Improving growth estimates for Western Atlantic bluefin tuna using an integrated modeling approach

Advances in modeling growth using tag-recapture data and progress in otolith ageing procedures allowed improved fitting of the Western Atlantic bluefin tuna growth curve. Growth parameters were derived from an integrated analysis of tag-recapture data and otolith age-length data using the “Aires-da-Silva-Maunder-Schaefer-Fuller with correlation” (AMSFc) framework, which models growth such that parameter estimates from each data source are directly comparable. The otolith data consisted of a sample of 4045 otoliths for which ages were estimated using tested and consistent protocols and conventions designed to avoid bias. Strict data quality control measures were applied to the tagging data for quality assurance and a subsample of 1118 records were retained for use in the analysis. Two forms of the Schnute growth model were considered: the Richards model and the von Bertalanffy model. The Richards curve appears to provide a better fit. Both curves follow a similar trajectory until age 16, after which they diverge considerably. The Richards model supports a lower mean asymptotic length (L∞ = 271.0 cm FL) than the model currently used in the stock assessment (L∞ = 314.9 cm FL).