CCAMLR

Movement of Patagonian toothfish in Subarea 48.3 was investigated using tagging program data.  Data from 33,322 tag releases and 4,203 tag recaptures were used.

The mean movement rate of both sexes combined varied from 25 to 34 km year^-1.  There was no significant difference in movement rate between male and female fish of the same maturity category.  Male and females with developed, ripe and spent or resting gonads had significantly lower movement rates than immature females.

There was significant negative positive correlation between movement rate and local toothfish density at the point of release.

This work is based on material from Antarctic toothfish, collected in the Ross Sea from December 2004 to March 2005 on the longliner “Volna”.  Age was determined for 364 individuals. Currently widely applicable "the break and burn method" was used in the present work (Chilton, Beamish, 1982; Penttilla, Dery, 1988). According to the method, otolith is broken into two parts across the core.  All in all 6009 specimens of toothfish were aged using the same above described method. Otoliths were collected by Russian observers aboard longline vessels at the Ross Sea during 2002-2007 seasons. We consider the used method is appropriate for mass age determination for toothfish.

A tagging survey in SSRUs B and C in Division 58.4.4 a & b was conducted in the 2011/12 fishing season with the aims of providing the data required for assessments of the population structure, size, movement and growth of Dissostichus spp. in the centred area of Division 58.4.4 a & b. An approximate stock biomass level of Dissostichus spp. in the survey area was tentatively estimated using simple Petersen and CPUE comparison methods. The medial estimate using simple Petersen (3 062 ton) was larger than that (1 928 tonnes) estimated in the WG-FSA meeting in 2011 (SC-CAMLR XXX, Annext 4, paragraphs 5.19-21), although the 95 % confidence intervals were wide due to small numbers of recapture. CVs of 20 % achievable from Petersen biomass estimates may be achieved within three years with an annual research catch of approximately 55 tonnes. The estimate (1 086 tonnes) using CPUE comparison method was a third smaller than that using simple Petersen. The catch biomass level was calculated as 153 tonnes using simple Petersen and 54 tonnes using CPUE comparison at 5 % of exploitation rate. From these results the proposed sample size as existing 70 tonnes for the next 2012/13 survey seems to be appropriate. However, it should be noted that one of the reasons for small number of recaptured fish and decreased CPUE in 2011/12 may be due to depredation by killer whales (see details in the simultaneously submitted WG-SAM-12 report on the results). Thus, the catch biomass estimate using simple Petersen may be overestimated, while that using CPUE comparison may be underestimated. We propose to continue the mark-recapture experiment in SSRUs B and C in the 2012/13 season with slightly modified designs, considering security of operation, effective capture and high tagging performance. To apply mark-and recapture studies, tagging rate of ≥ 5 fish / ton will be conducted. The comparison test with the experimental gear, which consists of three segments of Trot line system and Spanish line system respectively, will be conducted at 14 hauls, due to understanding of differences in the physical and hooking conditions of tagged fish between those caught on Spanish lines and those caught on trotlines.

A survey was conducted in order to collect information for the stock status and various biological information on toothfish in Division 58.4.4a & b (Ob Lena Bank) by using a commercial bottom longline vessel, Shinsei Maru No. 3, from April 15 to May 19, 2012. This report described the results during the survey in two SSRUs (B & C) of Ob Lena Bank. Total catch (excluding tagged and released fish) of Dissostichus eleginoides was 28.3 tonnes in the survey area in 70 longline sets, contributing 91.3 % to the total fish catch (31 tonnes). Mean CPUEs of D. eleginoides was in the SSRUs were 6.7 indiv. / km (CV = 70.0%) in terms of number and 48.3 kg / km (CV = 79.1%) in terms of weight. The mean CPUE in terms of weight in SSRU B (32.1 kg / km) was rather lower than that (50.5 kg / km) in the same SSRU in 2010/11. A total of 172 individuals of toothfish with good physical condition and single-hooked were tagged and released during the survey, and 3 D. eleginoides, which were tagged and released in SSRUs B and C from the 2007/08 to 2010/11, were recaptured in the same SSRUs, respectively. The overlap of size between the fish released with tag and that of overall catch was high (θ=81 %). Fish with good physical condition and single-hooked contributed 50 % to the total among fish caught by Spanish line system, while this kind of fish contributed 14 % to the total among fish caught by trotline system. A total of 133 killer whales (Orcinus orca) were observed at the 30 hauls. All of whales observed and the predatory damaged toothfish occurred in SSRU B.

The vessel tried to avoid killer whales as in the previous surveys but could not escape from them effectively in SSRU B. The depredation may lead to underestimate of nominal CPUE and rather small number of recaptured fish until now in this SSRU.

Research plan for the exploratory longline fishery for Dissostichus spp. in 2012/13 for France in Division 58.4.3a.

Research plan for the exploratory longline fishery for Dissostichus spp. in 2012/13 for Spain in Divisions 58.4.1 and 58.4.2.

Research plan for the exploratory longline fishery for Dissostichus spp. in the 2012/13 season for South Africa in Subarea 48.6 and Divisions 58.4.2 and 58.4.3a.

Notification for multi-year research in Subarea 48.5.

Research plan for the exploratory longline fishery for Dissostichus spp. in 2012/13 for Korea in Division 58.4.1.

Research plan for the exploratory longline fishery for Dissostichus spp. in the 2012/13 season for Japan in Subarea 48.6 and Divisions 58.4.1, 58.4.2 and 58.4.3a.