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.