The Relation of Shellfish to Fish in Oneida Lake 17 



on many small sample areas, that the shellfish of Lower South 

 Bay and vicinity numbered 4,70-i million individuals, and 

 that the other associated animals numbered 3,062 million 

 individuals. The shellfish, therefore, are 30 per. cent greater 

 in number of individuals, showing that the shellfish are a 

 very important group of aquatic animals. 



Shellfish are mostly flesh producers, eating plant tissue 

 and plant debris, which is thus converted into animal tissue 

 which can be used by fish as food. The large clams or mus- 

 sels eat minute plants called diatoms and desmids, besides 

 the small particles of partly disintegrated vegetable matter 

 floating in the water, which the Danish naturalist, Dr. Peter- 

 sen, has called " dust-fine detritus.'*' Some small animals, 

 like the protozoans, are also included in the food. 



As just stated, snails (Fig. 6) are for the most part vege- 

 tarians, feeding upon algse and the soft tissues of plants, usu- 

 ally the outer part or epidermis. Snails may be frequently seen 

 browsing over the rocks which are covered with long strings 

 of green algae (filamentous alga?) much as cows browse over 

 a pasture. The peculiar rasping file-like tongue is covered 

 with many hundred minute teeth which enable the animal 

 to scrape off the algse and to cut, with the aid of a horny jaw, 

 the soft covering of larger plants. Only a very few snails 

 are carnivorous and these include for the most part the pond 

 snails or Lymncea. Some of these have been known to eat 

 other snails, leeches, and small fish as well as other dead 

 animals, and they may thus be regarded in a measure as 

 useful scavengers. Careful records have shown that as many 

 as thirteen different kinds of plants in Oneida Lake are used 

 by snails as a food supply, and twenty-two kinds of snails 

 were observed to use these plants for food. A very few snails 

 seem to prefer dead or decaying vegetation, as the little 

 limpet snails, Ancylus, but the majority of snails prefer 

 living plant food. 



Of the 197 species of fresh-water shellfish listed as living 

 in the State of New York, 92, or nearly one-half of the 

 species inhabiting the State, have been collected from Oneida 

 Lake. This number of species is believed to be greater than 



