Patterns of annual increment formation in otoliths of pomacentrids in the tropical western Atlantic: implications for population age-structure examination

Only recently have managers and scientists begun to collect age and growth information necessary for effective management of tropical marine ichthyofaunal communities. The majority of studies that have taken place in the tropics have focused on the Pacific Ocean, primarily on Australia's Great Barrier Reef. In this study, otoliths were collected from 2 pomacentrids at 5 locations in the tropical western Atlantic, and examined for their ability to provide information on age. The collection sites for these 2 species, Stegastes planifrons and S. partitus, represent different ranges of annual temperature variation. Otoliths were examined for the presence of clear and interpretable increments as well as timing of increment formation. Annual increment quality varied between species and between regions, with the trend being decreasing clarity with decreasing temperature range, However, interpretable increments were discovered in areas with as little as a 3degreesC annual water temperature fluctuation. Marginal increment analysis of S. planifrons otoliths revealed that increments formed on the otoliths were deposited once a year during the spring or early summer, suggesting that pomacentrids in the tropical western Atlantic may be aged using the same techniques as in other tropical regions and temperate environments. Counts of annual increments revealed that S. planifrons was significantly longer-lived than predicted by other methods. Information on age and growth collected for reef fishes in studies such as this should provide managers with the life-history information needed to assess population stability and production. This information will be more difficult to obtain in low-latitude regions of the tropical western Atlantic.