Temperature constraints on overwinter survival of age-0 white perch

We evaluated the relative importance of energy depletion and osmoregulatory stress as possible mechanisms regulating overwinter mortality of age-0, white perch Morone americana. Fish used less energy, took up more water, and had much higher mortality at 2.5 degree C than at 4.0 degree C. Mortality, energy use, and water uptake were all related to body size. Relationships of empirically derived endurance time (ET, days to 50% mortality) to body mass were allometric with weight exponents of 0.29 at 2.5 degree C and 0.77 at 4.0 degree C. Theoretically derived weight exponents were 0.82 for ET models based on starvation and 0.18 for models based on osmotic mechanisms. The theoretical and empirical models suggest that overwinter mortality of white perch is caused primarily by starvation at 4.0 degree C and by osmoregulatory dysfunction as well as starvation at 2.5 degree C.