136 
BULLETIN OF THE BUREAU OF FISHERIES 
very slow growth or to what extent it is attributable to the reduction in numbers 
of the fish upon which the mussel is dependent. 
The Ohio shad in upstream migration at the season of spawning is stopped by 
the dam. Unfortunately this fish has been so little known that we have no informa- 
tion whatever regarding its occurrence in the river before the dam was built. 
Eels bred in the sea are virtually estopped from passing into the upper river. 
Small eels are reported to occur at times in substantial numbers at the base of the 
dam. The eel may be expected to become quite rare in the Mississippi and trib- 
utaries entering it above Keokuk unless young eels can be planted above the dam. 
Of the catfishes, only the Fulton cat is affected adversely by the dam. It is 
there stopped in northward migration, but it probably never ascended the river far 
above the site of the dam. It seems certain that they were once seasonally abundant 
in the Des Moines Rapids, which are now submerged by the water of the lake. 
There has occurred a notable increase in the local abundance of the channel 
catfish and niggerlip catfish in Lake Keokuk, due undoubtedly to the favorable 
conditions provided by' the lake for breeding and growth of catfishes. 
Excluding the blue sucker, none of the “suckers” seems to have been unfavorably 
affected by the dam except in so far as the lake, with its still waters, has made that 
particular locality unfavorable for such species as are addicted to swiftly flowing water. 
The blue sucker presents a problem. Up to about the time the dam was built 
the blue sucker was very abundant in swift water for a limited season in each year. 
Since that time it has almost disappeared from the river above the dam and, seem- 
ingly, below it as well. As the indications are that the fish was strongly migratory 
in habit, there is the probability that the dam has shut it off from its best breeding 
grounds and that the sucker stock of the river above and below the dam has suffered 
in consequence. We do not know of a type of fishway that could have been used to 
obviate the difficulty. 
There is found no reason to believe that the dam, acting as an obstruction, has 
had any significant effect upon the abundance of the buffalo fishes in any parts of 
the river unless, perhaps, quite locally. It has been said by one experienced fishery 
manager that “southern” buffalo were greatly diminished in Lake Pepin after the 
dam; but to suppose that Lake Pepin is contingent upon the river 500 miles below 
for its stock of any species of buffalo fish involves assumptions regarding the natural 
history of buffalo fishes that are not justified by any body of evidence. 
The favorableness of conditions for reproduction of buffalo fishes and carp in 
Lake Keokuk unfortunately has been reduced by the drainage of large areas of 
overflow lands since the dam was built. 
The dam as a barrier has had no significant effect upon the basses, crappies, 
and sunfishes. The lake offered favorable conditions for the multiplication and 
growth of such fishes, but its advantages have been lessened by the drainage of the 
Green Bay district. 
As regards the pike perches, it is not probable that the dam has any significant 
effect upon the abundance of the fishes unless it be comparatively local. Too little 
is yet known in reference to the migratory habits of the sauger, the only species 
that could be affected seriously by the dam. 
There is no evidence of effects, one way or the other, upon the white bass or the 
yellow bass. 
