AGE AND GROWTH OF THE CISCO, LEUCICHTHYS ARTED1 
(LE SUEUR), IN THE LAKES OF THE NORTHEASTERN 
HIGHLANDS, WISCONSIN 1 
* 
By Ralph Hile, Ph. D., Assistant Aquatic Biologist, U. S. Bureau of Fisheries 
«3t 
CONTENTS 
Page 
Introduction 212 
Acknowledgments 214 
Materials 214 
Methods 215 
Gear used in collecting 215 
Methods of fishing 215 
Field data recorded for individual 
specimens 216 
Treatment of preserved specimens 
and resulting shrinkage 217 
Preparation and examination of scale 
material 217 
Miscellaneous considerations 218 
The scale method 218 
Assessment of age and calculation of 
growth 218 
Lee’s phenomenon in the Silver Lake 
cisco 222 
Possible causes of Lee’s phenomenon 
in the Silver Lake cisco 224 
Selection by gear 224 
Selection due to dissimilar dis- 
tribution within the lake 
of the various elements of the 
population 224 
Selection due to differential mor- 
tality, correlated with growth 
rate 225 
Other possible causes 225 
General growth curves for the Trout Lake, 
Muskellunge Lake, Silver Lake, and 
Clear Lake cisco populations 226 
Growth in length 226 
Growth in weight 230 
Comparison of the growth of the Trout 
Lake, Muskellunge Lake, Silver Lake, 
and Clear Lake cisco populations with 
that of cisco populations in other re- 
gions 232 
Range of length in individual age groups; 
maximum length and weight 234 
Page 
Condition and the relationship between 
length and weight 237 
Length of growing season 249 
Relationship between density of popula- 
tion and rate of growth 253 
Age composition of the samples and the 
relative abundance of year classes 263 
Age at maturity and sex ratio 267 
Annual increments of growth 271 
Variation in the amount of growth in 
different calendar years 271 
Bimodality in the calculated growth 
for the first year of life 280 
Growth compensation 282 
Growth relationships in the Trout Lake, 
Muskellunge Lake, Silver Lake, and 
Clear Lake cisco populations 286 
Physical-chemical factors 287 
Density of population 288 
Length of the growing season 288 
Parasitization 289 
Condition 289 
Sex ratio 292 
General remarks 292 
Fishes associated with the cisco 293 
Selective action of gill nets 294 
Review of previous investigations 294 
Selective action of gill nets used in 
collecting samples of ciscoes from 
Trout Lake, Muskellunge Lake, 
Silver Lake, and Clear Lake 298 
Trout Lake 298 
Muskellunge Lake 300 
Silver Lake 302 
Clear Lake 304 
Relative abundance of age 
groups in gill net samples 305 
General conclusions 306 
Summary 306 
Bibliography 310 
Appendix A. Growth of the cisco in Alle- 
quash and Tomahawk Lakes 316 
1 Bulletin No. 19. Approved for publication, July 31, 1938. 
211 
