statistical district of Lake Michigan]
Year of
maximum
production
1931
1930
1930
1931
1931
1931
1930
1934
Production
Maximum
227
184
230
148
183
345
433
235
1939
45
28
40
58
31 71
20
Year of
maximum
intensity
1931
1932
1930
1931
1932
1931
1930
1934
Intensity
Maximum
198
180
159
127
129
242
271
•218
1939
85
41
65
88
77
187
34
Year of
maximum
abundance
1929
1929
1929
1929
1931
1930
1930
1929
Abundance
Maximum
170
189
166
127
162
209
222
161
1939
81
89
67
88
41
53
33
71