Knowledge of recruitment dynamics, and in particular trends in recruitment and recruitment variability, are key inputs for integrated assessments of fish stocks. A quantitative longline survey monitoring the recruitment of Antarctic toothfish (Dissotichus mawsoni) in the southern Ross Sea was started in 2012. The survey was expanded in 2016 to monitor trends and biological characteristics in two areas of importance to predators, Terra Nova Bay and McMurdo Sound, and to collect data that would contribute to the research and monitoring plan for the Ross Sea region Marine Protected Area.
In most years, the survey was completed as planned, while in three years several factors have constrained the survey from sampling all stations and in the latest two seasons pandemic travel restrictions have necessitated an alternative delivery approach. Between 2012 and 2022, 2 056 tagged Antarctic toothfish have been released on the survey and 21 toothfish have been recaptured. Fifteen pop-up satellite archival tags (PSATs) were deployed on D. mawsoni in 2019 and fifteen skates were tagged in 2020 and 2021. Many tagged toothfish released from the RSSS move from the shelf to the slope. Trends in abundance indices and size and age composition consistently show the progression of strong year classes entering and leaving the survey area and have indicated that recruitment is likely more variable than previously thought. Data from the RSSS have been used to indicate year class strength in Antarctic toothfish stock assessments since 2015.
The eleven surveys to date have resulted in a substantive increase in the knowledge and understanding of the distribution and relative abundance of a range of demersal fish species and invertebrate taxa caught on the longlines. Other data routinely collected on the surveys were plankton, temperature, salinity, air quality, cetacean and other marine mammal observations, and echosounder data. The RSSS has provided synergies with other research programmes also addressing CCAMLR objectives, particularly those focused on research and monitoring within the RSrMPA.