CCAMLR

Shipboard tracking study of breeding chinstrap penguins (Pygoscelis antarctica) and Antarctic fur seals (Arctocephalus gazella ) at Seal Island were conducted to identify and evaluate their foraging areas in late December 1994 (Leg I) and late January 1995 (Leg II). Leg I and Leg II corresponded to the incubation and guard period, respectively, for chinstrap penguins ; penguins were divided into diurnal and overnight foragers during Leg II. Highest krill (Euphausia superba) densities regularly occurred on the shelf north of Seal Island. However, all predators except diurnal foraging penguins went northward beyond the shelf, and foraged in offshore region during Leg I and on slope during Leg II. The diurnal foraging penguins alone fed on the shelf. The following advantages are considered for feeding in the offshore/slope regions over on the shelf: (1) krill were present near the surface throughout the day so that only shallow diving was required to catch krill even in the day time; (2) krill tend to be larger in size; and (3) Myctophid fish occurred within the predators' maximum diving range at night. Considering that overnight foraging was always made in the offshore/slope regions, (3) is regarded as the most important factor making the predators except diurnal foragers choose the offshore/slope regions (less abundant areas for krill) over the shelf region (more abundant areas for krill).

The diet of Cape petrel was investigated on Mossman Hills, Laurie Island, South Orkney Islands in January-February 1995. Twenty stomach contents were sampled by a water offloading method, during late incubation and chick-rearing period. The analysis of the samples showed that Euphausiids were by far the main prey. Antarctic krill Euphausia superba constituted the bulk of the diet, predominated in mass (97.2%) and in frequency (95% ). Our results reflect broad similitary with other studies conducted during the same period of the life cycle.

A proposal to monitor changes in coastal fish populations is presented in this document. The methodology considered is based in the analysis of regurgitated pellets of the blue-eyed shag Phalacrocorax atriceps. The fundaments of the proposal as well as the methods tested and the steps followed are also provided.

A comparative analysis was carried out on stomach contents and pellets (=regurgitated cast) of the blue-eyed shag or imperial cormorant Phalacrocorax atriceps collected throughout the breeding season at Nelson Island, South Shetland Islands. This allowed to estimate correction factors necessary for the quantification of fish represented in pellets. These factors were obtained for Notothenia coriiceps, Harpagifer antarcticus, Nototheniops nudifrons, Trematomus newnesi, Gobionotothen gibberifrons, Notothenia rossii, Pagothenia bernacchii and Parachaenichthys charcoti whereas Pleuragramma antarcticum, Notolepis coatsi and Electrona antarctica were represented in pellets but not found in the stomach contents. Fish were the main prey and N. coriiceps and H. antarcticus were the dominant species both in mass and number. Observations on behaviour showed that the daily foraging trips per bird increased in number but diminished in duration throughout the breeding season. These trends are related to the increase in the chicks' energetic demands.

One hundred and thirty nine stomach contents of the blue-eyed shag Phalacrocorax atriceps were sampled at Nelson Island, Antarctica, between 1 December 1994 and 2 February 1995. Fish were by far the main prey, followed by octopods, gammarids, euphausiids and polychaetes. Notothenia coriiceps, predominated in frequency (56%) and in mass (55%), whereas Harpagifer antarcticus was the most important by number (60%). The mean mass of the stomach contents was 220 g, whereas the mean number of fish was 7.4 (range 1-34). Eight hundred and sixty four bird h-1 of observations on 5-7 nests showed that the adults averaged 1.7 trips day-1 during incubation, 2.0 trips day-1 in early rearing and 4.6 trips day-1 during late rearing period. The estimated daily intakes reached 352, 462 and 1017 g respectively.

The analysis of twenty nine stomach contents collected in a colony close to Pirie Peninsula, South Orkney Islands, from 2 January to 18 February 1995, showed that fish were by far the main prey of the blue-eyed shag Phalacrocorax atriceps, followed by octopods, decapods and gammarids. Notothenia coriiceps constituted the bulk of the diet; however, its importance decreased by the end of the study when Nototheniops nudifrons was the most important prey. The composition of the diet varied throughout the breeding season according to changes in the chicks' energetic demands. The results are compared to those obtained previously in the area and the possibility that the stomach contents primarily represents the chicks diet is discussed.

Detection of climate-induced change in marine ecosystems requires a knowledge of the underlying variability of the environment. This paper uses a range of datasets to investigate the interannual variability in Southern Ocean sea-ice dynamics. We present the first analysis of a series of fast-ice duration data from Signy Island, which we have cross-calibrated and combined with an earlier series from the same island group. The combined series covers the period from 1903 to the present day. The analyses indicate that there has been a long term decline in the duration of sea-ice at the South Orkney Islands in the north-west Weddell Sea. This change has not been a simple linear decline but appears to have been the result of a reduction in the duration of fast-ice during the 19405 and 1950s. There was a pronounced sub-decadal cycle in fast-ice duration at the South Orkney Islands from the mid-1960s to 1990. In recent years this cyclicity has broken down and fast-ice duration has been greater than expected. Analyses of satellite data have shown that fast-ice duration at Signy Island reflects the larger-scale ice dynamics of the Wed dell Sea. Investigation of the Weddell Sea ice dynamics in relation to circumpolar ice extents indicates that the position of anomalies in the maximum sea-ice extent field precesses around the Antarctic continent with a period of approximately 7-9 years. Analysis of atmospheric and oceanic connections with the sea ice variability show that there are signals in both regimes. 1bis environmental variability has significant implications for ecosystem function and the detection of short-term and long-term ecological change.

A total of 45 pellets from the blue-eyed shag Phalacrocorax atriceps were collected in January 1994 at Duthoit Point, Nelson Island, South Shetland Islands. The analysis showed fish as the main prey, followed by octopods, polychaetes and gastropods. Notothenia coriiceps formed the bulk of the diet, but Harpagijer antarcticus was the most frequent and important fish in number. The prey represented in the pellets were consistent with those observed in stomach contents sampled simultaneously in the same colony; however, they differed in importance. A daily mean of 0.7 pellets per bird was collected, representing 255 g of fish. Correction factors previously estimated in a feeding trial were applied to this value, and suggested that the average daily amount of food ingested by an adult shag during the sampling period was 1325 g, which fall into the range observed by the analysis of stomach contents. Other aspects related to the feeding behavior of this bird are also discussed.

One hundred and seventy three regurgitated casts of the blue-eyed shag or imperial cormorant Phalacrocorax atriceps were collected in a colony at Half-moon Island, South Shetland Islands, by weekly sampling throughout the breeding season from December 1993 to February 1994. Demersal-benthic fish were the main prey (91% in number) followed by mollusks and polychaetes. Six fish species were represented: Notothenia coriiceps, Nototheniops nudifrons, Trematomus newnesi, Harpagifer antarcticus, Gobionotothen gibberifrons and Pagothenia bernacchii. Notothenia coriiceps was the most frequent (F%=73) and important in mass (79%), followed by N. nudifrons and T. newnesi. The overall composition of the diet was qualitatively and quantitatively similar to that reported for the 1992/93 austral summer at the same colony. However, the pellet analysis throughout the 1993/94 breeding season showed that large N. coriiceps were the main prey during the chick rearing period, whereas when chicks were fledging/post- fledging the diet was more diverse and comprised chiefly prey of lower energetic content like other smaller fish species and non- fish organisms. This may reflect different degrees of energy demand by chicks at different stages of the season.