AGE AND GROWTH OF THE CISCO 
217 
TREATMENT OF PRESERVED SPECIMENS AND RESULTING SHRINKAGE 
Part of the fish preserved for morphometric study were weighed and measured 
while fresh. These specimens were provided with individual, serially numbered tin 
tags. Other specimens to be preserved were divided into small groups which were 
wrapped in cheesecloth. Within each package was included a label bearing a record 
of date, locality, and usually of gear. The specimens were held in a 10-percent for- 
malin solution until the close of the season. Upon removal from the formalin solu- 
tion the fish were soaked in water about 4 days and then transferred permanently to 
a 70-percent solution of alcohol. 
Since the preserved specimens — most of which were not weighed and measured 
in the field — constituted a part of the material used for a study of growth, it was of 
some importance to know the extent of the shrinkage brought about by the preserving 
fluids. Data on this question were obtained from 99 ciscoes from Clear Lake and 
from 105 ciscoes from Muskellunge Lake, all taken in 1932. These fish were 
weighed and their lengths measured at the time of capture. The dates of capture 
for the Clear Lake specimens were July 12 to July 19; for those from Muskellunge 
Lake, July 28 and July 29. The individuals of both collections were reweighed 
and remeasured October 10 and October 11, 1932. At this time they had been in 
alcohol about 5 weeks. The measurements and weighing of both the fresh and pre- 
served material were made by the same method and by the same individual (Dr. 
Schneberger). 
The ratio between preserved length and fresh length was 1.000 : 1.019 for the 
Muskellunge Lake cisco. This value of the shrinkage factor agrees closely with the 
figure, 1.016, determined by Van Oosten (1929) for the Lake Huron herring. Since 
the populations from Silver Lake and Trout Lake do not have greatly dissimilar 
length ranges (approximately 125-200 millimeters) the shrinkage factor based on the 
Muskellunge ciscoes has been used in correcting for shrinkage the lengths of the pre- 
served specimens from these two lakes. 
In the Clear Lake cisco, where the length range is much greater, the relative 
amount of shrinkage was found to vary at different lengths. The lengths of pre- 
served specimens from this lake were corrected according to the following shrinkage 
factors: 
Length interval: 
350 
250-349 
150-249 
Shrinkage 
factor 
1.005 
1.010 
1.028 
Number of 
specimens 
16 
65 
18 
The shrinkage factors for weight were 1.181 for the Muskellunge Lake ciscoes 
and 1.144 for the Clear Lake ciscoes. However, the individual shrinkage in weight 
varied so widely that it was not considered valid to employ a weight shrinkage factor 
for the purpose of making individual corrections. Only those preserved specimens 
that were weighed when fresh were used for the study of growth in weight. 
PREPARATION AND EXAMINATION OF SCALE MATERIAL 
Scales were soaked in water and cleaned by means of a dissecting needle and a 
small camePs-hair brush. Three scales from each fish were mounted on a microscope 
slide in a gelatin-glycerin medium prepared according to a formula presented by Van 
Oosten (1929). No regenerated scales or scales with abnormal or irregular shape 
