We provide an update of the Bayesian sex and age structured population stock assessment for Antarctic toothfish (Dissostichus mawsoni) in the Ross Sea region (Subareas 88.1 and SSRUs 88.2A–B), using catch, catch-at-age, and tag-recapture data from 1997–98 to 2014–15 and including the results from the Ross Sea shelf survey from 2012 to 2015. The model results were similar to the 2013 assessment suggesting that recent tag-recapture and proportion-at-age observations were consistent with previous observations. Sensitivity runs showed that the results were relatively insensitive to the use of logistic selectivity ogive, inclusion/exclusion of quarantined data, and restricting tag data to the most recent six years.
Model runs showed that the data from the Ross Sea shelf survey were required to reliably estimate relative year class strengths. Year class strengths were estimated from 2003 to 2009 and showed one strong year class and two weak year classes.
Overall, model fits to the data were adequate, and, as in previous assessments, the tag-release and recapture data provided the most information on stock size. Monte-Carlo Markov Chain (MCMC) diagnostics suggested no evidence of non-convergence in the key biomass parameters. The precautionary yield, using the CCAMLR decision rules and current relative catch distribution between the shelf, slope, and north areas of the Ross Sea region, was either 2855 t or 2870 t from the two reference case model runs R1 and R2.