16 College of Forestry 



OXEIDA LAKE SHELLFISH 



The class of animals known as mollusks or shellfish (snails 

 and clams) are widely distributed and in many lakes and 

 rivers form a large and conspicuous part of the animal popu- 

 lation. Though popularly considered of little value except 

 as curiosities, this class of animals is of real economic 

 importance and value. On the Mississippi river, and other 

 streams of the Central West, the clams or mussels are sys- 

 tematically sought for their shells, from which much of the 

 pearl button material of commerce is obtained. In Illinois 

 and Iowa there are many factories which manufacture pearl 

 buttons and depend upon these clams for their raw material, 

 and the fishing of these shells furnishes occupation for many 

 men. Ixeceiitly, the supply of mussels has been threatened 

 with exhaustion owing to the unbusiness-like methods of fish- 

 ing and to conserve these animals the United States Bureau 

 of Fisheries has established, in part, a laboratory at Fair- 

 port, Iowa, for the study and artificial propagation of these 

 mussels. In addition to their shells the clams have fur- 

 nished many pearls of great beauty and large value. The 

 clams are usually obtained by means of a crowfoot dredge 

 which is a long bar of iron to which are fastened a number 

 of ropes bearing several four-pronged hooks made of heavy 

 wire. A fisherman's boat rigged up with two of these dredges 

 is an interesting sight (Fig. 5). 



The shellfish of Oiieitla Lake, however, are at present of no 

 particular value for the manufacture of pearl buttons, nor 

 do they, as far as known, afford pearls of value. They do, 

 however, form a part of the food of such fish as the Channel 

 Cat, as well as of such mammals as the Muskrat, Mink and 

 Otter. 



One of the most interesting and important discoveries 

 brought out in the investigations is that the shellfish or mol- 

 lusks greatly outnumber in individuals all of the other 

 (macroscopic) kinds of invertebrate animals living on the 

 bottom. In the quantitative computations to be described 

 later, it was estimated, 011 the basis of counting the animals 



