Age Structure and Growth of the Dusky Damselfish, Stegastes Fuscus, From Tamandaré Reefs, Pernambuco, Brazil

Age structure and growth of Stegastes fuscus were investigated during the present study. Individuals were collected monthly by divers using nets and spears in the reefs off Tamandare, Pernambuco, Brazil. Otoliths were removed from 346 individuals and sectioned transversally to determine individual age. Otolith sections showed a clear pattern of opaque and translucent bands. Opaque bands were counted and initially attributed to the age of individual fish. To determine the periodicity of band formation, a validation experiment was performed, in which individuals (n = 8) were injected with tetracycline (50 mg kg-1) and kept in the laboratory for periods of three months to one year. Results of the validation experiment showed that one opaque band is deposited per year. The age of individuals collected from January to December 1995 ranged between 0 and 15 years. Analysis of margins of monthly collected individuals suggested that opaque bands are deposited during the dry season, between September and March. Readings of tetracycline-marked otoliths corroborated these results. The length-at-age curve yielded a growth constant (K) of 0.19 y-1. The high variability of the length-at-age data indicated high variability in individual growth. Length–frequency data were also used to obtain growth parameters. The growth constant, as determined with these data was 0.6 y-1 and differed markedly from K values determined from length-at-age data. It was concluded that length-frequency data are not suitable to determine growth of this species. The present study showed that otoliths are a reliable structure for aging S. fuscus, which showed to be a relatively long-lived and slow-growing tropical reef species.