CCAMLR

Satellite telemetry was used to identify the foraging zones of Shy Albatrosses Diomedca cauta breeding at two sites of Tasmania, Australia (Albatross Island in western Bass Strait and Pedra Branca to the south) to assess their level of interaction with longline fisheries. Adult birds from both colonies fed locally both in and outside the breeding season. Breeding birds from Albatross Island foraged over the Australian continental shelf or slope waters off northwest Tasmania, while those from Pedra Branca foraged between the colony and the southeastern edge of the continental shelf. The distances travelled by the birds and the duration of their foraging trips varied during the breeding cycle and tended to decrease as eggs approached hatching Adults which were tracked near the end of the breeding season (March-April, n = 7 birds) deserted their chicks prematurely, and while dispersing further than incubating or brooding birds, they rcmained over the continental shelf and slope waters off southeast Australia. Home range analyses indicatcd 41%, overlap between foraging zones of birds during successive breeding stages. Dispersal during the postbreeding period extended the foraging zones with less overlap between individuals (10% for Albatross Island and 19% for Pedra Branca). The recent contraction of the Japanese Southern Bluefin Tuna longline fishery to the south and east coasts of Tasmania has resulted in extensive overlap with adult Shy Albatrosses from Pedra Branca, but appears to pose a minimal threat to adult birds from Albatross Island. Coupled with the concomitant increase In the Australian domestic tuna longlining Industry, adult Shy Albatrosses from southern Tasmania (Pedra Branca and the Mewstone) are vulnerable to incidental capture throughout their annual cycle.

Longline fishing for Patagonian toothfish Dissostichus eleginoides commenced at the Prince Edward Islands in October 1996, but unsanctioned fishing commenced some months before this date. This paper summarizes the mortality of seabirds associated with this fishery during the year July 1996-June 1997. Data on seabird bycatches were obtained from fishery observers aboard 10 of 12 sanctioned fishing trips. Some 3.2 million hooks were observed during the period November-June, representing 84 % of the estimated 3.8 million hooks set by permit-holders in the South African Exclusive Economic Zone (EEZ). However, the total fishing effort is estimated, based on landings, to be between 20 and 50 million hooks.
Average bird bycatch rate was 0.289 birds per 1000 hooks set. However, there was considerable variance between vessels (range 0.004 to 1.468 birds per 1000 hooks) as a function of fishing season, time of setting, distance from the Prince Edward Islands, mitigation measures employed, and type of fishing gear used. Observers reported 923 birds of 10 species killed. The species most affected were White-chinned Petrels Procellaria aequinoctialis (73 % of the total killed), Grey-headed Thalassarche chyrsostoma and Yellow-nosed Albatrosses T. chlororhynchos (together 23 %), and giant petrels Macronectes spp. (4 %). Extrapolating to the total fishery suggests that between 5 000 and 20 000 birds were killed during 1996-97. This excludes birds killed that were not hauled aboard vessels. Ten toothfish hooks were found in birds or in bird pellets on Marion Island during 1996-97. Almost all birds killed were breeding adults, and there was a significant bias towards males in at least three species. More than 1 % of four or five local breeding seabird populations were killed during the 1996-97 season. Given the low reproductive rate of these species, these levels of mortality (exacerbated by mortality in other longline fisheries) are not sustainable, and will result in local population declines.
Bird mortality can be largely avoided by setting lines only at night, using a CCAMLR-approved bird-scaring (tori) line during setting, and not fishing during the main summer breeding season (or at least fishing >200 km from the breeding islands during this period). These measures were largely disregarded during most of the 1996-97 season. Unfortunately, the necessity for a presence around the islands to reduce the impact of uncontrolled fishing renders the last option impractical in the short term. It is important that observers continue to be placed aboard all vessels to monitor catches of both fish and birds, and to ensure compliance with regulations to reduce bird bycatch.

This work aims to the study of the distribution, size structure by depth, first maturity stage, weight/length, and length perimeter curve, of Patagonian toothfish (Dissostichus eleginoides) in the Argentine Sea, and atempts some explanation by a trophic analysis of such distribution.
The distribution of Patagonian toothfish extends between of 36°30'S and 55°S from 80 to 2500 m depth. Greatest concentration areas were found south and NE of the Malvinas Islands, over the slope of Buenos Aires province and between Burdwood Bank and State Island, this last place being where the studies were carried on. Bottom temperatures ranged between 2°C and 12°C. Extreme sizes were between 12 and 227 cm, and most of the adult sizes (>80cm) were found in waters at depths greater than 900 meters. The selectivity perimeter should be bigger than 46 cm. The new maturity curve range at 50% 78,27 for males, 87.06 for females and both 82,16. The length/weight curve for males was: a=5E-06; b=3.186; females: a=5E-06; b=3.161; both: a=4E-06; b=3.187.
The distribution of adults and juveniles can be explained partially by canibalism and the size of the available preys at different depth. According to the analysed data in different areas including CCAMLR area, longline or trawl operation fishing is recommended starting from 900 meters depths, in the southern area, South of 54°S and 1000 m in 38°S to 48°S and to assume a conservative position of 1000m for all the area.

The diet composition of mackerel icefish Champsocephalus gunnari caught in Subarea 48.3 in late summer of years 1994-97 was analysed using frequency of occurrence (F%) and coefficient "Q" (%) methods. Krill (Euphausia superba) followed by the amphipod hyperiid Themisto gaudichaudii was the main food item around South Georgia and Shag Rocks in the period investigated, except in 1994, when the order of importance of these two organisms in the diet was inverted. The consumption of other prey items such as mysids and Thysanoessa sp., which are known as important alternative food in years of krill scarcity and fish, was only occasional or in negligible amounts, showing interannual variation. The spatial distribution of the main preys in the diet as well as of the proportions of stomachs with/without food in the area of investigation didn't show a consistent pattern from year to year. Likewise, in the four Holmberg 1944-1997 surveys, high proportions of fish exhibited empty stomachs, phenomenon for which non consistent explanation was found. The variation of the diet with respect to the length of C. gunnari didn't show a selectivity pattern for any of the prey items. The availability of krill in the Statistical Subarea 48.3 in the period investigated can be defined as low in 1944, equivalent to those years of krill scarcity; intermediate in 1995, below the historical years of high abundance; and high in 1946 and 1997, in line with the years of krill richness. This information is well in accord with independent information from acoustic surveys and krill dependent species monitored in the CEMP.

The survey comprised 51 bottom trawl hauls taken in subarea 48.3. Of these, one was discarded due to net damage. About 80% of the hauls were taken in the shelf of South Georgia Islands (41) and the remaining in the Shag Rocks area (9); 64% of the hauls were intended as replicates of the position of hauls in the previous cruises. Mean densities were obtained considering the spatial aggregation of stations in a nested ANOVA model. No significant changes in the mean densities of several species, including Champsocephalus gunnari at the shelf of the South Georgia Islands. The age and size structure of this species in the whole subarea 48.3, is dominated by younger fish (less than two years). Four years and below: 99.07% at the South Georgia Islands and 98.57 % at Shag Rocks.

The results of four fish surveys (EDUARDO L HOLMBERG 1994 to 1997) are analyzed to detect associations between the sizes of Champsocephalus gunnari (also age classes) , Gobionotothen gibberifrons, Notothenia rossii, Pseudochaeinichthys georgianus, Chaenocephalus aceratus and Dissostichus eleginoides and depth of catch, as well as among C. gunnari age classes. Except D. eleginoides median sizes of all species resulted significantly associated with depth, positively in the case of C. gunnari and N. rossii and negatively for the remaining species. Less association with depth is observed in C. gunnari as the fish grow older, indicating that the spatial separation is controlled by depth. The accumulated catches of age I- present maximum difference with the older age classes at about 150 meters a result which might be used to fish different age fractions of the populations, thus regulating the age composition of the catches.