The influence of embryo incubation temperature on later life aerobic performance of Lake Whitefish (Coregonus clupeaformis) and Yellow Perch (Perca flavescens)

Abstract

Temperature represents one of the most influential abiotic factors affecting all living organisms. Ectotherms, including fish, can be affected by temperature at the cellular, individual, population, and community levels. In modern times, climate change and thermal pollution pose major threats as they threaten to elevate water temperatures, therefore limiting optimal thermal habitats and exposing species to suboptimal environmental conditions. While adult fish of many species have the capacity to avoid these thermally impacted areas, early life stages (i.e., embryonic, larval, and juvenile) are typically limited in mobility and lack the ability to avoid these areas. These early life stages are especially vulnerable, as this is a time of rapid growth and development. While numerous studies have evaluated the effects of temperature during development on hatching success, developmental rates, and phenotypic plasticity, few have assessed its effects on later life whole-animal performance. I used intermittent swim respirometry to evaluate the effects of embryo incubation temperature on two measurements of whole-animal aerobic performance: aerobic scope and critical swimming speed. I chose to use two species of fish that use distinct reproductive characteristics, the fall spawning Lake Whitefish and the spring spawning Yellow Perch. I hypothesized that whole-animal aerobic performance of both species would be reduced when embryos were incubated at temperatures 3 °C above optimal. I also hypothesized that Lake Whitefish would be impacted more drastically than Yellow Perch due to their narrower thermal tolerance. Finally, I predicted that whole-animal aerobic performance would be maximized at temperatures near the thermal preference of the species, respectively. To test my hypotheses, I first incubated Lake Whitefish and Yellow Perch embryos at 2 and 5 °C, and 15 and 18 °C, respectively. I then reared Lake Whitefish at common-garden temperatures of 12 °C for 14 to 16 months and Yellow Perch at 18 °C for and 9 to 12 months. Following the rearing periods, Lake Whitefish and Yellow Perch were split into experimental temperature groups and acclimated to 15 and 19 °C, and 20, 24, and 28 °C respectively, for 2-4 weeks before swim respirometry trials began. I found that embryo incubation temperature influences the whole-animal aerobic performance of Lake Whitefish but does not affect Yellow Perch. Lake Whitefish incubated as embryos at 5 °C demonstrated a reduction in critical swimming when acclimated to 15 °C as juveniles. An interaction between the embryo incubation temperature and the response to juvenile acclimation temperature was also detected in Lake Whitefish, where the routine metabolic rate of fish incubated as embryos at 5 °C did not increase when acclimated as juveniles to 19 °C compared to 15 °C. No influence of embryo incubation temperature was observed in the whole-animal aerobic performance of Yellow Perch. My results imply that Lake Whitefish and potentially other species that demonstrate similar developmental characteristics are likely to be impacted by increases in global water temperatures. Decreases in whole-animal aerobic performance could have negative impacts on survival and recruitment. Yellow Perch and other species that share developmental characteristics will be impacted to a lesser extent. Although the mechanisms responsible for the effects of embryo incubation temperature on later life whole-animal aerobic performance are not well understood, this study gives a baseline for further research to build upon. By understanding the potential for embryo incubation temperature to influence later life whole-animal aerobic performance, future studies can be conducted to isolate the mechanisms associated.