Behavioral and Metabolic Adjustments to Low Temperatures in the Largemouth Bass (Micropterus salmoides)

Abstract

Resting metabolic rate (MR), spontaneous swimming activity, and food intake were measured in order to learn the relationship between these responses and low acclimation temperatures. The fish were collected in the fall and placed in one of eight acclimation tanks ranging from 3 to 17 C at 2 C intervals for 3 wk. Food intake was measured during and after the acclimation period, and MR and activity were measured following the acclimation period. MR, measured in a closed system, was exponentially related to temperature with a Q10 of 3.0. Food intake declined linearly down to 10 C, below which it became negligible. Spontaneous swimming activity, measured in an annular tank, was similar for all fish at or above 7 C and was considerably reduced at 5 and 3 C. These data indicate that physiological systems respond very differently to low acclimation temperatures in the largemouth bass. MR shows no compensation. The central nervous system, which mediates activity cycles, shows perfect compensation from 17 to 7 C, with a decline at lower temperatures. An energy analysis reveals that food intake fails to meet even resting metabolic requirements at temperatures below 10 C and that the net cost of spontaneous swimming activity is a small portion of the total daily energy expenditure from 3 to 17 C. The data agree well both with observations on the effects of thermal acclimation on isolated tissues and with observations made on bass in the wild.