Relationship between ontogenetic changes in foraging ecology and muscle lactate dehydrogenase activity in wild smallmouth bass (Micropterus dolomieu)

Abstract

The activity of muscle glycolytic enzymes scales positively with body size in active fish, a phenomenon thought to counter the increased costs of burst swimming faced by larger individuals. Recent work argued that changes in these enzymes during ontogeny additionally reflect changes in foraging ecology. Here, we evaluated the relationship between muscle anaerobic metabolism and foraging ecology in a population of wild smallmouth bass (Micropterus dolomieu) by relating activity of muscle lactate dehydrogenase (LDH) to estimates of trophic position and habitat use obtained from stable isotope signatures. As expected, LDH activity increased with body size. However, further analysis showed associations between foraging ecology and LDH activity. Specifically, a shift to higher trophic position, indicating a change in diet, was paralleled by a shift to increased LDH activity. However, a steady mass-specific decrease in LDH activity was observed as the fish grew above the size associated with this diet shift. Further, lower LDH activity was associated with increasing use of littoral carbon sources. These findings contribute to our understanding of how plasticity in muscle anaerobic potential is associated with fish foraging ecology.