Interactions of long-line fishing with seabirds in the southwestern Atlantic Ocean, with a focus on White-capped Albatrosses (Thalassarche steadi)

Abstract

We analyse the interactions of seabirds with the Uruguayan long-line fishing fleet in the south-western Atlantic Ocean, with a focus on White-capped Albatrosses (Thalassarche (cauta) steadi). The aim of this work is to determine the species composition of the incidental by-catch of seabirds and assess the importance (in terms of abundance) of White-capped Albatross in the seabird assemblage attending this fishery. Counts of seabirds associated with fishing vessels (n =132 counts) were made during five commercial fishing trips in Uruguayan waters, and the incidental by-catch of seabirds per line-set (n = 44 line-sets) was recorded. Of 25 species of seabird recorded in association with the vessels, five were incidentally caught on long-lines. The relative frequency of occurrence of shy-type albatrosses (cauta-type) observed was 25% and their abundance was in the range 0–20 birds; most birds seen were immatures. The three specimens of shy-type albatrosses caught, along with two other specimens caught by the fleet in 2004, were identified by molecular analysis. All were confirmed to be White-capped Albatrosses, suggesting this species is the predominant one among the shy-type albatrosses occurring in the region. Before this study, there was little information on seabirds for this region of the south-western Atlantic Ocean and it was not included in the distribution of the White-capped Albatross. However, the results of this study confirm its occurrence in this region, expanding its global range and show that it is exposed to pelagic long-line fisheries in this part of the Atlantic.