Effects of Incorporating Validated Juvenile Otolith Microincrements on Growth Estimation and Stock Assessment of the Southern Brazilian Stock of Mugil liza

Abstract

Understanding individual growth is essential for assessing exploitation status and supporting sustainable fishery management. For the southern Brazilian stock of the mullet Mugil liza, previous growth estimates were based on whole otolith readings and included few young individuals, potentially influencing growth parameter estimation and stock assessment outputs. In this study, daily otolith microincrements of juveniles were validated using oxytetracycline (OTC) marking and combined with age–length data from a previous study to evaluate the effect of incorporating validated juvenile ages into von Bertalanffy growth function estimates. The updated model yielded a 15% smaller asymptotic length (564 mm), a 47% higher growth coefficient (0.28 yr−1), and a theoretical age at zero length closer to biologically plausible values (t0 = −0.11). Revised growth parameters were incorporated into an age-structured production model (ASPM). Although temporal trends in spawning biomass and fishing mortality remained similar, substantial differences were observed in biomass scale and biological reference points. These findings highlight the sensitivity of stock assessment outputs to growth parameterization and the importance of adequately representing early life stages in growth models.

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