Rates of Heat Exchange in Largemouth Bass: Experiment and Model

A mathematical model of body-core temperature change in fish was derived by modifying Newton's law of cooling to include an initial time lag in temperature adjustment. This model was tested with data from largemouth bass (Micropterus salmoides) subjected to step changes in ambient temperature and to more complex ambient regimes. Nonlinear least squares was used to fit model parameters k (min−1) and L (initial lag time in minutes) to time series temperature data from step-change experiments. Temperature change halftimes (t1/2, in minutes) were calculated from k and L. Significant differences (P < .05) were found in these parameters between warming and cooling conditions and between live and dead fish. Statistically significant regressions were developed relating k and t1/2 to weight and L to length. Estimates of k and L from the step-change experiments were used with a computer solution of the model to stimulate body temperature response to continuously varying ambient regimes. These simulations explained between 52% and 99% of the variation in core temperature, with absolute errors in prediction ranging between 0 and 0.61 C when ambient temperature was varied over 4 C.