Assessing the effects of sub‐tropical winter thermal conditions on coolwater fish reproduction

Abstract

AbstractFish populations on equatorward range edges are often the first to exceed thermal bounds in response to climate‐induced warming, increasing risk for local extirpation. For many fishes, regionally specific thermal bounds for reproduction and early life stages are unknown as is the potential for transgenerational acclimation, limiting our ability to identify populations at the greatest risk from warming. Yellow Perch (Perca flavescens, Mitchill 1814), a coolwater species, have a patchy distribution at the southern edge of their North American range, occurring primarily in systems with summertime coolwater refugia. Minimum winter temperatures in these systems are much warmer than in northern locations where long, cold winters result in higher quality eggs compared with short, warm winters. We conducted controlled laboratory experiments with Yellow Perch from the Savannah River, SC to determine how sub‐tropical minimum winter temperatures and durations affected reproduction. We measured spawning success, fecundity, egg and larval quality, and assessed the potential for transgenerational acclimation. We found that minimum winter temperature influenced timing of spawning, but had no effect on spawning success, fecundity, egg size or transgenerational acclimation. Larval size was positively associated with colder winters, but eggs from colder winters also had lower caloric density, suggesting a possible trade‐off between larval size and egg energetic density. Our results provide an improved understanding of the thermal requirements for successful Yellow Perch reproduction at southern latitudes and suggest knowledge of local adaptations is required to accurately predict the impacts of warming on coolwater fishes.