METHODS
Electrical Fishing Gear
The principal collecting-device used was a portable (600-watt, 110-volt, A. C.) electric shocker carried in a 12-foot aluminum boat. Two 2 × 2-inch wooden booms, each ten feet long, were attached to the front of the boat in a "V" position so they normally were two feet above the surface of the water. A nylon rope attached to the tips of the booms held them ten feet apart. Electrodes, six feet long, were suspended from the tip and center of each boom, and two electrodes were suspended from the nylon rope. The electrodes extended approximately four feet into the water. Of various materials used for electrodes, the most satisfactory was a neoprene-core, shielded hydraulic hose in sections two feet long. These lengths could be screwed together, permitting adjustment of the length of the electrodes with minimum effort. At night, a sealed-beam automobile headlight was plugged into a six-volt D. C. outlet in the generating unit and a Coleman lantern was mounted on each gunwale to illuminate the area around the bow and along the sides of the boat (Pl. 3a). In late summer, 1959, a 230-volt, 1500-watt generating unit, composed of a 115-volt, 1500-watt Homelite generator was used. It was attached to a step-up transformer that converted the current to 230 volts. The same booms described above were used with the 230-volt unit, with single electrodes at the tip of each boom.
A 5.5-horsepower motor propelled the boat, and the stunned fish were collected by means of scap nets. Fishes seen and identified but not captured also were recorded. On several occasions fishes were collected by placing a 25-foot seine in the current and shocking toward the seine from upstream.
The shocker was used in daylight at all six stations in the three years, 1957-'59. Collections were made at night in 1958 and 1959 at the middle Neosho station and in 1959 at the lower Neosho station.
Seines
Seines of various lengths (4, 6, 12, 15, 25 and 60 feet), with mesh-sizes varying from bobbinet to one-half inch, were used. The 4-, 12-, and 25-foot seines were used in the estimation of relative abundance by taking ten hauls with each seine, recording all species captured in each haul, and making a total count of all fish captured in two of the ten hauls. The two hauls to be counted were chosen prior to each collection from a table of random numbers. Additional selective seining was done to ascertain the habitats occupied by different species.
Trap, Hoop, and Fyke Nets.—Limited use was made of unbaited trapping devices: wire traps 2.5 feet in diameter, six feet long, covered with one-inch-mesh chicken wire; hoop nets 1.5 feet to three feet in diameter at the first hoop with a pot-mesh of one inch; and a fyke net three feet in diameter at the first hoop, pot-mesh of one inch with wings three feet in length. All of these were set parallel to the current with the mouths downstream. The use of trapping devices was abated because data obtained were not sufficient to justify the effort expended.
Gill Nets
Gill-netting was done mostly in 1959 at the lower Neosho station. Use of gill nets was limited because frequent slight rises in the river caused nets to collect excessive debris, with damage to the nets.