MUSSELS OF CUMBERLAND RIVER AND TRIBUTARIES. 7 



GEOGRAPHIC DISTRmUTION OF THE MUSSELS. 

 CONTRAST BETWEEN TUE RIVER ABOVE AND BELOW THE FALLS. 



The Cumberland Falls establish a natural barrier, dividing the river 

 into an upper one-third and a lower two-thirds, between which there 

 can be practically no interchange of animal hfe, and very radical 

 differences appear in the mussel fauna. Above the falls only a very 

 few species of mussels are found, and these are considerably dwarfed. 

 Unio gihhosus is the only species in any abundance, and rarely one 

 may find examples of Lampsilis ovata, Alasmidonta minor, and Ano- 

 dontoides ferussaciana. This scarcity of species is as much due to the 

 fact that all the conditions are unfavorable (see p. 23) as it is to the 

 lack of intercourse past the falls, and in all probabiUty there would 

 be very httle profit in stocking the river above the falls with mussels. 

 Indeed we were told that some Lampsilis ovata were taken from below 

 the falls and transplanted to the river above about seven years ago, 

 with visible results, possibly, in the few dwarfed specimens of this 

 mussel now present in the upper river. 



In the river below the falls conditions are totally different. In 

 the very pool at the base of the falls were obtained 19 species of 

 mussels, all of them of normal size and perfectly healthy. And from 

 this point down to the Ohio every portion of the river bed that is at 

 aU suitable for mussels is fairly covered with them. 



Much of this part of the river has been thoroughly worked over 

 by agents of the button factories, and the location, extent, and pos- 

 sibiHties of the various beds are well known. Some clammers even 

 have a memorandum list of the beds, giving the percentages of usable 

 and useless shells in each. Many of these beds have been worked 

 for some time, a few of them as long as 10 years, and an immense 

 number of shells have been taken, as many as 200 to 300 tons from 

 some of them. But in spite of the great number of mussels taken 

 out, the river as a whole, according to general accounts, does not 

 show any marked depletion except in one or two restricted locaU- 

 ties. On the contrary, a comparison of many beds in the vicinity 

 of Cehna, Tenn., examined by Mr. Boepple in 1910 and again in 

 1911, showed a considerable increase. This was especially true of 

 beds situated above the silt in the back water from the various 

 lock dams. Such places seem peculiarly suited to rapid mussel 

 growth, and furnish thereby a valuable suggestion as to the best 

 locahties for artificial propagation. 



Of course the mussels that were too close to the dams, or that were 

 in the mouth of tributaries filled with back water from the dams, 

 would be killed by the increased deposit of silt, and the rise of 

 water from behind the dams makes it harder to secure the mussels. 



