Do biochemical indices of aerobic capacity correlate with swimming speeds of kawawkawa tuna (Euthynnus affinis) and chub mackerel (Scomber japonicus)

Previous research has shown that biochemical indices of aerobic metabolic capacity in locomotor muscle increase with general activity level and with resting oxygen consumption rate in fishes. From this work, generalizations about the relationship between tissue biochemical characteristics and fish aerobic performance have been made, even though locomotor performance and fish activity have not been quantified. The purpose of this study is to test the hypothesis that muscle aerobic capacity in kawakawa tuna ( Euthynnus affinis) and chub mackerel (Scomber japonicus) correlates with fish maximum sustainable swimming speed (Ucrit) or VO 2 measurements. Three biochemical indices of aerobic capacity were measured in red and white myotomal muscle and heart: specific activities of the enzymes citrate synthase (CS) and 3-hydroxy-o-acyl-CoA dehydrogenase, and myoglobin concentration. Significant positive correlations were found between red muscle CS activity and myoglobin concentration with Ucrit and VO2. However, these correlations can best be explained by covaration with fish size.