Optimum electrofishing waveforms and parameters to induce immobilization of juvenile Grass Carp.
Grass Carp Ctenopharyngodon idella, a nonnative species to North America, are known to cause negative impacts to aquatic habitats and aquatic communities. Numerous fisheries techniques have been used in an attempt to control or eradicate Grass Carp, including electrofishing. However, electrofishing efficiency for Grass Carp has been variable, and optimum electrofishing waveforms and parameters for inducing a capture-prone response have not been determined. The objective of this study was to determine the optimum electrofishing waveforms and parameters to induce a capture-prone response at various water temperatures and conductivities in juvenile Grass Carp in a controlled, laboratory setting. Results indicated that rectangular pulse waveforms with 60-100 Hz frequencies were most effective for immobilization of juvenile Grass Carp. While all duty cycles tested (20-48%) at these frequencies were effective we found that at 60 Hz and 80 Hz frequencies, 24% and 30% duty cycles, respectively, may be more effective. Water temperature was positively related to voltage gradient immobilization thresholds whereas ambient water conductivity and fish size were inversely related to voltage gradient immobilization thresholds. This study provides important information to those seeking to control, eradicate, or detect Grass Carp using electrofishing and provides a framework for future studies focusing on adult Grass Carp.