A preliminary population status model for the Patagonian toothfish, Dissostichus eleginoides, on the Kerguelen Plateau (Divisions 58.5.1 and 58.5.2) using CASAL

The Kerguelen Plateau (Statistical Divisions 58.51 and 58.5.2) supports the largest Patagonian toothfish (Dissostichus eleginoides) fishery in the Southern Ocean outside of the Atlantic sector. Analysis of genetic, demographic and tagging data indicates that toothfish form a metapopulation in this region. This paper describes the development of a CASAL model incorporating data from research, commercial and illegal fishing activities in the French and Australian EEZs. This represents a substantial step forward in understanding the dynamics and current status of toothfish across the Kerguelen Plateau. Preliminary results indicate that illegal fishing in the late 1990s and early 2000s lead to a rapid decline in stock status, however action to eliminate illegal has moderated this decline. Model fits to the substantial decline in catch rates seen in the French EEZ concurrent with illegal activities are poor, indicating that the SSB0 and stock status estimates still need to be interpreted with caution. Continuing pre-recruit surveys across the Australian and French EEZ, ageing samples from surveys and the commercial catch, and modelling tag and demographic data to better understand rates of movement and the distribution and abundance of age classes across the Plateau are suggested as part of a research program to addressing key uncertainties. Such work would enable the development of models that more fully capture the complex dynamics of toothfish throughout their life on the Kerguelen Plateau.