What Drives Temporal and Spatial Variation in Early Survival and Growth of Largemouth Bass?

Growth patterns in first-year largemouth bass can vary substantially within and between populations. The goal of this study is to understand what drives variation in body size within a cohort at any time during the first season of growth and what drives differences in body sizes across populations.  We combined information about hatch dates (from analysis of otoliths), diets (from analysis of stable isotopes), prey availability, reservoir water temperatures, and reservoir hydrology to explain growth rate variation across hatch dates within a population and across two Ohio reservoirs. Within reservoirs, we observed hatch-date-dependent growth rates, which apparently were driven by food availability and temperature. The substantial growth rate differences we observed between reservoirs were driven by food availability. General productivity of the reservoirs and, thus, food availability in the reservoir, was largely driven by watershed-level mechanisms. First-year largemouth bass from reservoirs in agricultural landscapes, with high levels of nutrient inputs, grew much more rapidly than first-year largemouth bass from reservoirs in forested landscapes. Given our results, we expect within-reservoir growth patterns may vary across years, but that landscape-driven differences between reservoirs will remain consistent over time.