234 
BULLETIN OF THE BUREAU OF FISHERIES 
Wilier (1929) called attention to the fact that certain fishes can be said to possess 
a typical species growth curve that retains a characteristic form regardless of the 
extent to which external factors influence the actual amount of growth. With re- 
spect to growth in length the cisco seems to possess such a species growth curve. 
It will be noticed in table 19 that the populations showing the greatest (Clear 
Lake, Indian Village Lakes) and the least (Trout Lake) amount of growth are found 
in small, inland lakes. Such a situation might be expected in view of the greater 
diversity of habitat furnished by the smaller bodies of water. The growth in the 
different populations cannot be classified according to latitude or region, but rather, 
the differences in growth seem to depend upon purely local conditions within the indi- 
vidual lake or possibly upon the genetic make-up of the local stock. 
A population showing a greater amount of growth in length than another does 
not necessarily show a greater amount of growth in weight. Two examples will 
illustrate this situation. (See tables 19 and 20.) At all ages beyond the seventh 
year the Oconomowoc Lake cisco is longer than either the males or females of the 
Clear Lake cisco, and yet at all ages the weights of the Oconomowoc fish are less 
than those of the Clear Lake fish of corresponding age. Secondly, at the age of 7 
years the weights of the Clear Lake and the Indian Village Lakes ciscoes are approxi- 
mately equivalent. At the same time the length of the Indian Village Lakes fish at 
the age of 7 years is greater than that attained by the Clear Lake 9 males in the 
ninth year and equal to the length reached by the Clear Lake females in the tenth 
or eleventh year. These discrepancies between growth in length and growth in weight 
find their origin in the different length- weight relationships in the various populations. 
Populations may differ both as to general body form itself and as to the manner of 
change of form with increase in length. 
RANGE OF LENGTH IN INDIVIDUAL AGE GROUPS; MAXIMUM LENGTH 
AND WEIGHT 
Tables 21 to 25 show for the four lakes under consideration here the length 
distribution of the different age groups in each year’s collection. On the whole, 
length is a poor index of age. The amount of overlap between consecutive age groups 
is so great that in most instances a fish of a given length might have any of several 
different ages. This is particularly evident in the Trout Lake data of table 21. 
In the rapidly growing Clear Lake population, however, the positions of both sexes 
of the first three age groups (I, II, and III) stand out clearly in the length frequencies. 
In the 1931 Silver Lake collection the I group is well separated from the remainder 
of the sample. The Muskellunge Lake collection of 1931 shows a fairly distinct 
separation of the II and III groups, but a greater abundance of other age groups in 
the collections of this year might have obscured this division. 
9 The average lengths of the Clear Lake fish measured at the time of capture were: IX group, male, 355 millimeters; X group 
female, 377 millimeters; XI group, female, 378 millimeters. 
