Climate Change and Piscivory within Age-0 Largemouth Bass Cohorts in Wisconsin Lakes

Largemouth bass abundance has increased in many northern Wisconsin lakes over the last decade, due in part to favorable climatic conditions. Increased bass abundance has important implications for food web dynamics and fisheries management. Specifically, largemouth bass can switch to piscivory during their first year of life, but age-0 bass in many Wisconsin lakes rarely attain lengths associated with piscivory in previous studies. Climatic changes that result in earlier hatching of largemouth bass in Wisconsin lakes could lead to increased piscivory, which could affect food web dynamics. Our objective was to determine if temperature-based changes in hatch timing could increase the prevalence of piscivory in age-0 largemouth bass cohorts in Wisconsin lakes. Our initial sampling suggests that piscivory in age-0 largemouth bass cohorts was rare in the 8 lakes we sampled (only 3% of all bass examined) and was restricted to relatively large individuals (≥ 70 mm total length). Changes in hatch timing alone would have to be substantial (i.e., hatching occurring > 10 d earlier) to measurably increase the percentage of bass attaining 70 mm TL, but hatch timing coupled with enhanced growth could result in measurable increases in the number of bass attaining lengths associated with piscivory.