The time series of relative abundance and age structure from the Ross Sea shelf survey provides information about year class strength, variability, and autocorrelation, and hence is an important input into the Ross Sea stock assessment.
The objectives of the survey were to (i) continue monitoring trends in Antarctic toothfish (Dissostichus mawsoni) recruitment in the southern Ross Sea (core strata A–C); (ii) continue monitoring trends in abundance of larger (large sub-adult and adult) toothfish and biological characteristics in two areas of importance to predators: McMurdo Sound and Terra Nova Bay in alternate years; and (iii) collect and analyse a wide range of data and samples from these areas (e.g., demersal fish, benthic invertebrates, stomach and tissue samples, acoustic data), which will contribute to the Research and Monitoring Plan for the Ross Sea region MPA.
The estimated relative biomass index of toothfish showed an increase to the second highest in the survey time series in 2021. Biological data and samples were collected from more than 3,100 toothfish; samples and measurements were also collected on bycatch species. A total of 268 toothfish were tagged and released with an 89.6% tagging length overlap statistic. The catch limit of 65 t was not exceeded, mainly because catches in Terra Nova Bay were lower than in previous years. Collected toothfish otoliths were aged and included in the 2021 stock assessment.