Behaviour, Energetics, and Associated Mortality of Young-of-the-Year White Perch (Morone americana) and Yellow Perch (Perca flavescens) under Simulated Winter Conditions

After 150 d of simulated winter conditions, 71.2% of the white perch (Morone americana) had died at 2.5 °C, while only 11.1% had died at 4.0 °C. For yellow perch (Perca flavescens), 0.8% had died at 2.5 °C, while 17.7% had died at 4.0 °C. For both species, small fish died first. Multiple regression models relating overwinter mortality versus fall total length and winter duration predict 3.3 times greater mortality for white perch versus similar sized yellow perch at winter temperature regimes typical of the Great Lakes region. In laboratory tanks, white perch remained active throughout the winter period, while yellow perch sought cover and rested on or near the bottom of the experimental tanks. As a direct consequence, yellow perch had a lower routine metabolic rate and consumed body energy more gradually than white perch. During their inactive wintering period at 4.0 °C, yellow perch consumed 25.8% less oxygen than white perch. Actual measurements of dry weight loss indicated that yellow perch in the experimental tanks at 2.5 °C consumed 24.6% less dry weight than similar sized white perch. These differences in overwinter behaviour, metabolism, and survival appear to be adequate to account for observed differences in survival of these species in the wild.