Growth and longevity in acanthurid fishes; An analysis of otolith increments

Abstract

Increments in the sagittal otoliths from 10 species of acanthurid fishes from eastern Australian coral reefs were used to estimate age. The species included representatives of 5 genera: Acanthurus lineatus, A. olivaceus, Ctenochaetus striatus, Zebrasoma scopas, Nasa brevirostris, N. hexacanthus, N. tuberosus, N. unicornis, N. vlamingii, and Prionurus maculatus. Systematic increments consisting of alternating opaque anti translucent bands were observed in the sectioned sagittae of all 10 species. Regression of numbers of increments on sagittal weights revealed consistent linear relationships between these variables in all species examined indicating continuous growth in sagittal thickness over the life span. For A. lineatus, A. olivaceus, C. striatus and Z. scopas recapture of specimens injected with tetracycline confirmed an annual pattern in increment formation with an opaque band being formed in early austral summer. Size at age plots revealed consistent growth patterns and life spans. All species examined had life spans of 30 to 45 yr in which rapid initial growth over 3 to 4 yr was followed by extended periods of asymptotic growth. In these species up to 80% of linear growth was accomplished in the initial 15% of the life span. Analysis of otoliths from the 5 species of Nasa and P. maculatus, while not validated, revealed similar increment distributions within the sagitta, similar relationships between increment number and otolith weight, and similar size at age plots. Acanthurid fishes from eastern Australia appear to have consistent patterns el growth and longevity despite marked differences in asymptotic size, diet and mode of life.