The Productivity of Fish Food in Oneida Lake 103 



On the sandy clay bottom 37 unit areas were examined, 

 containinj^ 440 mollusks and 662 associated animals, or an 

 average of 11.89 mollusks and 17.89 associated animals per 

 unit area. With this average as a basis, the five acres of this 

 bottom contain 23,308,738 mollusks and 35,069,938 associated 

 animals, or a total animal population of 58,378,676.* Combin- 

 ing this result with the total population of the clay bottom we 

 have a total calculation of 843,601,080 animals on the 92 acres 

 of bottom in which clay is the chief material of the soil. A 

 comparison of life per unit area of the sand habitats with the 

 clay and sandy clay habitats shows that the clay bottom con- 

 tains 33 per cent less of animal life than the sand bottom 

 supports. The sandy clay bottom is 13 per cent richer in 

 animal life than the clay bottom (see figure 34 for the life of 

 the sandy clay unit). 



A study of Tables Nos. 19 and 20, in which the animals of 

 the clay and sandy clay bottoms are plotted, shows that on the 

 sandy clay bottom the mollusks form 39.9 per cent of the total 

 amount of life. Of the mollusks /hnnicola makes up 43.6 

 per cent and Planorhis parvus 24.7 per cent. These four sj)c- 

 cies represent a total of 68.4 per cent, the other 17 species 

 forming but 31.6 per cent of the total mass of individuals. 

 Among the associated animals, oligochaete worms make up 19 

 per cent, dipterous larvae 25.3 per cent, and crustaceans 43.3 

 per cent. Hyalella alone forms 21.4 per cent of the associated 

 animals. The characteristic species of the sandy clay bottom 

 are Amnicola and Planorhis parints among the mollusks and 

 Hyalella and chironomid larvse among the associated animals. 

 The Crustacea as a whole may be said to dominate, forming 

 43.3 per cent of the total number. The presence of filamentous 

 algse (CFdogoniiini, Clodophora, etc.) is here a large factor in 

 providing food and shelter for the great number of individuals 

 present (see Embody, '12, p. 4). 



* The computations for the sandy clay bottom fatma are as follows : 

 6,272,640X5 = 31,363,200 square inches in five acres ^ 16^ 1,960,200 

 unit areas in five acres; X 11. 8g moUusks per unit area = 23,308,738 

 mollusks. 1,960,200X17.89 associated animals per unit area = 

 35,069,938 + 23,308,738 = 58,378,676 total animal population. 



