AGE AND GROWTH OF THE CISCO 
265 
Table 46. — Age composition of the samples of the Muskellunge Lake cisco 
[The percentages are given in parentheses] 
Year of capture 
Age 
I 
II 
III 
IV 
1928 
19 (6. 8) 
252 (89. 7) 
10 (3.6) 
1929. 
1930 
17 (6.9) 
9 (1. 5) 
214 (87. 3) 
258 (41.9) 
14 (5.7) 
347 (55. 3) 
1931 - 
2 (0 3) 
The study of the age composition of the Silver Lake collections (table 47) reveals 
the presence of one year class (1926) which may be considered good and of one year 
class (1929) which may be considered poor. The 1926 year class was dominant in 
the collections of 2 of the 3 years, as the IV group of 1930 and as the V group of 1931. 
The scarcity of 1926 year class individuals as the II group in the 1928 collection can 
be explained on the basis of gear selectivity. The 1929 year class must be considered 
relatively poor because of its relative scarcity as the II group of the 1931 collections. 
This scarcity can hardly be the result of selection by gear as the individuals of the 
age groups on either side are more than three times as numerous. The great abun- 
dance of I-group fish in 1931 as compared with 1930 is the result of the introduction 
of smaller meshed nets in the first-named year. The lack of individual net records 
makes it impossible to determine the reason for the scarcity of I-group fish in 1928. 
However, the 1930 year class can safely be considered more abundant than the 1929 
year class. The 1924 year class which was dominant as the 1928 IV group may pos- 
sibly represent a good production year. 
Table 47. — Age composition of the samples of the Silver Lake cisco 
[The percentages are given in parentheses] 
Year of capture 
Age 
I 
II 
III 
IV 
V 
VI 
VII 
1928 
1 (0.7) 
9 (6. 7) 
46 (34. 1) 
69 (51. 1) 
10 (7.4) 
1929 
1930 
7 (5.9) 
19 (5. 0) 
25 (21. 2) 
61 (16. 1) 
58 (49. 2) 
102 (27. 0) 
25 (21. 2) 
108 (28. 6) 
3 (2. 5) 
21 (5. 6) 
1931 
66 (17. 5) 
1 (0. 3) 
The Clear Lake samples (table 48) present much more definite and consistent 
indications of the presence of successful and unsuccessful year classes than were 
found in the other three lakes. Figure 5 shows graphically the year class composition 
for the 1931 and 1932 collections. The agreement between the 2 years in the relative 
abundance of the different year classes is close. Since the individuals of each year 
class were a year older in 1932 than in 1931, and consequently of a different size range, 
this close agreement between the year class composition of the 2 years’ collections 
may be taken as strong evidence for a high degree of reliability of the Clear Lake 
samples both as to year class and as to age composition. 
