302 
BULLETIN OF THE BUREAU OF FISHERIES 
group from fish of greater age. Since the bulk of the II-group fish must lie above this 
depression it can be seen that their length distribution lies well within the range of 
efficiency of the 1%-inch mesh net. The fish taken in the 1%-ineh net are so few in 
number that they would have little effect in the determination of growth. 
SILVER LAKE 
The “old” gear was used in the collection of all the 1928 and 1930 samples of 
ciscoes from Silver Lake and for the first sample taken in 1931 (July 17). A gang of 
the “new” nets was used in taking the only other sample of this year in this lake 
(Aug. 22, 1931). In the sets of the old gear in 1930 and 1931 ciscoes were taken in 
1 y 2 - and 2-inch mesh nets only; in 1928 they were probably taken in the and 1 74- 
inch meshes also. In the new gear they occurred in the l}i~, 1 1%-, and 2-inch 
mesh nets. 
Table 74 shows the average length of fish taken in different mesh sizes and the 
effect of net selectivity on the determination of the average length of the various age 
groups of the 1930 collection (5 lifts of 1^-inch nets, 3 of 2-inch nets) while table 75 
gives similar information for the 2 lifts made in 1931. 
Table 74. — Effect of size of mesh of gill nets on the determination of the average lengths of the age groups 
of the Silver Lake cisco, 1930 collection 
[Sexes combined. Number of specimens in parentheses] 
Size of mesh 
Age group 
Average 
length 
II 
III 
IV 
V 
VI 

173 (7) 
178 (16) 
186 (9) 
182 (34) 
188 (24) 
190 (4) 
193 (20) 
198 (1) 
196 (2) 
186 (66) 
190 (64) 
173 (7) 
181 (25) 
183 (58) 
193 (25) 
197 (3) 
Table 75. — Effect of size of mesh of gill nets on the determination of the average lengths of the age groups 
of the Silver Lake cisco, 1931 collection 
[The data in the upper part of the table are based on a lift of the “old” nets, July 17. The data in the lower part are based on a 
lift of the ‘ ‘ new ” gear, Aug. 22. The grand average for the year includes a number of preserved fish for which no net records were 
available. Sexes combined. Number of specimens in parentheses] 
Size of mesh 
ltt inches - 
2 inches — 
Average — 
Hi inches - 
US inches 
l$i inches 
2 inches 
Average 
Grand average for 1931. 
Age group 
Average 
length 
I 
II 
III 
IV 
V 
VI 
VII 
143 (6) 
168 (5) 
174 (3) 
189 (3) 
173 (3) 
187 (5) 
163 (18) 
191 (29) 
192 (14) 
198 (5) 
143 (6) 
168 (5) 
182 (6) 
182 (8) 
192 (14) 
198 (5) 
141 (51) 
146 (6) 
172 (3) 
170 (6) 
174 (2) 
175 (3) 
176 (4) 
178 (22) 
174 (1) 
172 (1) 
173 (6) 
182 (25) 
184 (12) 
195 (2) 
187 (7) 
186 (23) 
190 (18) 
193 (4) 
192 (2) 
201 (1) 
146 (60) 
171 (30) 
183 (83) 
188 (37) 
142 (57) 
171 (11) 
177 (30) 
181 (44) 
188 (50) 
193 (6) 
201 (1) 
142 (66) 
171 (19) 
177 (61) 
183 (102) 
188 (108) 
194 (21) 
201 (1) 
The data in tables 74 and 75 show rather large differences in the average size of 
fish taken in nets of different sizes of mesh. Although the fish taken in the 2-inch- 
mesh net of the old gear in 1930 were only 4 millimeters longer than those taken in 
the 1%-inch net, the 1931 samples taken in the same gear showed a difference of 28 
millimeters, while the 2-inch-mesh net fish of the 1931 collection in the new gear 
had an average length 17 millimeters above the average for those from the 1%-inch 
net. A comparison with the Trout Lake and Muskellunge Lake data (tables 71 and 
72, fig. 11) shows that the selection of the nets is sharper in the Silver Lake cisco than 
