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BULLETIN OF THE BUREAU OF FISHERIES 
water inhabited by that species, the data do show that the cisco suffers the most 
rapid loss of condition with increase in length and shows the poorest average con- 
dition in the lake (Muskellunge) with the most eutrophic environment, while the 
most rapid gain in condition and the best average condition are found in Clear Lake 
with the most oligotrophic environment. While it is hardly to be inferred that a 
mere abundance of food causes loss of condition in the cisco or that a scarcity of 
food makes for better condition, it is quite probable that the cisco does not thrive 
in the physical and chemical conditions most conducive to a large production of 
food organisms. The eutrophic environment of Muskellunge Lake may, for example, 
force the cisco to live under such undesirable conditions of temperature and dis- 
solved oxygen that it fails to thrive even in the presence of abundant food, while 
in Clear Lake favorable physical and chemical conditions may make it possible for 
the cisco to reach the best of condition on a substantially smaller basic abundance of 
food. 
Average longevity and condition appear to be more closely correlated than 
average longevity and growth, for the four populations follow exactly the same order 
with respect to the two first-named characteristics. Such a relationship is logical. 
With particular reference to the populations whose K equations show negative ex- 
ponents, it appears probable that the progressive loss of condition with increase in 
length may bring the cisco to a point of emaciation beyond which survival is im- 
possible. Since length is a function of age the imposition of a limit on the length 
that can be attained places also a limit on age. It has been pointed out previously 
(p. 246) that in the Trout Lake cisco the few very old individuals taken had not 
followed the same length-weight relationship that held for the main body of the 
population. 
The relationship between individual condition and individual parasite infesta- 
tion is not known. The Clear Lake cisco with the lightest parasite infestation of 
any of the four populations is the population with the best condition. 
SEX RATIO 
The cisco population of the four lakes follow the same order with respect to 
growth in weight and the average relative abundance of males. In the section on 
sex ratio it was pointed out that the less viable males probably suffer greater mor- 
tality under adverse conditions that produce slow growth, and hence that the cor- 
relation between growth rate and sex ratio may be considered to result from the 
dependence of these two characteristics on the same environmental factors. 
GENERAL REMARKS 
The failure of certain of the growth relationships of the cisco to conform to 
generally accepted principles and theories suggests that, on the basis of our present 
knowledge, generalizations concerning these relationships are scarcely safe. A satis- 
factory understanding of the growth relationships of the cisco can be attained only 
after exhaustive studies into the biology of this form. Further, the great plasticity 
and adaptability of the cisco makes advisable the study of its biology in the greatest 
possible diversity of habitats. 
An illustration of the dangers of making generalizations concerning the growth 
and biology of the cisco is offered by the examination of the relationship between 
