The Relation of Mollusks to Fish in Oneida Lake 311 
on the food of these animals. The fact of the change of 
food habits coincident with growth, first elaborated by 
Forbes, was clearly indicated by the examination of fishes 
of various ages, from infancy to maturity. Of the 41 species 
of fish in hie Take, 18 are mollusk-eaters, more or less, or 
about one-half. The Pumpkinseed consumes mollusks to the 
extent of 66 per cent., the Common Sucker 30 per cent., and 
the Yellow Perch 10 per cent. The fishes naturally divide 
themselves into types characteristic of certain feeding habits: 
as bottom-feeders, eating mollusks, insects and other animals 
inhabiting this region, and plankton-eaters, including nearly 
all young fish and some adults, taking the food near 
the surface or in the water above the bottom. This analysis 
may be carried further to include peculiarities of food, 
mollusk-eaters, insect-eaters, plankton-eaters,  fish-eaters, 
plant-eaters, mud-eaters, scavengers, and lastly those which 
are omnivorous, 
VI. A summary of our knowledge concerning the use 
of mollusks as food by fish shows that 46 out of 225 (about 
one-fifth) species of fresh-water fishes inhabiting New York 
and Illinois consume mollusks more or less, the ratios run- 
ning from 1 to 100 per cent., and being 31.50 per cent. for 
25 ‘of the most important food and game fishes. Several 
valuable food and game fishes, as the pike, feed upon other 
mollusk-eating fishes which are of themselves of little direct 
value, but which become economically valuable when they 
furnish food for these valuable food and game fishes. This 
indirect molluscan food supply forms 15 per cent. or about 
one-sixth of the food of the important fish-eating food and 
game fishes. 
VII. It was found that representatives of nearly all 
classes of animals prey upon mollusks, thus entering into 
competition with the mollusk-eating fishes for the food 
supply. It is noteworthy that many of these predatory 
animals, as insects and leeches, form the food of fishes, thus 
again indicating the interrelation between the different forms 
of life in the lake. 
