292 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
horns” of yood (j utility, the last-iitimed constituting about 10 per cent of the mussels 
adapted for button-making. There is no fishing now carried ou in these streams, 
although there was a little six years ago. It does not itay to ship the shells, and 
there is no loctil demand. In the Skunk and Des Moines rivers there are some shells 
that might be utilized, but they arc not sufficiently abundant to maintain a large 
factory. Among others there are small, brittle “muckets” of little value, a few 
desirable “ pocketbooks” and “sand shells,” and some very good medium-sized “deer- 
horns.” lu Rock River, Illinois, there is reported an enormous growth of “muckets” 
which are not utilized. 
A number of animals prey on the mussels, among them the muskrat, the mink, 
and the raccoon, the first named being especially destructive. Catfish are also said 
to eat mussels. Hogs are known to be very injurious in some parts of the country. 
Physical causes are undoubtedly responsible for extensive destruction of mussels. 
During freshets mud and sand are deposited on the beds and bury the mussels. 
Sldfting sand bars are also known to cover up beds. The fishermen sometimes find 
extensive beds of dead shells which appear to have recently been uncovered by the 
current. During freshets, when the streams find new channels, many mussels are 
carried from their beds and left dry when the water subsides. Droughts also are 
liable to expose mussel beds and cause much destruction. 
Pollution of the water by refuse from cities and manufacturing establishments is 
perhaps the most serious menace to the mussel beds, next to the operations of the 
fishermen. Certain kinds of refuse are very destructive and are capable of killing 
practically every innssel with which they come in contact. 
Pishermen and button-makers report a considerable i)ercentage of “niggerheads” 
with the beaks portly gone, the remaining iiortion being softened and easily split 
into lainime. Accompanying this condition there is often a softening of the other 
parts of the shell in spots. Only the lai'ger (older) shells are thus affected, and it 
appears to represent a natural decay due to age. Buttons made from such a shell are 
soft, and are apt to split up into layers in the course of manufacture. 
For much interesting information concerning the habits, spawming, mode of dis- 
persal in the streams, rate of growth, etc., of the mussels, the paper of Mr. Simpson 
should be consulted. 
THE MUSSEL FISHERY. 
THE FISHERMEN. 
The mussel fishermen in the region under consideration are mostly people who 
have been engaged in other branches of fishing, or wdio, as boatmen, etc., are familiar 
w'itli the river. Many of them depend on mussel fishing for their livelihood and follow 
it throughout the year, but others seek mussels only when their regular wmrk is sus- 
])ended. Thus, in winter especially, the ranks of the regular mussel fishermen are 
considerably augmented by sawmill hands, farm hands, and others. Owdng to the 
increase in the mussel fishery during the past two or three years, it is said that many 
farmers have had difliculty in obtaining men to ivork on their farms. 
It is reported that in lSfi7 there were, between Burlington and Clinton, in 
Iowa, over 300 persons Avho engaged in taking mussels to sell to the button manufac- 
turers at the various towns along that part of the Mississippi. In 1898 the number 
