CCAMLR

To examine consistency among laboratories in age estimation of Patagonian toothfish and the effects on readings of different otolith processing methods, scales and otoliths were taken from 124 fishes caughts in Argentine Sea ( South West Atlantic)
Ages were estimated by readers from National Institute for Fisheries Research and Development (INIDEP) Argentine, National Institute of Water and Atmospheric Research, Nelson, New Zealand (NIWA), and Centre for Quantitative Fisheries Ecology, Old Dominion University, Norfolk, Virginia, United States of America. (CQFE).
As a consequence of the exchange of otoliths carried out with NIWA, and the results presented, it is apparent that the NIWA preparation method produced a clearer section. More hyaline bands were visible in the NIWA preparations, particularly near the otolith margin where the zones can be very narrow. Consequently, INIDEP has adopted the NIWA method to process otoliths of the Patagonian toothfish from the Argentine Sea.
So even though Patagonian toothfish otoliths could not be classified as easy to read, the clarity of their zones is quite similar in the South Atlantic, the waters south of New Zealand, and CCAMLR subarea 48.3.
The comparisons of age data produced by three readers indicate a reasonable consistency for otoliths. The indices of average percent error for comparisons between R1 and R2 are satisfactory. Reader R3 generally produced older age because he has a different interpretation of the first few increments.
Comparisons of age estimations derived from scales and otoliths are less consistent.There were significant differences in age determinations from scales between R1 and R3, and between scales and otoliths by R1 and R3. Clearly, there are differences between these readers in the interpretation of these structures, and also difficulties reconciling the counts derived from otoliths and scales from individual fish. Further work is necessary on this issue to develop consistent interpretations for age readings.

The diet of the mackerel icefish was investigated from stomach contents analysis of fish caught in research trawls at South Georgia and Shag Rocks in January 2004. The results are consistent with previous studies, with the dominant species consumed being Antarctic krill (Euphausia superba), the pelagic amphipod (Themisto gaudichaudi) and mysids. The diet differed between the age classes of icefish examined (2+, 3+ and 4++), with the younger fish consuming more T. gaudichaudi and small euphausids and the older fish taking more krill and fish. The change in diet reflects a shift from smaller to larger prey items with size.

The diet of juvenile (

Twenty-eight species of seabird were reported from observations during longline setting operations that targeted toothfish (Dissostichus spp.) in 2001–03 in Sub-areas 88.1 and 88.2. The distribution of fishing effort was dictated by the presence of sea ice and there are differences in the seabird composition reported each year because of variation in the spatial distribution of the seabirds. At-sea identification of some species is difficult and some of the species that were reported from outside their known distribution range may have been misidentified. The most commonly seen seabirds were cape petrels (Daption capense), Antarctic petrels (Thalassoica antarctica), Wilson's storm petrels (Oceanities oceanicus), and snow petrels (Pagodroma nivea). The highest species diversity was in waters north of about 70º S off the continental shelf. Seabirds were not always seen in attendance at the setting operation and appeared to be generally uninterested in the line setting and were more likely to be well astern of the vessel. There were very few observations of seabirds diving on the bait during the set. Lost bait or bycatch fish species, mainly rattails (Macrourus spp.), were taken by some seabird species during hauling, but this feeding was away from the vessel activity. Nine marine mammal species were observed close to vessels during hauling, but there were few observations.

The interaction of icefish and krill in the South Georgia area has been analysed on the basis of the trawling, acoustic and juvenile fish surveys carried out by AtlantNIRO during 1986-2002 and the data of the national fishery. It is demonstrated that ?.gunnari both at the early development stages and as adults utilize the pelagic forage resource, the bulk of which is constituted by krill. At the same time krill content in the food of different length groups varied. The effect of krill on icefish growth and spatial distribution at various development stages is discussed. It is shown that near-bottom-pelagic distribution pattern of fish is sufficiently stipulated by the impact of krill distribution, being the preferred food item, on icefish diurnal vertical migrations. The comparison analysis of spatial distribution of near-bottom and pelagic fish aggregations density relative to krill distribution is presented.

The living conditions of Champsocephalus gunnari in the eastern, western shelf areas of South Georgia and at Shag Rocks are different. The length-age structure of C.gunnari groupings inhabiting the areas at Shag Rocks and South Georgia is characterized with the lack of fish below 11 cm in length and older than 6-7 years (10-11 years in the South Georgia area) and considerably lower number of large fish above 40 cm in length in catches. These distinctions are the result of a certain geographic isolation of the area. On the basis of the cluster analysis the similarity of icefish up to 22 cm in length has been revealed in the western and Shag Rocks groupings and differences between those and the eastern grouping both in otolith morphology and morphometric characteristics. In larger fish the similarity between the eastern and western groupings and the differences between those two and Shag Rocks grouping appears. These differences increase with fish length. The analysis of all data available allows to assume the common origin of the western and Shag Rock groupings. C.gunnari of two-three years old (at the length of 22-23 cm) migrate from the South Georgia area and remain at Shag Rocks. Icefish reaching 40-43 cm in length either die or return to the Island. The results obtained provide the basis to assume with a high probability that C.gunnari population in the South Georgia area is the major reproductive unit of the area distributing currently near the Island, while the shallow Shag Rocks area is a zone of the life space extension or the feeding zone.

Records of seabirds collected by on board observers on different research or fishing vessels between the years 1994 and 2003 are presented. A total of 883 daily census were included. 22 species and three genera were identified in the Atlantic Ocean, within an area between 20ºS and 57ºW and from the Uruguayan coast up to 30ºW of longitude. This preliminar paper refers to cualitative data (presence-absence), the description of the area, the species and records constraints.

Between August and November 2001, two fishing vessels carried out exploratory and experimental surveys with semipelagic and different configurations of long line directed to the capture of Wreckfish (Polyprion americanus) and other fish species within the Uruguayan EEZ. Observers were trained in order to include Seabirds information along with their common tasks. Seabirds mortality associated with long line operation is analyzed, as well as species involved and mitigation measures application. Total mortality ranged: 3 birds/1 000 hooks, and main species captured were Procellaria aequinoctialis (50%), Puffinus gravis (27%) y Thalassarche melanophrys (21%). Bird species composition varied along the operation period. No significant differences in mortality were found between long line types, being higher in those with floats attached to the main line, and under daylight setting. Some species presence was consistent comparing their abundance during line setting and resulting mortality. Difficulties were found in mitigation measures application, specially to set during night only and avoiding bird scaring tangles with intermediate buoys. Although this fishery is no longer in Uruguay, the need to improve some information related to fishing gear and seabirds interaction is discussed, as well as the revision of current regulations.

The ASPM assessment of the Prince Edward Islands toothfish resource by Brandão and Butterworth (2004) that permitted annual fluctuations about a deterministic stock-recruitment relationship is updated to take account of further catch, GLM standardised CPUE and catch- at-length information that have become available for the year 2004. Twenty year biomass projections under the assumption of various constant annual catches are also shown. These suggest that maintenance of the present TAC of 500 tonnes is defensible.