Chikaskia River _Ictalurus natalis_ _Percina phoxocephala_ _Labidesthes sicculus_ _Lepomis megalotis breviceps_ _Micropterus punctulatus_ _Moxostoma aureolum pisolabrum_ _Moxostoma erythrurum_ _Notropis camurus_ _Pimephales notatus_ _Pimephales tenellus_ _Noturus nocturnus_
The westernmost records for seven species are in the area studied.
4. _Minytrema melanops._ One specimen taken at station G-10 near the mouth of Crab Creek constitutes the present westernmost record. A specimen has been taken by Cross (C-24-51) in the headwaters of the Walnut River.
5. _Notropis boops._ The westernmost record is station G-5 on Grouse Creek. This fish has been reported slightly west of this in Oklahoma on Big Beaver Creek in Kay County (number 4776, Oklahoma A & M College Museum of Zoology).
6. _Notropis volucellus._ Two specimens were taken at station G-8 on Silver Creek.
7. _Percina copelandi._ The westernmost record is from station G-1, two miles above the mouth of Grouse Creek.
The easternmost occurrences of four species are in the area studied. These species are _Hybopsis aestivalis tetranemus_ (Station A-2), _Notropis blennius_ (Station A-1), _Notropis girardi_ (Station A-2), and _Fundulus kansae_ (Station A-2 and Walnut River). These fish are associated with the Arkansas River proper and its sandy western tributaries. In Oklahoma, these fish are found in the Arkansas River as it proceeds eastward and in the downstream portions of some of its tributaries. These fish show little tendency to ascend the streams of the Flint Hills.
The fish fauna of the area studied is transitional between the Ozarkian and Great Plains faunas.
Fluctuation in water level seemed especially important in determining distribution of fishes in the area studied. Variable climate characteristic of the region studied causes recurrent floods and intermittency in streams. Both of these conditions have probably been accentuated by man's modifications of the habitat. The effects of intermittency were most strikingly demonstrated in small creeks of the uplands. The number of species of fish in the highly intermittent streams was small--especially in the uppermost pools sampled--but the actual number of fish was often high even though the number of species was low. In several instances the only fishes found in these isolated pools were _Lepomis cyanellus_ and _Ictalurus melas_. This phenomenon of concentrated numbers of individuals of a few species would indicate the presence of limiting factors that allow only those species most tolerant of the particular factor to flourish.