Effectiveness of an Electrofishing System for Collecting Flathead Catfish

Three battery-powered pulsed DC electrofishing units were built and used to collect flathead catfish (Pylodictis olivaris) in a 50-km section of the Flint River, Georgia, to study the dramatic population expansion of that species following introduction. Peak collecting efficiency was achieved at 20 Hz frequency and pulse width of 0.4-0.5 ms. Power of 250-350 volts and 3 amps were needed to collect flathead catfish effectively in conductivities of 80-155 umhos/cm. Fishing downstream in a figure-S pattern with a 12-m anode wire hanging from the stern was effective in a variety of depth, substrate, and flow conditions. Efficiency was increased when a chase boat was deployed to net fish due to the large effective electric field. Efficiency was significantly reduced below 20° C. During 35 trips and 78.4 hours of electrofishing, 3,266 flathead catfish were collected. Catch rates increased from 18 fish per hour in May to 85 fish per hour in October and declined in November to 40 fish per hour. Catfish total length ranged from 39 to 1,107 mm and length-frequency analysis suggested that the method was not size selective for fish larger than young-of-theyear (> 150 mm).

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