CCAMLR

In accordance with decision of SC-CCAMLR in 2010, the Russian Federation conducted research fishery on toothfish in Subarea 88.3 in the season 2010/11. The researches were carried out onboard longliner Sparta (company “Morskoi Voron”). In total, 20 trotline sets at different depths have been made, the total number of exposed hooks being 87,096. The research program covered SSRU B, C, and D of Subarea 88.3. In SSRU A longlines were not investigated because ice conditions were difficult. All toothfish catches and by-catch were subjected to biological analysis. 30 toothfish individuals of different size were tagged, size distribution of tagged fish being in accordance with the size distribution of fish of catches. Material sampled included 240 otoliths for age determination, 53 samples for genetic analysis and 42 samples for histological analysis. In total, 256 toothfish individuals were caught that corresponded to 5,230 t by weight. The detailed data on size composition, spatial and bathymetric distribution of toothfish, and its feeding in Subarea 88.3 B-D were obtained.

The Ross Sea toothfish fishery in Subarea 88.1 and 88.2A&B has been classified by CCAMLR as an exploratory fishery since 1998.  The current classification of this fishery as ‘exploratory’ has led to the widespread misconception that little information is available for this stock, and that a rigorous assessment of the stock status and estimation of long-term precautionary yield has yet to be undertaken.  In fact, many biological characteristics of D. mawsoni are now well understood, and integrated assessments using the CASAL framework have been undertaken since 2005.  Although there remain uncertainties with aspects of the stock, we propose that the stock is sufficiently well understood and assessed that it should be re-classified.  To ensure that sufficient data are acquired to continue assessment of this stock, we propose retaining several elements of the current requirements for Members wishing to participate in the Ross Sea toothfish fishery as set out in Conservation Measures 21-02 and 41-01.
 

The diet of Antarctic toothfish (Dissostichus mawsoni) and Patagonian toothfish (D. eleginoides) was examined around the south sandwich islands in the southern ocean, one of few regions with overlapping populations of the two species. Despite large differences in the proportion of stomachs containing prey (76.2 % of D. mawsoni compared to 7.2 % of D. eleginoides), diet composition was broadly similar (schoener overlap index of 74.4 % based on prey mass) with finfish (particularly macrourids and muraenolepidids) and cephalopods (mainly Kondakovia longimana) comprising more than 90 % of the prey mass of both species. Predation rates of the main fish prey, as mean counts per stomach sampled, were spatially correlated with their relative abundance around the islands derived from fishery bycatch data, suggesting a general lack of prey selectivity. This study supports the view that bathyal toothfish are opportunistic carnivores and finds that D. mawsoni and D. eleginoides occupy a similar trophic niche and are likely to compete for prey in regions where both are distributed.  However, the large increase in rate of prey occurrence and size of prey in D. mawsoni stomachs relative to D. eleginoides suggests species differences in feeding behaviour, which may reflect the increased metabolic demands of a cold water-adapted physiology.

A length-based projection model is used to estimate catch limits for the 2011/12 fishing season for Champsocephalus gunnari in CCAMLR sub area 48.3. The model is initialised using estimated numbers at length derived from survey length density and biomass density data, removing the need for cohort identification associated with age based projection models used historically. Application of the harvest control rule ensuring 75% escapement after a two year projection period yielded a total allowable catch of 3,072 tonnes for 2011/12 and 2,933 tonnes for 2012/13.

The 2011 groundfish survey took place at South Georgia and Shag Rocks on the FV Sil between the 27th January and 6th February 2011. 87 random hauls were completed, with good coverage across the shelf. Catch-weighted length frequencies of mackerel icefish indicated that 3+ sized fish dominated at Shag Rocks, however 1+ and 2+ sized fish were present in larger proportions at South Georgia. A mean biomass of 49,353 tonnes was estimated for mackerel icefish, with a lower 1-sided 95% CL of 31,373 tonnes. Euphausiidae was the dominant prey item in the mackerel icefish diet with increased dietary importance compared to 2009/2010. As seen during the 2009 and 2010 survey, icefish remained close to the bottom and very few acoustic marks were observed in the water column. Themisto sp. was the only other prey that made a substantial contribution to the diet, occurring in 39.47% of stomachs.
Catches of Patagonian toothfish were greater than in 2009 and 2010, with a large haul of 40-45cm fish (1.6t) around Shag Rocks. These fish are likely to be the same cohort that was evident at Shag Rocks in 2010 (fish were then 29-39cm age 2+).

A stock assessment of the Patagonian toothfish (Dissostichus eleginoides) at Kerguelen Island (division 58.5.1 of the CCAMLR) was undertaken with the modeling software CASAL, using different statistical and biological datasets: abundance estimation from the POKER 1 and 2 scientific cruises, catch per unit effort of the commercial fishery, tagging survey, sample size frequencies… CASAL is a simple population-modeling tool, applied to a single area and based on sex combination. The spatial complexity of the fishery is modeled using different functions for fishery selectivity depending on the fishing zone and the type of fishing vessels (trawlers, long-liners). The fishing zone for the long-liners is divided in four areas (North, East, South, Skiff Bank) and in two depth categories: less than and more than 1,500m. Commercial catches are integrated in the model by CCAMLR season. A weighted combination of datasets was integrated using the effective samples’ size calculated at the level of each haul. An iteratively estimated process error was applied to the length frequency data. With an initial biomass of about 200,000 tons, the modeling tends to present results which are consistent with the stock assessments undertaken by the Australian scientific team at Heard (subarea 58-5-2) and over the Kerguelen Plateau. The biomass long-term projection, done for the Patagonian toothfish with a simulated 5,100 tons catch by long-liners, fulfils the CCAMLR management rules. However, these results should be considered with caution and research studies aiming at collecting more biological data and getting a better understanding of the population spatial complexity should be continued.

Results of comparative histological analysis of gonads of female and male Antarctic toothfish Dissostichus mawsoni caught by Russian longliners in the Ross Ross Sea of the Pacific sector in 2004/2005 - 2006/2007 seasons are presented. Morphological indices of females and males, age, indices of gonads, fecundity, and condition by Fulton are described. The criteria of assessment of maturity stages of ovaries, cytological indices of oocytes, and the type of toothfish oogenesis are determined. It was established that in the period of fishing, females and males with gonads at maturity stage III were dominated. Ovaries contain two groups of oocytes of the period of trophoplasmatic growth and large oocytes of the nearest spawning season that comprise the smallest proportion of total sex cells. The individual absolute fecundity was 0.33 million eggs, relative fecundity –29 eggs per g. It is suggested that in the Ross Sea the termination of gonad maturity of toothfish takes place from March to April, and spawning takes place from June to August. By the histological data 7-40% females had prespawning ovaries condition, and diameter of their large oocytes was 1075 - 2331•10-6m in different years.

This paper summarises recent, fishery-related scientific research notified in accordance with Conservation Measure 24-01. Four notifications were received by the Secretariat for research in 2010/11, and five notifications have been received to date for research in 2011/12.

This paper summarises the data collection requirements for the exploratory fisheries for Dissostichus spp. and the general characteristics of the research hauls which may assist WG-FSA to determine the extent to which the available data may be used in developing assessments for these fisheries.

This paper summarises the data collection requirements for the exploratory fisheries for Dissostichus spp. and the general characteristics of the research hauls which may assist WG-FSA to determine the extent to which the available data may be used in developing assessments for these fisheries.