Validation of annual growth increments in the otoliths of a small, tropical coral reef fish

Abstract

ABSTRACT: Three criteria were assessed to determine the usefulness of otoliths to age individuals of Pomacentrus mollucensis collected from the lagoon of John Brewer Reef on the central Great Bamer Reef between March 1988 and February 1989. (1) Otoliths. as measured along various axes, demon- strated asymmetrical growth through time, but nevertheless grew throughout the lives of the fish. (2) A total of 18 fish recaptured after treatment with tetracycline 1 yr previously, demonstrated one thin, opaque increment in the otolith structure that had formed since treatment. (3) Marginal increment analysis, while not as definitive, strongly suggested that opaque increments were formed in the austral spring, generally between September and November These 3 results indicated that opaque increments found in the otoliths of P. mollucensis are formed annually and hence can be used to determine age- specific parameters of the populations. Von Bertalanffy growth curves and age structures were derived for 3 representative samples to illustrate this point