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BULLETIN OF THE BUREAU OF FISHERIES 
13. The approximate date at which the season’s growth of the cisco is completed 
in each of the lakes is: Trout Lake, end of July; Muskellunge Lake, late August; 
Silver Lake, early September; Clear Lake, late September or early October. Growth 
probably begins in all four populations shortly after the disappearance of the ice at 
about the 1st of May. The data show that the length of the cisco’s growing season 
depends on the local conditions within each lake and not on the climatic conditions 
that are approximately the same for all four lakes. 
14. The bathymetric distribution of the cisco in middle and late summer is 
highly sensitive to conditions of temperature and dissolved oxygen concentration. 
A knowledge of the vertical distribution of the cisco is important in the comparison 
of the densities of the populations of different lakes. 
15. The order of the four lakes with respect to the density of their cisco popula- 
tions, from the minimum to the maximum, is: Clear Lake, Silver Lake, Muskellunge 
Lake, Trout Lake. 
16. The large differences observed in the relative abundance of the various year 
classes show that the degree of success of the hatch of the cisco in different calendar 
years is subject to a wide range of variation. Since the years that saw relatively 
successful or unsuccessful hatches of the cisco are not the same in different lakes, it 
must be concluded that the relative abundance of a particular year class depends 
(as does the length of the growing season) on the local conditions within each individ- 
ual lake, and not on general climatic conditions that would affect all lakes in the same 
manner. 
17. In the Clear Lake cisco sexual maturity appears to be general at the end of the 
second year of life. In the other populations the cisco is known to be mature at the 
end of the third year of life, while some, at least, mature in the second year. 
18. The order of the four lakes with respect to the sex ratio of the cisco populations 
(expressed as the number of females per 100 males), from minimum to maximum, is: 
Clear Lake, Silver Lake, Muskellunge Lake, Trout Lake. The differences among the 
populations with respect to the sex ratio depend on differences in the differential rates 
of mortality of the two sexes. 
19. The available data indicate a close connection between certain phases of the 
life history of the cisco and the nature of its animate and inanimate environment. 
20. The order of the four lakes with respect to the rate of growth of their cisco 
populations (in weight) is the same as their order with respect to the length of the 
cisco’s growing season, and the reverse of their order with respect to the density of 
their cisco populations. 
21. The observed differences in the length of the cisco’s growing season in different 
lakes cannot account entirely for the observed differences in growth rate, but probably 
serve only to accentuate differences that already exist. 
22. Suggested explanations of differences in the length of the cisco’s growing 
season in different lakes were: (1) That they may depend on differences from lake to 
lake in the nature of the plankton cycle, and (2) that the smaller spawners of slow- 
growing populations may begin the development of the gonads, preliminary to autumn 
spawning, earlier in the season than do the larger spawners of the rapidly growing 
populations. (The four lakes follow the same order with respect to growth rate, 
length of the growing season, and the average size of mature fish.) 
23. The correlation between density of population and growth rate may depend 
on differences in the severity of the competition for food, or upon the operation of a 
