Largemouth Bass Weight Loss during Winter: Experiments and Bioenergetics Simulations

A series of laboratory experiments was conducted to measure individual weight loss during 8-12 weeks of starvation under simulated winter conditions for age-2, age-1, and age-0 largemouth bass. Grand mean daily temperatures were 3.8°C, 3.2°C, and 4.0°C in winters of 2009, 2010, and 2011, respectively.  Smaller fish lost a larger percentage of their initial body weight during winter starvation.  After 12 weeks, age-2 fish lost 4.3±0.7% of initial 516.8 g; age-1 fish lost 6.6±0.3% of initial 33.2 g.  After 8 weeks in winter of 2010, 14 age-0 fish had died; four survivors lost 11.9±1.9% of initial 2.2 g.  After 10 weeks in winter of 2011, age-0 fish lost 11.1±2.5 % of initial 5.1 g. Final percent dry weight was not significantly different from an initial sample (age-2 fish: 28.8±1.2%; age-1 fish: 22.6±0.2%; age-0 fish: 21.6±0.1% in 2010 and 22.2±1.4% in 2011).  Bioenergetics simulations of these experiments over-predicted weight loss during winter until the Wisconsin model respiration rate was multiplied by 0.19 or the Rice et al. model respiration rate was multiplied by 0.077.