The Prodnct'n'ity of Fish Food ui Oneida Lake 137 



plant. Eight plants occupied an area eight inches square (64 

 square inches) and the i)opulation was therefore 61.28 per 

 64 s(|uare inch unit. Water willow (Dianihera americana) 

 occurs in patches over the shoal area between the two islands 

 and it is difficult without measuring each patch to estimate 

 the total area covered by this plant. It is safe to estimate an 

 area of 5,000 square feet which would indicate the total 

 Bythinia population to be 689,400. It is probably much greate ■ 

 than this. 



It is to be noted that on the sand bottoms Bythinia, Aninicola 

 and Valvata iricarinata are the characteristic species of mol- 

 lusks. Of the associated animals, HyaleUa knickerhockeri, 

 chironomid larvae, and Eurycercus IcmellGtns are character- 

 istic. The great preponderance of mollusks over associated 

 animals (the latter being but 37.8 percent) in number of indi- 

 viduals is noteworthy (see Table No. 34 for the data bearing 

 on these sand habitats). 



Shoal North of Dunham Island (Table No. 35, Habitat 

 No. V). North of the west point of Dunham Island there is 

 a large shoal on which the water varies from a foot to three 

 feet deep, the bottom being very bouldery. This shoal is 

 upwards of 1,320 feet (a quarter of a mile) long and 200 feet 

 wide and contains about 264,000 square feet. Animals were 

 collected from two boulders and consisted of 55 mollusks and 

 237 associated animals or an average of 27.5 mollusks and 

 1 18.5 associated animals, a total population per unit of 146 

 individuals (see fig. 43). These figures indicate that the 

 population of this shoal may be 33,650,897 mollusks and 

 145,004,776 associated animals, a total estimated population 

 of 178,655,673.* The notable features of this locality are 

 the small ratio of mollusks to associated animals (18.9 per- 

 cent), the characteristic molluscan species being Galba, Pla- 

 norbis parvus, and Aninicola bakeriana nimia, and the large 

 number of HyaleUa among the associated animals. This shoal 



* The computation is : 264,000 square feet X 144 square inches = 

 38,016,000 square inches, -^ 30.25 (average area of boulder) = 1,223,669 

 unit areas, X 27.50 mollusks = 33,650,897 mollusks and X 118.50 asso- 

 ciated animals = 145,004,776 associated animals, the total estimated 

 population being the sum of these two results or 178,655,673 individuals. 



