This paper presents an updated stock assessment for the Patagonian toothfish (Dissostichus eleginoides) fishery of the Crozet Islands, CCAMLR sub-area 58-6, with data up to the end of the season 2018/2019 (End of August 2019). This updated assessment model is based on the best available data and includes longline tag-release and tag-recapture data from 2007 to 2019 and priors and estimates on life traits model parameters (e.g. growth, maturity and natural mortality). It also uses commercial data that account for fish removals (fishing mortality and depredation) and support the estimation of their associated selectivity functions.

Compared to the previous assessment presented at WG-FSA 17 (Sinègre et al., 2017b), this assessment accounts for (1) updated data (2017/2018 & 2018/2019) (2) updated growth curve and (3) legal catches taken on the adjacent waters of Del Cano rise, outside the CCAMLR area. All model runs were conducted with the CASAL 2.30 2012-03-21 rev. 4648, that was agreed on by WG-SAM-14.

The updated model leads to smaller estimate of the virgin spawning stock biomass B0 than the one obtained in 2017, with an estimate of 54 610 tons (48 560-60 880). The estimate of the current SSB status of the stock is 63% (58.2%-66.6%) and the current catch limit satisfies the CCAMLR decision rules.

KEYWORDS: Dissostichus eleginoides, Crozet Islands, Stock assessment, Patagonian toothfish, State-space model, Population dynamic model

An observation on the interaction between marine mammal and krill midwater trawl was carried out onboard the Chinese krill fishing vessel Fu Rong Hai during the 2018/19 fishing season. The inner-trawl observation was made using an Underwater IP Camera, while sea surface observation was conducted visually with the aid of a SLR Camera and a Marine Binocular. Sea surface observation in Subarea 48.3 showed that the number of fur seal (Arctocephalus gazelle) around the fishing vessel increased from late July to August then decreased in September, and over 85% of the fur seals was observed chasing the trawl behind the codend during retrieving of the net. Although large number of Antarctic fur seal were observed at sea surface around the vessel during fishing operation, none seal by-catch was found during this fishing season and none identifiable marine mammal was observed inside the trawl either. Simultaneous observation of krill swarms detected by the echosounder revealed a linkage between the behavior of the seal and the depth of krill swarms. It is speculated that when krill swarms were available in reachable shallow depth (less than 50 m), Antarctic fur seal would feed on this krill and thereby was not attracted extensively by the presence of the fishing vessel. Chasing after the krill-filled trawl at sea surface seems to be a foraging related phenomenon.

This paper presents an updated stock assessment for the Patagonian toothfish (Dissostichus eleginoides) fishery of the Kerguelen Islands EEZ, CCAMLR Division 58.5.1. It includes commercial fishery data up to the end of the season 2018/2019 (end of August 2019). The updated assessment model is based on the best available data and includes abundance estimates from random stratified trawl surveys (POKER, 2006, 2010, 2013 and 2017), longline tag-release and tag-recapture data from 2007 to 2019 and priors and estimates on model parameters such as life traits (e.g. growth, maturity and natural mortality). It also uses commercial data that account for fish removals (fishing mortality and depredation) and support the estimation of year class strenght (YCS) and selectivity functions.

Compared to the previous assesment that was presented to WG-FSA 17 (Sinègre et al., 2017b), this assessment accounts for (1) updated data (2017/2018 & 2018/2019), (2) updated growth parameters, (3) updated priors on YCS and period of estimation. All model runs were conducted with the CASAL 2.30 2012-03-21 rev. 4648, that was agreed on by WG-SAM-14.

The updated model leads to smaller estimate of the virgin spawning stock biomass B0 than the one obtained in 2017, with an estimate of 206 200 tons (CI: 194 130 – 218 380). The estimate of the current SSB status of the stock is 60.6% (95% CI: 58.1%- 60.9%).and the current catch limit satisfies the CCAMLR decision rules.

KEYWORDS: Dissostichus eleginoides, Kerguelen Islands, Stock assessment, Patagonian toothfish, State-space model, Population dynamic model

We report on objective 2 “inform estimations of the distribution, relative abundance, and life history of the main bycatch species” of the suspended research plan on Patagonian toothfish (Dissostichus eleginoides) last submitted in 2018 by Japan and France in Division 58.4.3a (WG-FSA-18/61). We analyzed bycatch composition in number and biomass during the period 2008-2018 to investigate the inter-annual variations in bycatch patterns, spatial distribution and biological parameters of the main bycatch species. Skates (mostly Amblyraja taaf) was by far the dominant bycatch species on longlines, followed by Macrourus spp. and Antimora rostrata. Results from both captain declaration and observer reports showed strong effects of gear and bathymetry on bycatch composition and biomass. As shown in others regions, autolines were less selective than trotline. While trotlines had a bycatch-to-catch ratio of 10 to 20%, autolines ratio was up to 70% in some years. Hence, bycatch number and biomass increased strongly the years autolines operated. Skate bycatch was higher in shallower waters (900m-1200m) and the frequency of hauls with high skate CPUE led to a very high cumulated number of skates caught in 58.4.3a. While most skates were released in good or average condition and potentially survived, without more information on the post-released survival rate, we cannot rule out the fact that the use of longlines, and in particular integrated weight autolines, may have an adverse impact on skate populations in Division 58.4.3a.

We report on objective 3 “Investigate population structure of bycatch species and inform bycatch mitigation measures” of the ongoing research plan on Patagonian toothfish (Dissostichus eleginoides) conducted by Japan and France in Division 58.4.4b (WG-SAM-2019/08). We analyzed bycatch composition in number and biomass during the period 2008-2018 to investigate the inter-annual variations in bycatch patterns, spatial distribution and biological parameters of the main bycatch species. Macrourus spp., Antimora rostrata and skates (mostly Amblyraja taaf) were the three dominant species caught as bycatch on longlines. Results from both captain declaration and observer reports showed strong effects of gear, bathymetry and locations (b_1 versus b_2) on bycatch composition and biomass. As shown in others regions, autolines were less selective than trotlines and Spanish lines. While trotline has a bycatch to catch ratio of about 15%, autolines ratio was up to 70% in some years. Hence, bycatch number and biomass increased strongly in the years autolines operated. Skate bycatch was higher in the b_2 region, particularly in the eastern part, where unusually high concentrations of Pennatulacea (Sea pens) where reported in 2018. A large number of skates were caught (up to 1,400 individuals in one year). While most skates were released in good or average condition and potentially survived, without more information on the post-released survival rate, we cannot rule out the fact that the use of longlines, and in particular integrated weight autolines, may have an adverse impact on skate populations in Division 58.4.4b.

The Scientific Committee considered the assessment of Dissostichus spp. in data-poor fisheries to be of a high priority (SC-CAMLR-XXIX, paragraphs 3.125 to 3.145). The use of different gear types for the implementation of a multi-Member research on   Dissostichus spp.  in East Antarctica (Divisions 58.4.1 and 58.4.2) carried out in the seasons 2011/12 - 2017/18  is a critical factor for their   efficiency and reliability. In the context of the discussion of the Scientific Committee (SC-CAMLR-XXXVII p.3.338-3.144) related to the methodical  problems and analysis issues of  the above said research   we propose the research program on Dissostichus spp by the  multi-vessels  in Divisions 58.4.1 and 58.4.2 for seasons 2019/20-2021/22 based on standardization of sampling longline gear  and survey design.

The nomenclature or status assigned to individual toothfish fisheries in the CAMLR Convention Area is intended to be guided by CCAMLR’s regulatory framework. However, the status of toothfish fisheries and the regulatory framework has become increasingly disconnected in many fisheries throughout the Convention Area, particularly in relation to what is considered closed, exploratory and established fisheries. This disconnect has led to confusion within the Scientific Committee, Commission, and stakeholder communities. To mitigate this confusion, there is a need to realign the fishery status to be more consistent with the regulatory framework. This can be accomplished through developing and adopting a suite of triggers that specify both clear definitions and mechanisms or triggers for assigning or reassigning fishery status based on their stage of development. Here, specific examples of toothfish fisheries with a status of closed and exploratory as set out in conservation measures, and that of the regulatory framework are highlighted, along with the need to review the status of these fisheries. Some recommendations to initiate discussions on changing specific toothfish fishery status, and mechanisms to trigger this change, are provided.

Killer whale and sperm whale depredation interactions with longlines targeting Patagonian toothfish (Dissostichus eleginoides) have been documented as a severe issue in the Crozet EEZ since the late 90’s. Estimating depredation rates allows to correct catches and therefore to model the real impact of fishing activities on Patagonian toothfish stocks. Photo-identification of interacting marine mammals has been central to understand depredation and develop a mitigation scheme. Here we used photographs from the French vessels fishing in the Crozet EEZ as well as on Del Cano rise in the Southern Indian Ocean Fisheries Agreement (SIOFA), and a dataset from Spanish vessels operating on Del Cano rise. Photo-identification revealed movements of sperm whales and killer whales individuals across boundaries. Over the 2009 – 2019 period, and depredation rates were estimated to be around 8% in the Del Cano – SIOFA area.