Soon after rains restored flow in these intermittent creeks _L. cyanellus_ and _I. melas_ appeared in parts of the channels that had previously been several miles from the nearest water. Rapid upstream movements of other species after rains was also noted.
It was impossible to ascertain the precise effects of gradient and bottom-type on distribution, but certain species such as _Notropis blennius_, _Notropis girardi_, and _Fundulus kansae_ were taken only in streams with sandy bottoms. _Notropis deliciosus_ and _Hybognathus placita_ were most abundant over sandy bottoms.
The high gradient of upland tributaries in the Flint Hills area produced turbulence and bottoms predominantly of rubble. A fauna of which _Etheostoma spectabile_ and _Campostoma anomalum_ were characteristic existed in these waters while they were flowing. As flow decreased and intermittency commenced, qualitative and quantitative changes in the fish faunas were observed. Gradient did not change during drought, but turbulence did. Because turbulence varies with water level as well as gradient, the effect of gradient on fish distribution ultimately is linked to climate.
Probably the small number of fish taken on the Walnut River in comparison with other eastern Kansas rivers (Verdigris, Neosho) results, in part, from the long-term pollution of the stream noted by Clapp (1920:33) and Doze (1924). No percid fishes, black bass, or madtom catfish were taken on the Walnut in Cowley County and the species of _Notropis_ numbered only three.
Four faunal associations seem to be recognizable in the area.
This fauna contained _Notropis girardi_, _Notropis blennius_, _Hybopsis aestivalis tetranemus_, and _Fundulus kansae_ which, in this area, did not seem to wander far from the sandy main stream of the Arkansas. Minnows abounded; _Notropis lutrensis_ and _N. deliciosus missuriensis_ predominated; and _Notropis girardi_, _N. percobromus_, and _Hybognathus placita_ were common. In quiet backwaters, coves, and shallow pools _Gambusia affinis_ occurred in great numbers. _Lepisosteus osseus_ seemed to be the most important predator.
The Walnut River in Cowley County supported large populations of deep-bodied suckers, carp, and gar. _Notropis lutrensis_ and _N. percobromus_ were characteristic minnows. _Lepomis_ _humilis_ abounded at some stations. The fauna of the main stream of the Walnut River was somewhat intermediate between that of the Arkansas River and that of the three streams considered below. Fifteen of the species common to the Big Caney, Elk, and Grouse systems were also taken in the Walnut River main stream. Thirteen species were common to the Walnut and Arkansas rivers. Seven species were common to all these streams.