Pearse—The Parasites of Lake Fishes. 
183 
Ergasilus centharchidium Wright 
In Lake Michigan on the gills of the rock bass. 
Pisces 
Icthyomyzon concolor (Kirtland) 
This lamprey was taken in Lake Pepin on a spoonbill. 
Discussion and Conclusions 
A summary of the parasites found in the five lakes studied is 
given in table 4. The writer had expected to publish six additional 
tables giving the number of fishes infected and total average in¬ 
fection for each parasite but the space available will not permit 
this. Those interested in such detailed information may obtain 
it by letter. Lake Mendota in all respects contained the smallest 
number of parasites—the average number in each fish being 2.0; 
the average number of species of fishes each parasite infected, 4.7; 
and the average number of individual fishes infected by each para¬ 
site, 1.4. Lake Pepin had the largest average number of parasites 
per fish (5.0); Green Lake the largest average number of species 
of fishes infected by each species of parasite (8.1); and Lake Gen¬ 
eva the largest average number of individuals infected by each 
parasite (2.2). 
The lakes with the widest range of territory and opportunity 
for fishes to invade the greatest variety of habitats have the high¬ 
est average infection per fish (Pepin, 5.0; Michigan, 3.9). How¬ 
ever, the fishes in Pepin, with its shifting, sandy bottom and lack 
of thermal stratification, have 22 per cent more parasites than 
Michigan, with its soft mud bottom and cold deeper water. The 
two lakes with the largest average number of species of fishes in¬ 
fected per species of parasite include the one with a large number 
of species of fishes and habitats '(Pepin, 8.1) and the one with the 
smallest number of species of fishes and the least variety of habi¬ 
tats (Geneva, 6.6). The lakes having the largest number of in¬ 
dividuals infected by each parasite include one with the least range 
and variety of habitats (Geneva, 2.2), one with wide range and 
variety of habitats {Michigan, 2.1), and one in which there was 
little variety in the shore habitats and a sharp distinction between 
deep and shallow water habitats (Green, 2.1). 
