KEOKUK DAM 
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suggests the increase of its general productiveness, but the plankton development in 
that lake has not been found comparable to the development in Lake Pepin. Lake 
Keokuk is subject to more of the vicissitudes of ordinary sections of the river. 
The statistical surveys of fisheries in Lake Pepin for 1922, when compared with 
surveys of 1914 and 1917, indicate an increasing catch of paddlefish, but oral reports 
in 1926 and the survey of 1927 indicate a recent scarcity of this and other commercial 
fishes. The surveys made for Lake Keokuk show increasing yields in 1922, with a 
corresponding drop in 1927, and this is in accord with the reports of commercial 
fishermen. The evidence indicates that the species finds in Lake Keokuk favorable 
conditions for reproduction and growth. The effect of the power development, if 
any, on the paddlefish fishery of the upper river is favorable. However, somewhere 
in connection with the dam a noticeable number of paddlefish receive serious injuries, 
the cause of which we have been unable to ascertain. 
The decline of the rock sturgeon in the upper river can not be associated with the 
the presence of the dam, as that fish had been virtually lost to the upper part of the 
river before the dam was built. The shovelnose sturgeon, small but very valuable, 
may be declining in importance in the river above the dam, but the evidence is not 
very clear. Further inquiries should be made during a season of good flow of water, 
such as had not prevailed for several years before 1926. The lake offers no advantages 
for it. Since the fish seems to be holding its own better below the dam, it is possible 
that breeding conditions are better there and that the fish would be more abundant 
in the upper river were the dam not an obstruction to its upward range. Some 
breeding evidently occurs above the dam. 
Gar pikes are undiminished in numbers, if not increasing, but that condition can 
not well be associated with the dam. The yellow sandshell, the most valuable of all 
mussels, which propagate with the aid of gar pikes, is greatly increasing in abundance in 
the upper river, a condition very desirable in itself but probably due to the increasing 
numbers of wing dams built in aid of navigation and serving as protection to areas of 
relatively still and shallow waters along the shores, where the sandshells may thrive. 
The bowfin (or dogfish), formerly despised generally, is now in some demand, but 
is not found in the upper Mississippi in such abundance as would be expected. Its 
extremely predacious habit makes it an undesirable element. 
The mooneyes appear to have been unaffected by the dam. The gizzard shad, 
very valuable as food for other fishes, might be expected to multiply abundantly 
in the lake, but we have no evidence yet of its notable increase. 
The river herring, while still abundant below the dam, does not now appear in 
the upper river in anything like the numbers observable in former times. Undoubt- 
edly it breeds above the dam as well as below, but we are led to the conclusion that 
the upper river formerly was stocked largely by migration from more southern waters, 
and that the effect of some comparatively recent change has been to cause a great 
reduction in the abundance of river herring in the upper river. That the darn was 
the effective factor in this change is strongly evidenced by the fact that diminution 
in numbers of river herring was observable immediately after the dam was built 
and was most pronounced at that time. Apparently there has been a partial recovery, 
but river herring are found now in far less abundance than formerly. The valuable 
niggerhead mussel, dependent in nature upon the river herring for its early develop- 
ment, is gradually declining in importance in the upper Mississippi. We can not, 
of course, say to what extent the decline is due to the intensive fishery for a mussel of 
