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 by 1°C every decade. 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. Increased temperature alters the normal development of the yellow perch ( Perca flavescens), however, whether altered incubation temperature influences the development of metabolism and function in these fish remains unknown. We hypothesized that increased embryonic incubation temperature would disturb cardiac and metabolic function and the behaviour of yellow perch larvae. We reared yellow perch embryos at 12°C, 15°C, 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.