CCAMLR

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.

At WG-SAM-2019, it was highlighted that some of the language in the table used to assess research plans in data-poor fisheries was ambiguous, in particular to delegates that do not have English as their first language. In this paper, we propose some revisions to the table to attempt to reduce this ambiguity. 

The five years of survey and observations of Dissostichus spp. in statistical subarea 48.2 on board the Ukrainian vessel SIMEIZ. Survey was conducted in accordance with the recommendations of the Scientific Committee and Commission. Data on the distribution of Antarctic toothfish and by-catch fish, biological characteristics of Antarctic and Patagonian toothfish are presented. Biomass of Antarctic toothfish is estimated using lowest over the study period CPUE rates in the 2019 season.

It  was  reported  at  WG-SAM-2019  that  the  sea  ice  concentration  (SIC) of RB 48.6-5 corresponded well with the dynamics of monthly sea surface temperature  (SST)  anomaly  in  RB  48.6-5.   However,  in  the  prediction  of SIC  in  RB  48.6-5  using  the  monthly  SST  anomaly,  there  is  a  limitation. Because RB 48.6-5 is covered by ice for almost 100% from April to October, consequently there is very little information on the SIC during this period. However, the SST of RB 48.6-2 can be used to predict the SIC in 48.6- 5.  There  is  not  a  strong  correlation  of  SST  between  48.6-2  and  48.6-5.

However there are similar SST positive spikes both in 48.6-2 and 48.6-5 and it is assumed that these are related.  This paper analyses the possibilities to predict the SIC in 48.6-5 for the following season using the daily SST of 48.6-2.

Photo-identification is a technique that uses photographs of animals to identify individuals through natural markings visible on their body and is central for research on cetaceans. Best gear configuration to conduct photo-identification consists in a SLR camera equipped with a 100-400 mm lens. This paper addresses concerns regarding the complexity and the price of the SLR gear by presenting the first trials of a cost-limited bridge camera as an alternative to no photo-identification. This bridge configuration will not match the SLR configuration, especially when animals are far from the observer but can give good results at shorter distances especially when animals are strongly marked.

Since the correlation of SST between Subarea 48.6 and Division 58.4.2 was reported in Namba et al. (WG-SAM-17/10), correlations of SIC between Subareas 48.6 and 88.1 (Ross Sea), Weddell Sea and the Sea offPeru were re-analyzed in this paper. There is some correlation of SIC between Subareas 48.6 and 88.1 with SST data from 2002-2019. In addition, the correlation of SST and SST shifted forward 6 months was analyzed and there was some negative correlation between Subarea 48.6 and the central part of the Pacific ocean. Wider phenomena such as the El Niño Southern Oscillation must influence the correlation.

In order to achieve the milestone “1.5 Update CASAL model” of the ongoing research plan submitted by Japan and France (WG-SAM19/08), the CASAL models for Dissostichus eleginoides at Division 58.4.4b were revised.

Following WG-SAM-2019 suggestions (para 6.76 in the WG-SAM2019 report), we conducted an exploration of the impact of Age Length Keys (ALK), CPUE standardization, and different scenarios of IUU on the CASAL assessment, especially B0 estimation. Furthermore, we estimated the harvest rate (CAY and MAY) as defined in CASAL manual (Bull et. al. 2012) using each CASAL runs according to WG-SAM-2019 suggestions (para 6.76 in the WG-SAM2019 report).

A single-sex age structured CASAL model was built to assess the stock of D. eleginoides at the research block 1 of Division 58.4.4b. The base model (M1) is an update the M4 model described by Okuda and Massiot-Granier (2019). It includes updated catch at age data based on annual ALKs and data sources were weighted using an automatic procedure (“DataWeighting” package, Francis 2014). In addition of this first model, three other models were tested (M2, M3 and M4), exploring both the influence of CPUE standardization and IUU scenarios on the assessment. Compared to the CASAL results reported in WG-SAM-2019/30, the MPD profiles show improvements under all scenarios to better fit the model.

Comparing the MPD profile between M1 (base model), M2 (no 2007/08 CPUE), and M3 (no season effect on CPUE), unnaturally high standardized CPUE in 2007/08 reduce 25 t B0 and difference of standardized CPUE (with/without “Spawning season” effect) cause 10% difference in B0 estimation at the block 1 of Division 58.4.4b (Table 1). Changing IUU level (26.5 t to 40 t) in 2009/10 fishing season cause increasing of B0

In all scenarios, the estimated MCYs for D. eleginoides were higher than current catch limit 19 tonnes in block 1 at Division 58.4.4b. Furthermore, harvest rates achieving the CCAMLR management target (50% B0) were estimated to be c.a. 6%. This value is higher than current precautionary harvest rate for “data-limited” explanatory/research fisheries (4%) where there is no estimate of B0.