298 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
THE FISHING-GROUNDS. 
The Iowa ami Illinois button factories located on the Mississippi River obtain 
their supply of shells from grounds which extend from Fort Madison, Iowa, to Sabula, 
Iowa. This section of the river is 167 miles in length, following its sinuosities, although 
the distance in an air line between the points named is only 118 miles. The average 
breadth of the river is two-lifths of a mile, the maximum unobstructed width being 
about 1 mile. Just north of Campbell Island, between Leclaire and Davenport. 
This part of the Mississippi is quite shallow at the mean stage of the water. 
The usual depth in the channel is 12 to 14 feet, the deepest water being only 33 feet. 
On either side of the channel the bottom generally slopes gradually to the shores. 
In the latter part of summer and the early tall the depth is always reduced by the 
diminution in the volume of water coming downstream, while in winter, spring, and 
early summer the river is swollen by rains and melting snows; there being every 
season a freshet of greater or less severity. 
The character of the bottom varies greatly, but it is usually sandy, sand-bars and 
low sandy islands being common features. There are, however, more or less extensive 
areas of muddy bottom, and in some places rocky or gravelly bottom xirevails. 
Owing to the shoalness of the river and the character of its bed, the annual 
freshets produce marked changes in the bottom topography. These changes have an 
imiiortant relation to the mussel beds, which are sometimes entirely swept away and 
sometimes comidetely destroyed by being covered with sand or mud; such beds of 
dead shells are not infrequently found by the tishermen when subsequent freshets 
have swept off the overlying sand or mud. 
Throughout the river section mentioned, mussels are found in scattered or in 
condensed bodies. The natural tendency of some of the species is to form more or 
less dense beds, while others seem to be uniformly distributed. Considered as a whole, 
this part of the Mississippi River is undoubtedly one of the most favored sections 
of the United States as regards abundance and variety of mussels adapted for buttons. 
By far the greater iiortion is taken from special areas on which they are more 
abundant and more closely grouped than in other places. Such beds, which are 
sometimes of great extent, have their iirincipal axis lengthwise the river, and are often 
quite narrow. 
On some grounds practically all of the mussels are of one species, while on others 
several species may be mixed in varying quantities. The largest and most comiiact 
beds are formed of '‘niggerheads” and “muckets.” On new grounds the ‘Oiigger- 
heads” are sometimes so thickly disposed that xiractically the entire bottom over a 
large area is covered, and the shells are often found several layers deep. In holes 
or depressions in the sandy or muddy bottom “niggerheads” are often discovered in 
thick piles, and many bushels may be taken from one of these holes. 
Owing to the crowding of the mussels, some of the fishermen think that fishing is 
beneficial to the beds, in that it spreads the mussels over a larger area and iiermits a 
more rapid growth and increase of those that remain. There is a popular belief 
among some of the fishermen that dejileted beds may be reestablished in three j^ears — 
that is, the mussels are thought to reach a marketable size in three years after the 
young are hatched. Most of the fishermen and manufacturers, however, have no 
definite knowledge as to the rate of growth, ajthough all think it more rapid than is 
actually the case. 
