286 
BULLETIN OF THE BUREAU OF FISHERIES 
year, and can within a single season change the length distribution of the group 
from a bimodal to a unimodal condition. 
(3) When the length distribution at the end of the first year of life is unimodal 
and the dispersion small, individual length at the end of the first year of life exerts 
more effect on individual length at the end of the second year of life, than the amount 
of growth during the first year of life exerts on the amount of growth during the 
second year of life. (In the II group the positive correlation of Lj and L 2 is greater 
than the negative correlation between Li and AL^) In the group with the greater 
dispersion and the bimodal distribution of lengths at the end of the first year of life 
the situation is reversed, that is, there is a closer connection between the amount 
of growth during the first year of life and the amount of growth during the second 
year of life than there exists between the length at the end of the first year and the 
length at the end of the second year. (In the III group the negative correlation 
between L x and ALj is greater than the positive correlation between Li and L 2 .) 
(4) In spite of the growth compensation that occurs there is a tendency for the 
individual to hold throughout life a part of any advantage in length which it may hold 
at the end of the first year of existence. Compensation reduces individual advantage 
in length, but does not obliterate it (positive correlation in both groups between 
L! and L T ). 
GROWTH RELATIONSHIPS IN THE TROUT LAKE, MUSKELLUNGE LAKE, 
SILVER LAKE, AND CLEAR LAKE CISCO POPULATIONS 
Throughout the preceding sections attention has been called repeatedly to the 
order in which the cisco populations of the four lakes arrange themselves with respect 
to certain characteristics such as growth rate, sex ratio, condition, and the like. In 
view of the apparent high degree of correspondence among certain of these orders 
of arrangement it is considered advisable to present the data concerning them in a 
summarized form, together with a brief discussion and review of the possible signifi- 
cance of the observed correlations. Table 68 shows that arrangement of the lakes 
with respect to the amount of bound carbon dioxide in their waters and to the amount 
of organic matter in the plankton, and also with respect to certain phases of the life 
history of the cisco. Although these data demonstrate a close dependence of certain 
phases in the life history of the cisco on the conditions of its animate and inanimate 
environment, as will appear in the following discussion, any attempt to describe these 
relationships in precise terms of cause and effect meets with serious difficulty. 
Table 68. — Order of the 1+ lakes with respect to the concentration of bound C0 2 and the abundance of 
organic matter in the surface plankton, and also with respect to certain phases of the life history 
of the cisco 
Lakes 
Item 
Clear 
Muskel- 
lunge 
Silver 
Trout 
Growth in length _ _ __ 
1 
2 
3 
4 
Growth in weight _ __ _ _ 
1 
3 
2 
4 
Bound COa in water _ . .. __ _ __ 
4 
3 
2 
1 
Density of population. .... 
4 
2 
3 
1 
Length of growing season - 
1 
3 
2 
4 
Sex ratio (females per 100 males)... ... .. . 
4 
2 
3 
1 
Organic matter in plankton 
4 
1 
3 
2 
Condition ( K). __ . 
I 
4 
2 
3 
Average length of life. 
1 
4 
2 
3 
