Age, growth, mortality and reproduction of the blackspot snapper, Lutjanus fulviflamma (Forsskål, 1775), in the southern Arabian Gulf

Abstract

The population dynamics and reproductive biology of Lutjanus fulviflamma were investigated using biological and size-at-age data derived from regular monthly samples of commercial catches in the southern Arabian Gulf. Transverse sections of sagittal otoliths showed well defined structural increments consisting of alternating translucent and opaque bands which were validated as annuli. The maximum absolute age estimates were 12.8 yrs (males) and 14.3 yrs (females). The size-at-age relationships were highly asymptotic in form with the majority of growth being achieved by the second year beyond which there was little increase in size with age. There were differential growth characteristics between sexes with females increasing in size with age at a faster rate and growing to a significantly greater mean size-at-age than males. Fish were observed in spawning condition between April and July, and the mean sizes and ages at first sexual maturity were 16.7 cm L F (1.6 yrs) for males and 18.7 cm L F (1.9 yrs) for females. The relatively short lifespan, rapid initial growth, early attainment of sexual maturity and high natural mortality rate, suggest that unlike most of the larger Lutjanids, L. fulviflamma would be resilient to exploitation. Furthermore, the study demonstrates the utility of structural increments in sagittal otoliths as a foundation for age based approaches to the assessment of fisheries resources in the southern Arabian Gulf.