Seabird assemblages attending longline vessels in the Argentinean Economic Exclusive Zone

PATRICIA A. GANDINI; JUAN P. SECO PON

ORNITOLOGIA NEOTROPICAL

NEOTROPICAL ORNITHOLOGICAL SOC

Año: 2007 vol. 18 p. 553 - 561

1075-4377

The aim of this work was to study the specific composition and relative abundance of seabirds attending commercial longline vessels operating in the Argentinean Exclusive Economic Zone (AEEZ). Daylight counts were performed on board of semi-pelagic and bottom longline cruises during 2003, 2005 and 2006. We registered an overall of 56.510 birds comprised by at least 21 different species belonging to eight families. The Procellariiforms, with 17 species, were the most abundant bird taxa. During this study, the greatest species diversity took place in the spring months (15 taxa), while in autumn and summer the diversity was intermediate (13 and 7-10 taxa respectively). In spring 2003, the commonest species attending the vessels was the Cape petrel (Daption capense) while in autumn, adult Black-browed Albatrosses (Thalassarche melanophris) were the most common species. Again, adult Black-browed Albatrosses were the most abundant birds attending the vessels during spring and summer of 2005. Finally, the Great Shearwater (Puffinus gravis) was the commonest species during summer 2006. More than 75% of the species registered are migratory and non-breeders in Argentina. During the austral winter, several seabird species from Antarctica and sub-Antarctic Islands moved north, reaching the waters of the AEEZ. This northward dispersion is performed chiefly by Procellariiforms breeding in those regions. The combination of the rich year-round foraging grounds provided by the waters of the south-western Atlantic Ocean, particularly the AEEZ and the great seabird and other top predator biomass, highlights the global ecological importance of this region.