PROGRESS IN BIOLOGICAL INQUIRIES, 1939 61 
of various sizes of mesh, have been employed for a study of the life 
history of the kiyi by Drs. Deason and Hile. The bulk of the scale 
material has now been studied. Growth rate is very rapid during the 
first year for fish in all parts of the lake, and averages about 100 mm. 
The increment during the second year is less than half of the first- 
year increment, and “the growth rate decreases perceptibly during 
each of the later years of life. There appears to be an inverse rela- 
tionship between latitude and the rate of growth. <A slightly more 
rapid growth is indicated for the females ‘than for the males, The 
scale collections, obtained from unassorted samples of the commercial 
catches of different sizes of mesh, between 234 and 234 in., stretched 
measure, consisted of members of age-groups II to VIII. The best 
represented age groups were ITI, 1V, and V. The report will include 
also data on bathymetric distribution and on the occurrence of the 
kiyi in the different regions of Lake Michigan. 
COOPERATIVE INVESTIGATIONS OF WISCONSIN LAKES 
The Bureau continued to cooperate with the Wisconsin Geological 
and Natural History Survey in their limnological and fishery investi- 
gations of the lakes of northeastern Wisconsin by pr oviding a small 
amount of financial assistance. Those investigations, conducted un- 
der the direction of Drs. E. A. Birge and Chancey Juday, are con- 
cerned with the study of lony- term problems of theoretical and 
apphed limnology and fishery biology. 
Materials collected during the course of the cooperative investiga- 
tions, 1930-32, during which time Dr. Ralph Hile, of the Bureau, 
was assigned to that work, have formed the basis for two fish papers, 
both of which are now in press. 
Bathymetric distribution of fish—Records of fishing operations 
with gill nets were employed by Drs. Hile and Juday in a study of 
the vertical distribution of fish in summer in five northeastern Wis- 
consin lakes. Comparisons of data for different lakes revealed that 
the depth of water inhabited by a single species varies rather widely 
from one lake to another; that the relationship between size of fish 
and depth of water inhabited varies from lake to lake; and that 
different species that live at the same depths in one lake may inhabit 
different depths in another. The variations in the bathymetric dis- 
tribution of fish exhibited no clear-cut correlation with differences in 
temperature and the concentration of dissolved oxygen and free car- 
bon dioxide. This lack of correlation was not taken as evidence that, 
temperature and the concentration of dissolved gases are of little 
importance in determining the bathymetric distribution, but rather 
that other, undetermined factors may obscure the effects of physical- 
chemical conditions, 
Growth of the rock bass —The study by Dr. Hile of the growth 
of the rock bass, Ambloplites rupestris (Rafinesque), in northeastern 
Wisconsin placed emphasis on the problem of annual fluctuations in 
growth rate and the strength of year-classes. The growth rate of the 
Nebish Lake rock bass varied from a maximum of 20.6 percent above 
average in 1931, to a minimum of 15.2 percent below average in 1928. 
The year- classes ranged in strength from the phenomenonally rich 
241635—40——_5 
