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Tuesday, February 7 • 2:00pm - 2:20pm
Technical Session. The Effects of Electrofishing Waveform on Immobilization Thresholds for Blue Catfish

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AUTHORS: William Morris, Missouri Cooperative Fish & Wildlife Research Unit; University of Missouri;
Craig Paukert, U.S. Geological Survey, Missouri Cooperative Fish & Wildlife Research Unit; University of Missouri; Zach Ford, Missouri Department of Conservation; Andy Turner, Missouri Department of Conservation; Jan Dean, Dean Electrofishing, LLC

ABSTRACT: Electrofishing is a common sampling technique used to collect catfish. However, there is a need to standardize electrofishing protocols to better assess the status and trends of catfish populations. Applying the power transfer theory, our objective was to determine if the immobilization threshold (i.e., minimum voltage needed to immobilize fish) for Blue Catfish differed by electrofishing waveform, with the goal of determining the most efficient settings to collect Blue Catfish. We compared immobilization thresholds between 40 pulsed DC waveforms for 200 Blue Catfish ranging from 35 to 50 cm. Waveforms ranged from eight to 300 pulses per second (hz), with duty cycles ranging from 10 to 40% at each pulse frequency. Each Blue Catfish was placed in a controlled tank with steel electrodes on each end attached to a backpack electrofisher and voltage was increased from one volt until immobilization was observed. The voltage at which twitch, immobilization, and surface responses were observed were independently recorded for each trial by four observers. High frequency waveforms (80-300 hz) had the lowest immobilization thresholds, but only 24% of the fish showed a surface response under the five waveforms with the lowest average immobilization threshold. Four low frequency (8-12 hz) waveforms, which are more commonly used for Blue Catfish collection, produced a surface response in >80% of fish, but immobilization thresholds for these waveforms varied from the 10th lowest (12 hz) to the highest (8 hz) of all waveforms tested. Our results suggest that Blue Catfish may be best immobilized by high frequency waveforms, but the lack of a surfacing response under these waveforms may make them less efficient at capturing fish in a natural setting. A better capture prone response (i.e. surfacing) is produced under lower frequency waveforms where more of a threshold buffer exists between twitch and immobilization.

Tuesday February 7, 2017 2:00pm - 2:20pm CST
Grand Ballroom B