Allometric scaling of maximal enzyme activities in the axial musculature of striped bass, Morone saxatilis (Walbaum)

It had been suggested that the activity of anaerobic enzymes in the white muscle of fish increases exponentially with body size to meet the increasing hydrodynamic costs of burst swimming. We tested whether this relationship holds across a very large size range of striped bass, spanning a nearly 3,000-fold range in body mass. We examined the scaling of marker enzymes of anaerobic (lactate dehydrogenase and pyruvate kinase) and aerobic (citrate synthase and malate dehydrogenase) metabolism in the red and white locomotor muscles. In white muscle, we found positive scaling of anaerobic enzymes only in smaller fishes. Positive scaling of anaerobic enzymes was not found among the samples that included fishes >1,000 g despite having a sufficiently large sample size to detect such scaling. The absence of positive scaling in the white muscles of large bass suggests that they are unable to generate sufficient power to sustain relative burst swimming performance. Enzymes from aerobic pathways had activities that were mass independent in both red and white muscle. Red and white muscles were metabolically distinct except among the smallest fishes. Among young of the year, the anaerobic capacity of red muscle approached that of white muscle and also showed positive scaling. This unusual pattern suggests that red muscle might augment white muscle during burst swimming and add to the total power generated by these small fish. Maximizing burst swimming performance may be critical for small fishes vulnerable to predation but unimportant for large fishes.