Variation in the population biology of stripey bass Lutjanus carponotatus within and between two island groups on the Great Barrier Reef

Density, population structure, mortality and growth of Lutjanus carponotatus on the Great Barrier Reef were compared on 2 spatial scales: between the Lizard and Palm Island groups and among 4 locations within the Palm group. The mean density at the Palm group was approximately 7 times that of the Lizard group. There were 2-fold differences in density within the Palm group, but strong statistical signals were not detected due to high variability in the data. Differences in size structures and asymptotic body sizes between the island groups were pronounced, and smaller differences were also evident within the Palm group. While age structures were similar among Palm group locations and lacked anomalous peaks, a series of strong cohorts at older age classes at the Lizard group suggests greater recruitment variability there during the past 2 decades. Variability in mortality did not increase with scale, as larger differences existed within the Palm group than between it and the Lizard group. The population traits estimated in this study were used in conjunction with reef area data to generate estimates of abundance and biomass, the values of which illustrate how multiple population traits interact to ultimately determine population size and reproductive potential. Multi-scale studies that examine a variety of aspects of population biology are rare for large reef fish, but are needed to identify which traits are likely to exhibit variation on which spatial scales.