Predicting How Winter Affects Energetics of Age‐0 Largemouth Bass: How Do Current Models Fare?

During the first winter of life, loss of energy reserves as a function of low feeding activity and scarce prey may contribute to high mortality of age‐0 largemouth bass Micropterus salmoides. To explore how two current bioenergetics models predict winter energy depletion, we quantified growth and consumption by age‐0 largemouth bass from Alabama, Ohio, and Wisconsin fed maintenance rations in 55‐L aquaria in three simulated winters mimicking temperatures and photoperiods at low temperate latitudes (Alabama; 33°N), middle latitudes (Ohio; 40°N), and high temperate latitudes (Wisconsin; 46°N). We compared observed growth in aquaria with that predicted by putting observed consumption into both models. During winter 1995–1996, we validated one of the models with a separate pool experiment (5,800‐L) in which age‐0 largemouth bass were fed either at 0.5 × or 1.5 × maintenance ration. In aquaria, energy density of the largemouth bass declined in the high‐ and middle‐ but not in the low‐latitude winter. Though error was slight in the low‐ and middle‐latitude winters for one of the models, both models underestimated growth in the high‐latitude winter. To fit the model to the data, the function that estimates weight‐specific resting metabolism had to be reduced by about 16%. In pools, where we predicted consumption from observed growth, the model adequately predicted consumption by largemouth bass fed 1.5 × maintenance, but overestimated consumption by 0.5 × maintenance individuals. Current bioenergetics models perform poorly at the cold temperatures (<6°C), photoperiods, and low prey abundances typical of high‐latitude lakes, likely because metabolic costs are overestimated.