The effect of early life thermal environment on morphology and growth of yellow perch (<scp><i>Perca flavescens</i></scp>)

Early life development in fishes is a period of high phenotypic plasticity. Water temperatures during embryogenesis can lead to alterations in growth and metabolic and morphological phenotypic variations. This study aimed to characterize the effects of temperature on the growth and morphology of yellow perch throughout early development, a species of significant ecological and economic importance in North America. Yellow perch (Perca flavescens) embryos were incubated at either constant temperature (12, 15, or 18°C) or under an ambient seasonal regime, where temperature increased throughout embryogenesis until it reached 18°C. All groups were gradually warmed at hatch until they reached 18°C, and morphology was assessed. Inverse relationships between temperature, length and yolk-sac volume were found at the end of the embryonic period. Optimal embryonic growth was associated with the ambient seasonal regime. Fish reared at 15 or 18°C were larger and had higher growth rates when compared to those at 12°C following hatch. However, fish reared in cooler temperatures may possess more advantageous body shapes. Surprisingly, the ambient seasonal incubation had the lowest growth rate post-hatch, even though this most closely mimicked natural incubation for this species. Because suitable larval morphology is related to survival and successful recruitment, these data suggest that yellow perch may be vulnerable to climate change and thermal pollution, although further work is needed to better predict the ecological implications of the phenotypes.