American Fisheries Society 181 



guished from it successively with the retreat of the over- 

 flow, but connected with it and contributing to it at its 

 lowest levels, and the river itself has, as a home for fishes, 

 so many of the characteristics of a lake, that its problems, 

 although complex and difficult, do not compare unfavorably 

 in importance with those of any lake in the world of equal 

 area. Its average fall through the lower four-fifths of its 

 course is only 1 2/3 inches per mile, and there are stretches 

 of several miles throughout which its fall per mile is only 

 about a quarter of an inch. Its current at low water, as 

 it swings from side to side of its broad and level flood- 

 plain, is as slow, at the dams, as half a mile per hour, and 

 although the midstream flow at high water is, of course, 

 much stronger, there are even then extensive backwater 

 shallows in which a fish could hardly tell whether it was 

 swimming upstream or down. 



It is one of the most interesting features of our field of 

 operation that we are able to bring easily into comparison 

 the system of life in this sluggish, lake-like stream with 

 that of the swift Mississippi, into which it flows, or that of 

 the still swifter Missouri, whose mouth is only twenty-four 

 miles from its own. Even the Ohio, very different phy- 

 sically and biologically from either of the other three, is not 

 beyond our reach, and comparative studies of all these 

 streams have been begun by us this year. 



In such an investigation as is here proposed, the founda- 

 tion inquiry which must fix our beginning points and show 

 where the principal emphasis should at first be placed, is 

 this: Just what is it that we need to know in order that 

 we may be in a position to do all that we ought to under- 

 take, for the conservation and increase of our aquatic 

 resources? To this inquiry I must make, at first, a general 

 and perhaps a disappointing answer. It is perfectly evident 

 that if we wish to maintain or to improve the conditions 

 of life for the fishes of our rivers, we must first know what 

 the present conditions are, and which of these are the most 

 important to our purpose. We might, it is true, hatch 



