AUTHORS: Benjamin J. Schall, South Dakota Department of Game, Fish and Parks; David O. Lucchesi, South Dakota Department of Game, Fish and Parks; Keith E. Schwartz, South Dakota Department of Game, Fish and Parks; Alison A. Coulter, South Dakota State University; Steven R. Chipps, USGS Cooperative Fish and Wildlife Unit, South Dakota State University
ABSTRACT: Changes to aquatic habitats owing to climate change can impact fish populations. Warming temperatures combined with changes in the magnitude and frequency of precipitation events have resulted in more frequent flooding and increased river flows in portions of the upper Great Plains. The impact of changing flow and increased water temperature on fishes in these systems is not well understood. Therefore, this study was designed to evaluate the impacts of changing water levels and temperature on Channel Catfish and Flathead Catfish growth and condition. Channel Catfish were collected in eastern South Dakota from the James River from 2017-2024 and the Big Sioux River from 2021-2024. Flathead Catfish were collected from the James River in 2018 and 2022-2024. Growth increments were measured from the three most recent pectoral spine annuli, and lengths-at-age were back-calculated. A series of Bayesian generalized linear mixed-effects models were developed to evaluate the relationship between back-calculated lengths and environmental variables, including discharge and cumulative growing degree days (GDD). Fish condition was also assessed by developing annual length-weight regressions and modelling fish weights under varying river discharge and GDD values on the James River. Overall increases in annual growth increment and length-weight regression slopes were observed for Channel Catfish in the James River as river discharge increased. However, growth of Channel Catfish in the Big Sioux River was negatively related to GDD. James River Flathead Catfish condition remained similar across the study years, but growth increments increased with discharge. By modeling potential future environmental conditions under varying climate scenarios, it may be possible to identify how these populations will be impacted by changing climatic conditions and how that may impact their management.
