AUTHORS: Robert Mapes, University of Toledo; Christine Mayer, University of Toledo; Song Qian, University of Toledo; Robert Hunter, US Geological Survey; Matt Acre, US Geological Survey; James Roberts, US Geological Survey; Ryan Young, US Fish and Wildlife Service; Ryan Brown, Michigan Department of Natural Resources; Lucas Nathan, Michigan Department of Natural Resources; Eric Weimer, Ohio Department of Natural Resources; John Dettmers, Great Lakes Fishery Commission
ABSTRACT: Grass carp (Ctenopharyngodon idella) control efforts in the Great Lakes follow an adaptive management framework to continually improve removal efficiency. Initial planned action events suggested a combination of electrofishing toward trammel nets (combination method) was the most effective method to herd fish for capture. However, these initial attempts had low catches and were focused on locations with low apparent grass carp densities. Following substantial project expansion and increased effort in areas with higher apparent densities of grass carp, field crews began to experiment with other methods. A second post-hoc method comparison found electrofishing without the trammel nets to be at least >2.8 times more efficient than the combination method. The project adapted and began focusing on electrofishing while continuing to explore ways to improve efficiency by leveraging telemetry information and experimenting with other capture methods. Field crews tested passive overnight gill net sets in locations informed by telemetry and previously high capture rates. These efforts collected more grass carp in one night than the previous month of electrofishing. Expanding gill net use has contributed to more grass carp being captured during 2024 than in any other year since control efforts began in 2018. Designing a project to capture novel species with limited information is challenging and therefore an adaptive approach that analyzes data in real time is vital to invasive species control. A multi-disciplinary team with diverse skills, enables near real time incorporation of information to inform ongoing removal efforts. Although adapting to new gears has resulted in increased captures, changing methods creates challenges evaluating the effectiveness of the program through statistical models. The adaptive management framework allows for Great Lakes Grass Carp practitioners to quickly leverage data as it is collected and make concurrent changes in the field, which is invaluable to control the spread of invasive carp.
