Factors affecting walleye and sauger recruitment in Lewis and Clark Lake, South Dakota, 2001–2022

Abundance of adult walleye (Sander vitreus) and sauger (Sander canadensis), two important sport fishes, decreased significantly during 2001–2022 in Lewis and Clark Lake, a border water between Nebraska and South Dakota, despite walleye fingerling stocking and stable age-0 abundance of both species. We sought to identify factors that drove variation in age-0 abundance from 2001 to 2022 using an information theoretic approach. Age-0 walleye catch per unit effort (CPUE) was correlated to mean monthly outflow, mean annual precipitation, and mean April gauge height in a delta. Age-0 sauger CPUE was correlated to adult conspecific CPUE, mean April Heating Degree Days, and mean annual precipitation. Our findings suggest that both biotic and abiotic factors were important for explaining variation in age-0 CPUE of sauger, but mainly abiotic factors for walleye. As such, manipulation of abiotic factors (i.e., outflow) by installing entrainment barriers may be more effective than manipulation of biotic factors (i.e., stocking).