AUTHORS: Dillon Weik, University of Toledo; Christine Mayer, University of Toledo; Tammy Wilson, US Geological Survey; Ryan Young, US Fish & Wildlife; Eric Weimer, Ohio Department of Natural Resources; John Dettmers, Great Lake Fishery Commission
ABSTRACT: Invasive grass carp have been captured in Lake Erie since the mid-1980s, and spawning in tributaries to the lake was confirmed in 2015. In response, a multi-jurisdictional partnership was established to target grass carp for removal with increasing effort since 2017. However, capture data is limited, making supplemental biological data, such as growth histories estimated from bony structures, especially useful in describing trends in the population or individual traits. Age was estimated using vertebrae for all fish removed from Lake Erie since 2012, and growth was back-calculated using the Biological Intercept Model. The back-calculated growth was then fitted to a Von Bertalanffy Growth Function. Lake Erie grass carp age-at-maturity (as indexed by a decrease in growth rate) of diploid fish was estimated to be ~3 years. In contrast, literature derived age-at-maturity ranges from 1-10 years. Current removal methods select fish > 880 mm (age-4). Consequently, recruitment may occur before fish are vulnerable to removal. Therefore, future efforts are needed to target smaller fish by exploring alternative habitats or examining new sampling gears to remove these cryptic individuals before they are able to successfully recruit to the population.
