The Relation of Mollusks to Fish in Oneida Lake | 155 
TABLE NO. 10. FOOD OF THE COMMON PERCH SHOWING 
VARIATION WITH AGE (AFTER FORBES). 
1. Infancy. 2. Youth. 3. Adult. 
Entomostraca............ Entomostraca at first. .....| Mollusks. 
al erOMOIDLera om. 3.0. ..|, INSCCUS a .i7.2 -e eiern eas ogs hey Crawfish. 
PM evOMMIMPCMerAl os 42) .\ec ces cose ee lae eee eee ea: | Insects. 
| Fishes (few). 
| 
Many carnivorous species pass through three periods, each 
marked by the presence of a particular kind of organism, as: 
1. Entomostraea. 2. Insects. 3. Fishes. 
1. Entomostraca. 2. Insects. 3. Mollusks. 
Catfishes live on plankton when young and when adult are 
omnivorous. Black Bass eat plankton when young and fishes 
and crawfish when adult. Entomostraca and the larvee of 
minute flies form 75 per cent. of the food of the majority 
of young’ fishes. 
The large clams (Unionidew) form an unimportant element 
of the available food supply, being used by but few species 
of fish, notably the catfishes (Forbes, 1888, b, p. 481; Adams, 
1892, p. 127); but the gastropods and small clams 
(Spheriide) form a large percentage of the total food chosen 
by a considerable number of fish families. In a few species 
the small bivalve Sphwrium forms a large part of the food, 
as shown below: 
pMckeri family) tise oF. oo 4 fase oe Cl. ds. Pole lades de 29 per cent. 
Dootishes. CFM ND TPE, Smee a cyan ope 19 per cent. 
EULVER CAL Ds ((OGTDtOMES) [aw sie.cth Misr so «kes ate 1a oi 25 per cent. 
It is noteworthy that in a number of families the mouth is 
especially modified or adapted for feeding upon mollusks, 
examples being eatfishes, suckers, the Sheepshead and the 
small-mouthed sunfishes. 
