Demography and age structures of coral reef damselfishes in the tropical eastern Pacific Ocean

Abstract

Few studies have examined spatial variation in the demography or age structures of coral reef fishes. We analysed sectioned sagittal otoliths to describe the age structures, growth and mortality of 5 species of Stegastes damselfishes. These were sampled at localities near the centre (Panam) and at the northern (Baja California) and southern (Galpagos) edges of the eastern Pacific tropical reef environment. Widespread damselfishes were sampled at Panam and Baja (S. flavilatus) and at Panam and the Galpagos (S. acapulcoensis). The 3 remaining species were endemic to the Galpagos Archipelago (S. arcifrons, S. leucorus beebei) and Baja California (S. rectifraenum). We found that populations of widespread species in the Galpagos and Baja grew to larger adult sizes, had relatively long life spans and lower rates of mortality once asymptotic mean sizes were attained than populations of the same species in Panam. These characteristics of long adult life spans and low mortality rates were shared by endemic species in the Galpagos and Baja. Our analysis revealed strong year classes that corresponded to the timing of El Nio-Southern Oscillation events in the age structures of both a widespread and an endemic species in the Galpagos Archipelago.