Pearse—The Parasites of Lake Fishes. 
169 
Yahara Oconomowoc 
Fox 
Hyalella . 
2.0 
1.9 
Ostracods . 
... 0.2 
Cyclops ....... 
... + 
Leptodora ... 
... 2.9 
2.4 
Daphnia .. 
.. . 21.4 
0.4 
Cladoeera, unidentified. 
1.1 
Sphaeridae . 
... -f 
Snails ... 
20.9 
2.0 
Leeches . 
0.1 
16.6 
0.6 
Bryozoa . 
Plants . 
Silt and sediment. 
1.9 
3.3 
Unidentified . 
2.1 
4.0 
From these figures it appears that a 
diet of fishes. 
insects. 
Cray- 
fishes, snails, and leeches is associated with parasitic infection 
more than chironomid larvae and cladocerans, but the observations 
cover too limited a period to be of much significance. 
COMPARISON OF THE FISH PARASITES OP FIVE 
WISCONSIN LAKES 
As the study of the yellow perch in sixteen lakes had not given 
results of particular value, it was decided to study the parasites 
of all the fishes available in several different types of lakes. Ac¬ 
cording to this plan five Wisconsin lakes were studied intensively 
during the summers of 1919 and 1920. Accounts of the food and 
distribution of the fishes in these lakes have already been pub¬ 
lished (Pearse, 1921, 1921a). All the lakes were of considerable 
size and depth. Their general characteristics are given in table 5. 
Lake Geneva is deep, clear, and its deepest parts are without 
oxygen in summer. Mendota is deep, turbid and the water below 
8 to 12 meters is without oxygen for three months during summer 
and early autumn. Pepin is the shallowest of the lakes, but it has 
the greatest area of any lake except Michigan. Its temperature is 
nearly uniform from top to bottom and it forms a part of the 
Mississippi River. Green Lake is deep and has a small surface 
area; it is sharply stratified thermally but has plenty of oxygen at 
the bottom at all seasons. Lake Michigan is clear, cool, and of 
course, has a very large volume of water compared to the other 
lakes. In regard to “fertility,’^ as judged by the probable amount 
of food for fishes per unit of area, the lakes rank in about the 
following order: Mendota, Green, Geneva, Michigan, Pepin (Pearse, 
