Revised stock assessment of the Patagonian toothfish, Dissostichus eleginoides, in research block C of Division 58.4.4 (Ob & Lena Banks) using CASAL

Regarding the low levels of stocks of Dissostichus spp. and the high levels of IUU fishing, CCAMLR decided to close the fishery in 2002 in division 58.4.4. Since 2008 only one vessel, Shinsei maru No. 3, has conducted research fishing in accordance with a research plan submitted under CM 24-01. France notifies its wish to collaborate in this research fishery over the coming years in order to participate in the tagging program and achieve a robust stock assessment. A preliminary assessment of stock status of D. eleginoides in SSRU C was made by Japan using a CASAL catch-at-length model in 2013. During the WG-SAM-2014, two developments of CASAL assessment were presented one by France and the other by Japan. The Working Group recommended that further development of the assessment should be considered. The model has not been updated with 2014 data but six new sensitive runs have been tested to highlight the contribution of IUU catch and selectivity, data weighting methods and catch-at-age or catch-at-length data. The median MPD estimates of the initial B₀ are around 500 and 900 tons and SSB₂₀₁₃ around 400 and 900 tons depending on the sensitivity run. However, MCMC estimates were significantly higher than MPD ones for each model. There was still some evidence of lack of convergence in MCMC posterior trace. The results seem to be not yet reliable and model not yet robust to use it as a management tool this year.