Age and Growth Studies in Indian Oil Sardine ( Sardinella longiceps ) using Hard Part Microstructure, a Tool for Biological and Ecological Understanding

Age and growth characteristics of the Indian oil sardine ( Sardinella longiceps ) was studied by interpreting microstructures on hard parts. Microstructures were validated to the time scales by observing their frequency of formation on hard parts of the fishes reared in confinement. Among the hard parts, sagittal otolith alone was found suitable for ageing the species as frequency of microstructure formation on them followed definite time scale. The estimates of age at length data and growth parameters from otolith analysis indicated faster growth in the species than the earlier estimates by other methods. Despite an expected sexual divergence in their growth, results show identical growth in both sexes. It further highlighted the prevalence of very distinct temporal growth variation driven by habitat environment indicating significance of hard part studies on ecological understanding of fishes. It also aided in tracing the precise time of birth with high precision, identifying the cohorts that supported the fishery and possible inter-regional migration of the species. The data generated from hard part ageing would aid in better eco-biological understanding of species, precise stock assessment outputs and fishery forecasting.