Comparative Demography of Surgeonfishes from the Tropical Western Pacific

Surgeonfishes (Acanthuridae) are diverse and common members of coral reef faunal assemblages and are important coastal fisheries resources throughout the tropics. Life-history research provides a foundation for understanding and predicting population dynamics and is therefore important to fisheries management. However, our understanding of surgeonfish biology stems primarily from high-latitude tropical regions where they exhibit multidecadal life spans. To derive an eco-evolutionary and biogeographic perspective on the biology of acanthurids, we derived age-based life-history information for a suite of species representing over 99% of the surgeonfish fishery in the Mariana Islands. Multivariate analysis failed to provide a powerful summary of trait variation among surgeonfishes, as body size is not positively correlated with longevity, growth trajectories and length of maturation varied widely among species, and mortality is not simply a function of size or growth. In fact, seven of twelve species studied exhibited unusual biphasic mortality pattern. Different modes of reproductive investment in species appear to carry a taxonomic signature and may influence the vulnerability of some species to overexploitation. Comparisons with previous studies demonstrated a strong thermal gradient in life span and body size across latitude. Ultimately, surgeonfishes display puzzling features whereby extended life spans are uncharacteristically coupled with higher-than-expected mortality rates as a result of biphasic mortality schedules at the population level. Trait relationships among species are not straightforward, posing challenges for designing effective management and for predicting population dynamics under global climate change.