ARTICLE Optimum Electrofishing Waveforms and Parameters to Induce Immobilization of Juvenile Grass Carp Andrew S. Briggs* Michigan Department of Natural Resources, Lake St. Clair Fisheries Research Station, 33135 South River Road, Harrison Township, Michigan 48045, USA Jan C. Dean Dean Electrofishing, LLC, 14061 Arranwood Lane, Fishers, Indiana 46038, USA James C. Boase U.S. Fish and Wildlife Service, Alpena Fish and Wildlife Conservation Office, 480 West Fletcher, Alpena, Michigan 49707, USA Patrick M. Kocovsky U.S. Geological Survey, Great Lakes Science Center, Lake Erie Biological Station, 6100 Columbus Avenue, Sandusky, Ohio 44870, USA James A. Luoma U.S. Geological Survey, Upper Midwest Environmental Sciences Center, 2630 Fanta Reed Road, La Crosse, Wisconsin 54603, USA Abstract 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 fre- quencies 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, respec- tively, may be more effective. Water temperature was positively related to voltage gradient immobilization thresh- olds 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. *Corresponding author: briggsa4@michigan.gov Received October 16, 2018; accepted April 29, 2019 North American Journal of Fisheries Management © 2019 American Fisheries Society ISSN: 0275-5947 print / 1548-8675 online DOI: 10.1002/nafm.10303 1