PROGRESS IN BIOLOGICAL INQUIRIES, 1921. / 13 
University of Michigan. The deep-water forms, as the blackfin 
(Leucichthys nigripimnis), were found to feed almost exclusively 
upon the crustacean Mysis relicta, probably the only available food. 
The deep-water race of the bloater (Leucichthys hoyi) feeds chiefly 
on Mysis, while a 30-fathom race eats for the most part another lake 
crustacean, Pontoporeia hoyi. The food of the shallow-water forms 
is much more varied. The pilot or menominee (Prosopium quadri- 
laterale) is strictly a bottom feeder, subsisting on mollusks, insect 
larvee, crayfishes, ete. The whitefish (Coregonus clupeaformis) is 
also a bottom feeder, but its food is, on the average, not so coarse as 
that of the pilot, consisting largely of insect larvae, as those of the 
mayflies Hexagenia and Ephemera. The lake herring feeds in part 
upon the same animals, in part upon the minute Crustacea of the 
plankton. In reference to their available food supply the deep- 
water forms are absolutely competitive (more so perhaps than any 
other group of fishes), while the shallow-water forms are only in part 
competitive. It is probable, however, in view of the former greater 
abundance of these fishes, that sufficient food exists in the lakes to 
support a larger population of all the species of whitefishes. 
FISHES OF WISCONSIN LAKES. 
The food and distribution of the fishes in certain Wisconsin lakes 
have been studied by Dr. A. S. Pearse.t The results indicate that 
in summer fishes are generally more abundant as conditions ap- 
proach those in swamps and are fewest when the environment is 
most like that in rivers. When food is present in quantity and when 
other conditions are favorable, there are more fishes per unit area 
in certain inland lakes than in the Mississippi River or in Lake 
Michigan. Lakes produce considerable food supplies within them- 
selves, while rivers are more dependent on swamps, ponds, and other 
tributaries. The factors of importance in limiting the distribution 
of fishes are discussed (shores, turbidity, depth, bottom, height of 
water, currents, etc.). An abundant supply of food and vegetation 
permits many fishes to exist in a lake, but other favorable conditions 
must be present in order that they may grow to large size. 
A statistical study of the infection of fishes by parasites has been 
made, the Mississippi and St. Lawrence drainage systems being 
compared, and various types of lakes studied. The results are now 
being tabulated and will soon be ready for publication. A short 
paper on the habits of the mud puppy, in which its relations to fishes 
are discussed, has been published.® 
In order to secure information on the rate of growth of cotd- 
blooded animals in natural] conditions, attempts are being made to 
recover the fishes and turtles tagged and released in Lake Mendota 
during the summer of 1919. Some specimens have already been 
secured. 
Studies on the metabolism of fishes are being continued. In this 
connection quantitative analyses are being made to show the water, 
ash, nitrogen, and ether extractives of fishes at various stages of 
growth. 
4Pearse, A. §8.: The Distribution and Food of the Fishes of Three Wisconsin Lakes in 
Summer. University of Wisconsin Studies in Science, No. 3, June, 1921, 60 p. Madison. 
5 Pearse, A. S.: Habits of the Mud-Puppy Necturus, an Enemy of Food Fishes. Bureau 
of Fisheries, Economic Circular No. 49, issued May 16, 1921, 8 p. Washington. 
