Elevated temperature during rearing diminishes swimming and disturbs the metabolism of yellow perch larvae.

Temperate waters, such as the Great Lakes, are predicted to increase in temperature by 1°C every decade. Many poikilothermic fish thermoregulate behaviourally, moving to more suitable thermal environments. Embryos are incapable of locomotion and may be exposed to non-optimal temperatures during development. Previous work has suggested that temperature increases during embryogenesis can alter growth rates in fish. However, less is known of whether these early-life exposures to elevated temperatures can impart alterations to the phenotypic plasticity of performance traits, particularly in temperate species. We hypothesized that increased embryonic incubation temperature would diminish the larval performance of yellow perch (Perca flavescens), a critical cultural and ecological species of fish. We reared yellow perch embryos at 12, 15 or 18°C until hatching; after hatching, the temperature was raised to a common garden 18°C, their preferred post-hatch temperature. We assessed exploratory behaviour, metabolism (oxygen consumption) and cardiac performance throughout early development. At hatch, 12°C fish exhibited the greatest swimming activity, with 18°C fish consuming the least oxygen and possibly experiencing mitochondrial dysfunction. Cardiac development was more advanced at hatch in 18°C fish. Yet, warmer incubated fish had diminished movement and increased oxygen consumption at 20 days post-hatch, demonstrating long-term disruptions of increased temperature in the embryonic environment. Overall, elevations in rearing temperature may cause metabolic dysfunction and behavioural alterations, potentially impacting the survival of yellow perch.