South Africa and Japan have revised the next season’s (2016/17) research plan in Subarea 48.6 using the latest CCAMLR C2 and Observer data, following several advices during WG-SAM meeting in 2016.

We have used extracted data provided by CCAMLR Secretariat in this late August for the current analysis, but not used the cleaning data provided by them in this early September due to tight schedule toward the submission.

We investigated the biological features of D. mawsoni in the Subarea and adjacent data- poor fisheries using latest Observer data. The geographical distribution of sizes, GSI and Fulton’s condition factors for D. mawsoni in Subarea 48.6 suggest that northward spawning migration and southward feeding migration as Ross Sea stock as suggested in the previous reports. Life history seems to be related to the Weddell gyre system from the location, but the larvae dispersion model previously reported does not support this hypothesis. However, some immature and mature fish from around Subarea 48.4 and juveniles from around west of Prydz Bay regions are speculated to migrate to Subarea 48.6 and be important resources for the population. The survey using the satellite tags along with analog tags is necessary in order to identify an appropriate stock unit in the future.

The stock sizes for research blocks were estimated using the Chapman estimator, the CPUE analogy method and preliminary CASAL models. We divided the two areas for block 48.6_2 by latitude of 55.2°S to estimate the biomasses of D. mawsoni because the recaptures were concentrated in the southern area. We considered that recaptures for 3 years at liberty is effective to estimate the appropriate biomass for D. mawsoni in the blocks following the recommendation in WG-SAM meeting in 2016.

Predicted numbers of tag recaptures from the estimated stock sizes using Chapman were relatively consistent with the observed numbers for D. mawsoni in the southern area of block 48.6_2, and blocks 48.6_3 and 48.6_4. However, the predicted numbers using the CPUE analogy method were generally inconsistent.

In WG-FSA meeting, we propose the sample sizes in each current research block for the next season generally based on precautionary exploit rate of 4 % of the Chapman estimates. In addition, Japan will present the preliminary proposals on appropriate shifting of the current research block 48.6_2 and will examine suitable shelf area to elucidate the stock structure under the optimum sea-ice conditions in the Subarea and adjacent waters from the 2017/18 season survey.

At its annual meeting in 2016, WG-EMM recalled its obligation to review and advise on Conservation Measure 51-07, which is due to lapse at the end of the 2015/16 fishing season, and presented its discussions on this subject in paragraphs 2.201 to 2.244 of its WG report.  WG-EMM recommended that work be undertaken to further develop a risk assessment approach to spatially subdivide the trigger level through an e-group and to deliver these outputs to Scientific Committee.  The risk assessment approach for subdividing the trigger level in CM 51-07 aims to minimise the risk to predator populations, in particular land-based predators, of being inadvertently or disproportionally affected by the krill fishery.  It also takes account of the desirability of different areas to the fishery and for management.  The overall risk of localised effects on predators can also be calculated for a known or nominated distribution of catches across the region.  It can be used to compare alternative fishing patterns in order to help minimise risk.  For example, the overall risk could be reduced by spreading the fishery further, creating buffer zones or having seasonal closures to minimise overlap between predators and the fishery at critical times.  This paper provides the first part of a contribution to the required review of CM51-07 in 2016 and provides a risk assessment method for distributing the trigger level to reduce the risk of disproportionate effects on predators in local areas.  It also provides the data to be used in the risk assessment.  The assessment and results are presented in a second paper. 

Closed mostly within the Weddell Sea Subarea 48.5 is one of the closed data-poor CCAMLR subareas, where stock assessment should be carried out. In spite of hard ice conditions at most part of the Sea during mostly all the year, this large water area is very similar to the Ross Sea. This similarity could be found in geographical location, bathymetric profile, currents system and follows from results of the first and the second stage of this program. It highlights the Weddell Sea as one of the most promising area for exploratory fishery of Dissostichus sp. However, fishery in Subarea 48.5 is closed on the basis data on stock assessment absence. The main objective of the present program is collecting data for reliable stock assessment and following estimation of precautionary limits in accordance with CCAMLR decision rules. The program contains schedule and research program of the third stage of the Russian multi-year research program in the Weddell Sea that is prospected for 3-5 years. Detailed plan of fishing operations, data collecting and analysis will be provided for the Scientific Committee and Commission consideration.

The indices of exploratory toothfish fishery in the Ross Sea for the period of 2008-2015 are considered. The analysis was focused on CPUE toothfish (kg/1000 hooks), by-catch CPUE (kg/1000 hooks) and normalized target catch ratio. There was evidence of distinct differences in the mean (and distribution) in the CPUE toothfish and the by-catch CPUE.    

Our analysis also show that target catch ratios significant varied across years and by SSMU and among longline gear types.  The spatial-temporal heterogeneity in toothfish and non-target species distribution in the Ross Sea, but not the longline vessels and  the flag States,  should  be considered  as the primary cause of the observed variability in the target catch  ratio in the Ross Sea. The observed influence of the longline gear types  (Autoline, Trotline and the Spanish longlines) on CPUE  and the target catch rations, apparently, point out varying catchability (or  efficiency)  among longline  gears both in relation to  toothfish and non-target taxa.

In order to improve the estimates of by-catch in the Ross Sea in the context of achieving the objectives of the CCAMLR Article II the following activities are proposed: investigations of spatial-temporal heterogeneity in tooth fish and non-target fish distributions through research programs the Ross Sea, as well as preparation of instructions for standardized-based   fishery data collecting and recording   onboard vessels.

Three species of skate, Bathyraja eatonii, B. irrasa and B. murrayi, are commonly taken as incidental by-catch in Patagonian toothfish (Dissostichus eleginoides) longline and trawl fisheries, and the mackerel icefish (Champsocephalus gunnari) trawl fishery on the Kerguelen Plateau (KP) in the southern Indian Ocean. Data from fishery observations for 1997 to 2014 shows that the three skates were widely distributed across the Kerguelen Plateau, showing different spatial distributions, linked mainly with depth. Off Heard Island and McDonald Islands (HIMI), in the southern part of the KP, B. eatonii and B. irrasa were most abundant to the north and northwest of Heard Island, out to the edge of the Australian Exclusive Economic Zone, and were caught down to depths of 1790 m and 2059 m respectively.  The smallest species, B. murrayi, occurred mainly in the shallower waters down to 550 m, and was most abundant to the north and northeast, close to Heard Island. Around Kerguelen Islands, in the northern part of the KP, skates were most abundant between the 500m and 1000m contours circling and extending from the islands.

Catch rates were modelled using zero-inflated GAMs and GLMs. The catch rates of skates from the trawl fisheries in the Australian EEZ surrounding Heard Island and McDonald Islands have shown little evidence of depletion on the main trawl fishing grounds, although there is evidence of a decrease in the average total length of B. eatonii.  The marine reserves and the conservation measures employed by the Commission on the Conservation of Antarctic Marine Living Resources in the HIMI fisheries, appear to provide effective protection for the skates, at least in the shallower waters where the trawl fisheries operate. B. irrasa taken in the deeper waters where longline fishing occurs have shown a slight decline in catch rate over the years of the HIMI fishery. Although all skates are returned to the water from this fishery, survival rates are unknown and careful monitoring should continue to assess the status of these stocks. There appears to be little change in the abundance of the skate species at Kerguelen in the time period.

This study provides the first review of skate by-catch across both the HIMI and Kerguelen fisheries. Ongoing monitoring of species specific by-catch levels and further research to determine the important life history parameters of these species are required, particularly for B. irrasa which is taken in both trawl and longline fisheries.