CCAMLR

A preliminary assessment is undertaken to increase the knowledge of the Patagonian toothfish (Dissostichus eleginoides) stock in Crozet area. This study is based on a CASAL (C++ Algorithmic Stock Assessment Laboratory) model. Different statistical and biological datasets are used: catches, tag releases/recaptures data, commercial catch-at-length data and Killer whales impact. Preliminary results show different estimates for the initial and current biomass. A range of 55000 to 115000 tons is observed for B0 estimates and SSB never fall below 70% of the initial biomass considering the actual level of catches.
 

In 2011/2012, a French vessel conducted its first exploratory fishery for Dissostichus spp. in division 58.4.3a. A new campaign is scheduled for 2013. France has also notified its intention to participate in this exploratory fishery over the next three years in order to achieve a robust stock assessment that would provide advice on catch limits according to CCAMLR decision rules. This paper aims to present a research plan for 2013/2014 that takes into account the remarks made during the WG-FSA 2012 and to progress on modeling tools in order to improve the estimation of current biomass. An update of the assessment of Dissostichus eleginoides using a CASAL model and a simple Petersen biomass estimate derived from tagging data are presented. The CASAL model structure used for a preliminary assessment of the stock in 2012 has been retained and updated with a small number of changes to try to improve the fit of the model. B₀ is estimated at around 1,400 tonnes and B₂₀₁₃/B₀ at around 85%. Sustainable yield, calculated in accordance with the CCAMLR decision rules is around 70 tonnes for D.eleginoides whilst sustainable yield calculated from the Petersen biomass estimates and application of the gamma value (0.038 determined for toothfish in Subarea 48.4) was 21 tonnes. As further work is required to provide management advice, the catch limit of 32 tonnes for 2012/2013 is suggested.

In response to a request from WG-SAM, the secretariat inspected the available data on toothfish within-season recaptures (i.e. fish that have been tagged and recaptured in the same fishing season). Despite short times at liberty, the frequency distribution of distances between tag and recapture locations for these fish was similar to that of all recaptured fish. The relative frequency of within-season recaptures varied spatially and a particular ‘hot-spot’ was found over a northern, and isolated, seamount in Subarea 88.2.