Feeding trial on an Imperial Cormorant Phalacrocorax atriceps: preliminary results on fish intake and otolith digeston

CASAUX R, M FAVERO, E BARRERA-ORO & P SILVA

Marine Ornithology

Año: 1995 vol. 23 p. 101 - 106

1018-3337

To assess the extent which the otoliths of different fish species may be differentially retained in pellets regurgitated by Imperial Cormorants or Blue-eyed Shags Phalacrocorax atriceps, a feeding experiment was carried out at Jubany Station, King George Island, South Shetland  Islands. For 45 days a captive cormorant was fed seven local fish species, regurgitated pelletscollected and otoliths counted and measured. A total of 16 pellets was produced. All fish species except Gobionotothen gibberifrons and Nototheniops nudifrons were under-represented numerically; no otoliths of Notothenia rossii were recovered. Losses in otolith size were substantial for most species but least for G. gibberifrons. These data provide preliminary factors for correcting estimates of number and mass of ingested fish, derived from otolith lengths.  During the feeding study the cormorant’s average daily consumption was 31% of body mass, a higher value than those recorded in studies of non-Antarctic cormorants. All remains of polychaetes in the pellets came from fish stomachs; previous studies may, therefore, have overestimated their importance in cormorant diets.Phalacrocorax atriceps, a feeding experiment was carried out at Jubany Station, King George Island, South Shetland  Islands. For 45 days a captive cormorant was fed seven local fish species, regurgitated pelletscollected and otoliths counted and measured. A total of 16 pellets was produced. All fish species except Gobionotothen gibberifrons and Nototheniops nudifrons were under-represented numerically; no otoliths of Notothenia rossii were recovered. Losses in otolith size were substantial for most species but least for G. gibberifrons. These data provide preliminary factors for correcting estimates of number and mass of ingested fish, derived from otolith lengths.  During the feeding study the cormorant’s average daily consumption was 31% of body mass, a higher value than those recorded in studies of non-Antarctic cormorants. All remains of polychaetes in the pellets came from fish stomachs; previous studies may, therefore, have overestimated their importance in cormorant diets.