CCAMLR

On the basis of the bottom trawl surveys carried out by Russia and Great Britain during 2000, 2002, 2004 in the South Georgia area, it is demonstrated that the method by Aitchison and bootstrap method result in different estimates of mean fish density in the length series. Verification of the hypothesis of non-zero observations lognormal distribution for a large number of length groups casts doubt on the correctness of the first method application and therefore also of the method by de la Mare commonly used by CCAMLR in icefish age composition of abundance indices determination. To solve this problem it may be proposed to apply the modern version of the method by MacDonald and Pitcher. The comparison of this method and the method by de la Mare for length series, estimated with Aitchison’s method, were carried out. The results appeared very similar. The method by MacDonald and Pitcher has been tested on the length series obtained with the bootstrap method on the basis of the above mentioned surveys data. To estimate the standard error of the mixture distribution parameters, the “jackknifing-after-boostrap” method was proposed.

During the feeding period icefish aggregations are confined to a frontal zone between opposite flows (coastal circumfluent current and ACC) or formed inside quasistationary circulations, where the largest aggregations of food organisms are concentrated at the beginning of the spring period. Icefish concentrations were detected at the periphery of a cyclonic meander or in the centre of the anticyclonic circulation formed by the Weddell waters. Confinement of the fish to the boundary of water masses between the shelf waters and ACC was also traced. Favourable conditions for formation of dense aggregations resulted from the availability of clear-cut frontal zone caused by interaction of warm deep waters and the coastal waters. Such a confinement of fish aggregations to dynamically active zones arises rather from concentration of food organisms in these areas than as a result of favourable conditions for the fish.
The presence of cold intermediate layer shall be considered to be a negative hydrological factor for formation of icefish aggregations as it impedes descending food objects to the horizons inhabited by icefish and migration of fish to the upper 100m layer. Very high water temperature (above 1.8-2.0°C) for this area in the places of food organism aggregation is another obstacle for performing vertical migrations by foraging fish. All physiological processes of icefish begin to recede at such a temperature, and at a higher temperature the fish evidently falls into a condition close to anabiosis. In such locations the fish are distributed deeper than this temperature layer, most often near the ground.
As a rule, transition of icefish to pre-spawning condition is conditioned by visceral fat content (over 2 points). The spawning begins when near-bottom temperature on the spawning ground increases to 1.6°C. Therefore, the beginning of the spawning period is determined in the first place by oceanological factors.

In wintering period icefish do not form aggregations, is feeding inactively and disperse at the depths more than 250 m within rather narrow temperature range (1.6-1,7ºC). In this period the water temperature is a limiting factor restricting fish distribution.
In spring-summer icefish are feeding at the water temperature from 0.0ºC to 1.9ºC in the South Georgia area and to 2.0ºC near Shag Rocks. High level of energy exchange, intensive supply of food allow fish to distribute in the wider depths and temperature range. Taking in account the fact that in other habitats icefish occur at the water temperature below zero and never at the temperature higher than 2ºC, it is possible to assume that low water temperatures restrict fish distribution into the water waters.
Autumn includes the feeding and pre-spawning periods. Pre-spawning fish do not depend on the forage species distribution and migrate to the spawning grounds. These migrations occurred in the near-bottom layer. The impulse of the spawning migration beginning is the near-bottom water warming in the spawning ground up to 1.6º?. The amount of accumulated fat affects an individual fish readiness to spawning. Icefish spawning in the current year continue feeding, but the feeding activity decreases considerably and fish are gradually shifting to the wintering grounds.
Therefore, during the feeding period the abiotic conditions mainly affect indirectly icefish aggregations formation through the food items, distribution of which depends on hydrodynamic conditions, temperature, illumination, sea roughness, availability of phytoplankton aggregations, etc. During pre-spawning and spawning periods, icefish distribution and spawning beginning depend directly on the abiotic conditions, primarily with temperature. The same is true for the wintering period.

This paper presents an analysis of the distribution of albatrosses and petrels in the CCAMLR Convention Area (areas, sub-areas, divisions and sub-divisions), based on data from the Global Procellariiform Tracking Database. The results highlight the importance of the CCAMLR area, particularly for breeding distributions of populations of Wandering, Grey-headed, Light-mantled, Black-browed and Sooty Albatrosses, and populations of both Northern and Southern Giant-petrel and White-chinned petrel. The distribution data also emphasise the importance for breeding albatrosses and petrels of regions north of the CCAMLR boundaries. Overall, the CCAMLR sub-areas with the highest proportion of albatross and petrel distribution were Sub-Area 48.3 and 58.6, but the breeding ranges extend across the majority of the CCAMLR area, with the lowest proportion of distribution being in Sub-Areas 88.2 and 88.3. Current and future tracking studies will enable analysis of non-breeding albatross and petrel distribution, for which many data gaps currently remain.

In May and June of 2005 there was a trial of an Archipelago Marine Research video monitoring system within 58.5.2. The initial results from the monitoring of the hauling are optimistic but need to be fully analysed against the observer data that was generated for the same period. There is confidence that the trial achieved the objectives required of monitoring the hauling but the results of monitoring the setting operation were unsatisfactory due to operational and technical limitations of the system that was deployed.

Age Structured Production Model (ASPM) have been proposed and applied for Patagonian toothfish stock assessment at CCAMLR Subarea 48.3. Results obtained from this model, presented in the last meeting of WG-FSA-SAM held in Yokohama (Japan), show acceptable fit with standardized CPUE series, annual catches and observed catch length proportions (Wöhler et al., 2005 - WG-FSA-SAM 05/5).
In this paper, we applied the same model, but introducing a function modified from Brandão & Butterworth (2003) to estimate vulnerability patterns. Results were similar to those obtained in paper WG-FSA-SAM 05/5.

The comparative analysis of fishing and investigations on Antarctic toothfish distribution in the Ross Sea (Pacific Sector of Antarctic) show the complete failure of division of Subarea 88.1 on 12 SSRUs accepted in 2003 and allocation of TACs (quotas) based on the square areas of bottom and CPUEs (kg/1000 hooks) received for the other toothfish species (Patagonian toothfish) in Subarea 48.3 (Atlantic Sector of Antarctic).

Now after more then 30 years studies a most valuable commercial (target) species in the CCAMLR Area two species of genus Dissostichus. They have wide circumpolar distribution but difference in latitudes of the boundaries area distribution Patagonian and Antarctic toothfish . Our comparison Patagonian toothfish from Subarea 48.3 –Is. South Georgia and Antarctic toothfish from Subarea 88.1,88.2 – Ross sea show to us any similar features in the distribution and biology but some different characteristics these species in nominated regions.

This paper presents biological and fishery information available for skates from Division 58.5.2. Estimates of growth calculated from trawl-tagged, recaptured B. eatonii were 15 mm per year in total length and wing span, and 0.15kg per year in mass, indicating that this species is very slow growing. Composition of the skate bycatch by fishery and depth zone is described. Length-weight equations are provided relating total length and weight by species. The length at first maturity (L50) was estimated for B. irrasa at 865 mm and the length at first spawning (Lm50) at 1210 mm. Estimates of abundance of skates by species and stratum is presented from survey data. CPUE of skates by species from both research surveys and the commercial trawl and longline fisheries are also presented.

This paper describes aspects of the Management Strategy Evaluation (MSE) being developed to evaluate possible management strategies for the Patagonian toothfish fishery in Division 58.5.2. As requested by the Subgroup on Assessment Methods, we elaborate the plausible operating models currently being used for Patagonian toothfish in Division 58.5.2, the types of data and observations of the stock and the fishery being obtained from the region, the parameters that need to be estimated and the types of methods being used to assess yield of toothfish according to the CCAMLR decision rules. We summarise some preliminary results as well as the details of continuing work for assisting the special Subgroup on Assessment Methods workshop to be held prior to the meeting of WG-FSA in 2005. These results will be presented in an updated version of this paper provided to the workshop.