Variability in age and size at settlement of the tropicai goatfish Upeneus trayula (Mullidae) in the northern Great Barrier Reef lagoon

Age, size and body mass at settlement for the reef fish Upeneus tragula (Mullidae) were examined among 5 sampling stations across the northern Great Barrier Reef, over time periods ranging from days to 3 yr.Increments on the sagittal otoliths were validated as daily usiny tetracycline treatment.Fish were caught in their late pelagic stage, brought into the laboratory, and those that mctamorphosed and settled to the bottom of the tank overnight were used In the study.Twenty-five samples of newly settled fish (n = 6 to 27, mean = 14, N = 345) were compared Larval durat~ons ranged from 25 to 37 d, and standard length varied similarly, ranglng from 19 to 31 mm at settlement.Wet weight ranged from 0.09 to 0.61 g.Signifrant differences In age, length and weight at settlement were found at all spatial and temporal scales.For instance, no consistent pattern in settlement characteristics was found among stations across the northern shelf, with one sample of settled fish often being significantly different in attributes from another sample from the same station a month or two later.Growth rate averaged over the whole larval period ranged from 0.55 to 1.0 mm d-' Flsh that settled larger tended to have lower growth rates than smaller fish.Patterns of increment widths throughout the larval phase were remarkably consistent among samples.However, the relationship between otolith length and fish length was found to vary significantly among samples collected within 2 mon from 4 locations.Results suggest the cautious use of back-calculation of larval sizes from otolith increment widths, and stress the underestimated importance of small-scale variation in larval growth dynamics.No evidence was found that U. tragula has the ability to delay settlement once developmental competence was attained.