Electrofishing for crappies: electrical settings influence immobilization efficiency, injury, and mortality

Chad R Dolan, L E Miranda, Theodore B Henry

    Research output: Contribution to journalArticle

    Abstract

    Continuous direct current (DC) and pulsed DC (PDC) of varying frequency and pulse period are commonly used to immobilize and collect crappies Pomoxis spp. in freshwater. However, little information is available about the minimum electrical-setting thresholds required for immobilization or how the settings relate to incidence of injury. We investigated the effect of increasing power densities on the immobilization and injury of black crappies P. nigromaculatus (average total length = 154 mm) treated with DC and various PDC settings. Forced swimming toward the electrodes was observed in black crappies exposed to DC, but that was less apparent for PDC. The minimum peak power densities required to immobilize black crappies ranged from 0.10 to 6.5 MW/cm(3) and depended on pulse frequency and period. The incidence of hemorrhaging ranged from 0% to 50% and that of spinal damage from 9% to 45%. However, the severity of injury also depended on pulse frequency and period. No fish suffered mortality at or below the immobilization thresholds, but mortality ranged from 0% to 15% at settings above the thresholds. Mortality was observed with PDC settings of 15 Hz only. Fish that were tetanized following electrical treatment were more prone to injury than those that exhibited narcosis.

    Original languageEnglish
    Pages (from-to)1442-1451
    Number of pages10
    JournalNorth American Journal of Fisheries Management
    Volume22
    Issue number4
    DOIs
    Publication statusPublished - 2002

    Keywords

    • TROUT
    • ELECTROSHOCK

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