CCAMLR

Long-lining operations for Dissostichus eleginoides off South Georgia were assessed for incidental mortality and interactions with seabirds. Twenty-seven lines were observed and ninety-eight mortalities recorded over twenty sets of the line; no mortalities occurred during hauls. The 16 sets made at night contributed 15% of the overall mortality, all of white-chinned petrels: the four day time sets contributed 85% of overall mortality, with giant petrels, grey-headed albatrosses and black-browed albatrosses predominating. Our data suggest that grey-headed albatrosses, whose populations at South Georgia are in serious decline, were disproportionately affected in relation to their numbers in the vicinity of the fishing vessel; giant petrels also may be disproportionately affected, at least in relation to the size of their breeding population at South Georgia when compared to the albatrosses. Average mortality rate for the twenty sets was 0.48 birds/1000 hooks and maximum mortality 3.12 birds/1000 hooks. Mortality and interactions of birds with operations varied with site and time of day, and due to behavioural interactions between birds. Setting only at night would dramatically reduce albatross deaths, but would substantially increase white-chinned petrel mortalities. A streamer line made to CCAMLR specifications may also reduce mortalities but may be less effective during calm weather, intense feeding activity by seabirds, or when incorrectly constructed.

A method of surveying incidental mortality of seabirds during longlining operations and the effectiveness of mitigation measures is described. An alternative design of streamer line for use with the 'Spanish' method of longlining (separate hauling and fishing lines) is described. The results of observations of incidental mortality of seabirds made during the fishing operations of the Korean longliner lhn Sung 66 are presented. Preliminary findings suggest that the phase of daylight during which the longline is set is more important than the use of a streamer line in the mitigation of incidental mortality. The use of a streamer line during setting of longlines during the day reduced the observed rate of bird deaths from snagging and drowning by 79%. More data are required to develop the investigation further.

This paper is a revision of the assessment of the competition between the Japanese krill (Euphausia superba) fishery and penguins (WG-Krill-93/7). Main fishing areas were confined to the slope and shelf to the north of either Livingston or Elephant Islands. In contrast, main foraging areas of penguins are considered to be formed in areas to the north of King George, Nelson and Robert Islands, and around Low, Clarence and Deception Islands. This little overlap between the main fishing and foraging areas is resulted from that large colonies of the dominant penguin (chinstrap penguins, Pygoscelis antarctica) are closely associated with areas where sea-ice disappears earlier in spring, not necessarily with areas of high krill abundance. The overlap between trawling depth and foraging dive depth of penguins was also insignificant. Furthermore, less similarity between krill caught by trawlers and those captured by penguins was observed. The above mentioned results imply a low level of competition between the fishery and penguins. Krill biomass was estimated to be as large as 200-1500 xl03 tonnes within the preferred fishing areas during the breeding season. Compared with the level of biomass (≥200 xl03 tonnes) and its variability (the order of 100 xl03 tonnes/half-month period), the present catch rate (≤13 xl0 3 tonnes/half-month period) is smaller by one or more orders of magnitude within the localized areas. Thus, the present fishery is very unlikely to have an adverse impact on the local krill biomass and hence on penguins,. when catch levels are also taken into account.

The consumption of food by the four species of breeding penguins at the Prince Edward Islands is assessed on an annual and seasonal basis. Total annual food consumption was estimated at 880 000 t, of which king penguins accounted for 74%, macaroni penguins 21%, rockhopper penguins 5% and gentoo penguins

Predator-prey interactions play an important role in determining the dynamics of pelagic ecosystems. Human intervention in such interactions can have effects that cascade throughout these ecosystems. Recently, concerns have arisen due to the commercial harvesting of Euphausia superba, the Antarctic krill, a keystone prey species in the Southern Ocean food web. It has been difficult to evaluate these concerns because of problems associated with determining the availability of krill to their natural predators. Here, we report a novel method for assessing prey availability to an important krill predator, Pygoscelis antarctica, the chinstrap penguin. Acoustic techniques were used to analyze the three-dimensional distribution of krill within a 1852 X 1852 X 100 m volume of ocean. Our study revealed the presence of at least six, distinct krill aggregations and substantial vertical and horizontal patchiness at scales of 10s to 100s of metres. Monte Carlo simulations revealed significant spatial concordance between the surface distribution of penguins and krill distributed in the 30 - 40 m depth layer; no spatial concordance was detected in shallower layers. We conclude that fine-scale, depth-dependent patterns of kill patchiness must be incorporated into analyses of krill availability to predator populations if we hope to predict predator responses to a changing food environment.