Influence of swimming form on otolith δ13C in marine fish

Abstract

While temperature records are available from otolith δ18O profiles in fish, interpreting changes in otolith δ13C remains ambiguous. We compiled a global database of published otolith δ 13C values for 60 species representing 30 families of marine fishes, Species' mean otolith δ13C ranged from +0.5 to -8.6‰. Among-family variance in otolith δ13C was uniquely explained by a morphometric index for aerobic swimming activity (caudal aspect ratio, r2 = 0.61). The models that consistently explained the maximum among-species variance in otolith δ13C included caudal aspect ratio and maximum depth of occurrence. Our analysis supports the use of otolith carbon-isotope ratios to indicate metabolism (primarily active) in marine fish. This information may be applied to studies of fish feeding and related food-web structure, both past and present.