Bayesian estimation of the age and growth of the round stingray (Urobatis halleri) in the Gulf of California in Mexico

Abstract

Life-history studies of species discarded in fisheries are a low priority, particularly those of age and growth estimation. Consequently, almost everything is unknown about such species despite their having been caught as bycatch over the long term. In this study, age estimates were obtained by using the vertebrae of round stingrays (Urobatis halleri). We fitted 3 different growth models (von Bertalanffy, Gompertz, and logistic) to length-at-age data. Bayesian estimation of the various growth parameters was done by using the Markov chain Monte Carlo algorithm. Prior distributions of the parameters disc width at birth (DW0) and the theoretical maximum disc width (DW∞) were included and considered informative. The priors for the growth coefficient (k) and the completion growth parameter (k2) were set as noninformative (k for the von Bertalanffy growth function and k2 for the Gompertz and logistic growth models). Results of our analyses indicate that growth bands are annual and that the round stingray lives up to 8 years. According to the Watanabe–Akaike information criterion for model selection, the von Bertalanffy growth function for sexes combined was selected as the best model. The mean values of marginal posteriors were as follows: DW0=9.52 cm (95% credible interval [CI]: 9.25–9.79), DW∞=32.50 cm (95% CI: 30.60–34.46), and k=0.114 year−1 (95% CI: 0.101–0.129).