The relative abundance of each species in the upper Neosho was calculated from cumulative results obtained by use of the shocker in seven areas in 1959. Population estimates were made by collecting fish with the shocker, marking them by clipping fins or staining them in Bismark Brown Y at a concentration of 1:20,000 (Deacon, 1961), returning them to the stream, and making a second collection three hours (Areas 1 and 3) or 24 hours (Area 6) later. The same area was shocked again within two to eight days. Collections throughout the one-half-mile section yielded information on movement. Changes in the Fauna at the Upper Neosho Station, 1957 Through 1959. The following discussion is based principally on collections made with rotenone in 1957, 1958 and 1959 (Table 12). Other supplementary data aid in understanding the changes that occurred after the resumption of normal flow at the upper Neosho station. The population in 1957 was strongly dominated by black bullhead and young-of-the-year channel catfish. Other common species were long-eared sunfish, red shiner, yellow bullhead, orange-spotted sunfish and green sunfish. This fauna, with the exception of young-of-the-year individuals, was a fauna produced during the years of drought. Deacon and Metcalf (1961:318-321) found a similar fauna in streams of the Wakarusa River Basin that had been seriously affected by drought. The black bullheads taken in 1957 were predominately yearlings. It is likely that by 1956 the total fish population in the upper Neosho had been decimated by drought. The ponded conditions prevalent in that year were conducive to production and survival of young black bullheads. Fig. 3 shows that this dominant 1956 year-class reached an average length of approximately 6.5 inches by August, 1959. Reproduction by black bullheads was limited in 1957, 1958, and 1959, and slight reduction in relative abundance occurred from 1957 to 1958. The relative abundance in 1959 remained nearly stable. If stream-flow remains essentially continuous for the next few years, the number of black bullheads probably will decline as individuals of the 1956 year-class reach the end of their life-span. Reference has been made to the large hatch of channel catfish in 1957, in a discussion of that species. Conditions for survival of young channel catfish at the upper Neosho station in 1957 were good because there was continuous flow over many gravel-rubble riffles, which were largely unoccupied by other fish, in the spring and summer of 1957. TABLE 12. PERCENTAGE-COMPOSITION OF THE FISH-FAUNA AT THE UPPER NEOSHO STATION IN 1957, 1958 AND 1959, AS COMPUTED FROM COLLECTIONS OBTAINED BY USING ROTENONE.