Relationship between Body Size and Anaerobic Metabolism in Brook Trout and Largemouth Bass

Abstract

The relationship between body size, anaerobic capacity, and white muscle acid-base and metabolite status was examined for two sizes of brook trout Salvelinus fontinalis and largemouth bass Micropterus salmoides. Resting muscle lactate, pH, HCO3−, and partial pressure of carbon dioxide (Pco2) were size-independent in brook trout. After exercise, however, there was a significant positive relationship between the accumulation of both lactate and metabolic protons and body size in brook trout. In addition, there was a significant size-dependent decrease in postexercise muscle pH, with larger trout experiencing a more severe drop in muscle pH. In contrast, the postexercise changes in muscle HCO3− and Pco2 remained size-independent in trout. Having observed that anaerobic capacity (i.e., lactate production) apparently was affected by body size in trout, we measured the concentrations of two other anaerobic energy reserves—phosphocreatine (PCr) and ATP—in trout white muscle before and after exercise. Under resting conditions, large trout possessed greater concentrations of both ATP and PCr than smaller trout. After exercise, the levels of ATP and PCr decreased in all trout but were size-dependent and size-independent, respectively. Under resting conditions, muscle lactate, pH, HCO3−, and Pco2 remained size-independent in largemouth bass. After exercise, white muscle lactate and metabolic proton concentrations increased and pH decreased in all bass; however, in contrast with brook trout, none of these variables were significantly related to body size. The results of our in vivo experiments therefore agree with the previously documented in vitro relationships between body size and glycolytic enzyme activities in different species of fish. In addition, these results may be important for fisheries management issues, such as catch-and-release fishing.