Behavioral responses of Murray cod Maccullochella peelii peelii to pulse frequency and pulse width from electric fishing machines

The effective electrical conductivity (C_f) of Murray cod Maccullochella peelii peelii was evaluated as part of an investigation into effective electric fishing settings for this important species. We describe an evaluation of minimum thresholds of power applied to an electrical field required to elicit four responses (escape, forced swimming, immobilization, and narcosis) from Murray cod. Estimates of C, varied from 46 to 80 μS/cm depending on the response threshold of interest; these results support hypotheses that a global standard for C_f could be applied to power transfer calculations. Results indicate that at 60 Hz, pulse widths (PWs) of 6.7-10 ms are most efficient; however, the electrical dose required for all responses is minimized using higher frequencies resulting in PWs of less than 2 ms. Our observations support other work suggesting that the complexity and range of responses are determined jointly by the nature of the stimulus and the orientation to the field. We suggest that a measure of electrical dose required for a given stimulus provides insight into settings for maximizing electric fishing effectiveness.