Rotenone was applied to an intermittent pool in 1957. In 1958 and 1959 rotenone was applied to the upper end of a pool and mixed by agitating the water. The concentration in the pool was maintained by slowly introducing part of the rotenone into the riffle at the head of the pool. This was the most effective means of obtaining a large sample of fish from the deeper, slowly flowing water of the upper Neosho. Pools in which rotenone was used had areas of as much as one-half acre and depths in excess of six feet.
Shocker
In 1959 the shocker was used extensively in several areas of the upper Neosho. Because of the small size of the stream, "tennis-racket" electrodes were used effectively by two men—one carrying the electrodes and one picking up fish and placing them in a live-box. In fast water, many fish floated into a seine placed across the lower end of the area. A large segment of the population was collected in this manner. Areas in which fish were collected by means of the shocker included riffles, and pools having flowing water no more than three feet in maximum depth. The bottom-type was usually gravel, rubble or bedrock, but a small amount of mud bottom was present in many pools.
Because of the necessity of wading, we could not use the shocker effectively in water more than three feet deep. In addition, turbidity of the water prevented effective collection of stunned fish in the deeper pools. Therefore, rotenone was more effective in deep water than was the shocker. In shallow, swift riffles and pools, the shocker yielded more reliable samples than did rotenone, because of difficulty in maintaining adequate concentrations of rotenone where flow was swift.
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.