COMMON FISHES OF MISSISSIPPI RIVER 
215 
mouths, rasping off the flesh and sucking the blood of their helpless victims, which 
swim about unable to dislodge them. The ring muscle of the mouth works all the 
teeth at once against the selected surface, and both scales and skin aie soon boied 
through. The relentless voracity of these fearful pests of our fresh waters is shown 
by the deep holes which they make in the living bodies of their victims and by their 
own intestines gorged with blood and flesh. Their hold is probably seldom loosened 
by any fish, unless by accident.” (Forbes and Richardson, 1908.) 
The paddlefish, when more abundant, were conspicuously the favored hosts of 
lampreys, which are said to be common on all large fishes except the game fishes. 
They are now seen most frequently on catfish, sturgeon, carp, and buffalo fish. 
They are taken most plentifully in spring and fall and are said to found on fish 
caught from beneath the ice. While there are reports that lampreys are seen less 
commonly in Lake Pepin in recent years, they are plentiful enough in the region from 
Fairport to Keokuk. 
FRESH-WATER MUSSELS 
The report would not be complete without reference to the fresh-water mussels, 
which are the basis of a very important industry of button manufacture. The 
mussels as adults are sedentary in habit, and they can be affected directly by the 
power development only in the region covered by the impounded water; but the 
larval mussels are, in a sense, migratory, for they are parasitic on fish, which move 
from place to place, unwittingly conveying the young mussels and distributing 
them more or less widely as they fall from the gills or other parts of the fish after 
completing the metamorphosis from larval to adult form of body. The mussels, 
then, are affected as the fish are affected. The relations of the several species of 
mussels to the several species of fish have been fully treated in another report (Coker, 
Shira, Clark, and Howard, 1921), and some specific cases pertinent to this study 
have been mentioned in earlier pages of this report. Since most of the possible 
effects of the dam upon mussels are conditioned upon the effects upon fishes, it 
would be a redundancy to discuss the effects of the second order in detail. We 
will, however, refer to a few significant facts that have not been brought out pre- 
viously. 
The old rapids above Keokuk was a famous place for niggerhead mussels of the 
finest quality. The change from rapids to bed of lake at once rendered bottom 
conditions in that region unfavorable to that particular mussel; the ensuing sedi- 
mentation probably destroyed what mussels were there and prevented their replace- 
ment by others of different habit. F. C. Vetter, of Muscatine, told the author in 
1926 that he had recently had a diver go down over the old rapids to see if the nigger- 
head mussels still remained. The bottom was found deeply covered with fine silt, 
into which the diver sank so far that Mr. Vetter was afraid to permit him to continue 
the search. The mussel fauna of former times is gone from that region. 
There is the possibility that in other parts of the lake there may be bottoms 
suitable for other kinds of mussels, such as the Lake Pepin mucket, which thrives 
so well and proves so valuable in Lake Pepin and Lake St. Croix. For several years 
the Fairport station had made attempts to introduce the Lake Pepin mucket in 
Lake Keokuk. Some mussels from a plant made near Fort Madison by Superin- 
tendent Hessen were seen in 1926, having been recently recovered from the lake. 
It is very desirable that these attempts be continued, but it is by no means to be 
assumed that the conditions of bottom in Lake Keokuk will permit of a population 
