MONITORING CHANGES IN COASTAL FISH POPULATIONS BY THE ANALYSIS OF PELLETS OF THE ANTARCTIC SHAG Phalacrocorax bransfieldensis: A NEW PROPOSED STANDARD METHOD

CASAUX R.; BARRERA-ORO E.

Workshop; The CCAMLR Ecosystem Monitoring and Management Working Group; 1998

The Antarctic Shag Phalacrocorax bransfieldensis, previously known as the Blue-eyed Shag P. atriceps bransfieldensis, inhabits the Antarctic Peninsula and the South Shetland Islands. It usually forages solitarily diving to the bottom close inshore but occasionally exhibits a social feeding behaviour, of up to 200 birds diving synchronously (see Bernstein and Maxson, 1985; Casaux and Barrera-Oro, 1993a). The maximum dive depth and duration recorded for this shag is 112,6 m (Casaux et al., unpublished data) and 3,5 minutes (Bernstein and Maxson, 1985) respectively. This diving ability is similar to that reported for the South Georgia Shag (see Croxall et al., 1991; Wanless et al., 1992; Wanless and Harris, 1993) and is the deepest of all flying birds in Antarctica. During pre-laying and incubation partners forage once a day alternating the time at sea; females and males forage mainly during the morning and the evening respectively. During the chick rearing period, the parents increase the number of foraging trips as well as the foraging effort in order to match the increasing chicks? energetic demands (Bernstein and Maxson, 1984; Shaw, 1984; Favero et al., 1998 and Casaux, unpublished data).