New correction factors for the quantification of fish represented in pellets of the Imperial Cormorant Phalacrocorax atriceps.

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

MARINE ORNITHOLOGY

Año: 1998 vol. 27 p. 54 - 59

1018-3337

A comparative analysis was carried out on stomach contents and pellets (regurgitated casts) of the Imperial Cormorant Phalacrocorax atriceps collected throughout the breeding season at Nelson Island, South Shetland Islands, Antarctica. This allowed an estimation of correction factors to compensate for the loss and digestion of otoliths in pellets and more accurately estimate the real mass of ingested fish. These factors were calculated for Notothenia coriiceps, Harpagifer antarcticus, Nototheniops nudifrons, Trematomus newnesi, Gobionotothen gibberifrons, Notothenia rossii, Pagothenia bernacchii and Parachaenichthys charcoti, but not for Pleuragramma antarcticum, Notolepis coatsi and Electrona antarctica since they  were only represented in pellets. Fish were the main prey and N. coriiceps and H. antarcticus were the dominant species both in mass and number. Observations of activity patterns showed that daily foraging trips per bird increased in number but diminished in duration through the breeding season. These trends reflected the increase in the chicks’ energetic demands.Phalacrocorax atriceps collected throughout the breeding season at Nelson Island, South Shetland Islands, Antarctica. This allowed an estimation of correction factors to compensate for the loss and digestion of otoliths in pellets and more accurately estimate the real mass of ingested fish. These factors were calculated for Notothenia coriiceps, Harpagifer antarcticus, Nototheniops nudifrons, Trematomus newnesi, Gobionotothen gibberifrons, Notothenia rossii, Pagothenia bernacchii and Parachaenichthys charcoti, but not for Pleuragramma antarcticum, Notolepis coatsi and Electrona antarctica since they  were only represented in pellets. Fish were the main prey and N. coriiceps and H. antarcticus were the dominant species both in mass and number. Observations of activity patterns showed that daily foraging trips per bird increased in number but diminished in duration through the breeding season. These trends reflected the increase in the chicks’ energetic demands.