Attendance of scavenging seabirds at trawler discards off Galicia, Spain

Abstract

The occurrence of scavenger seabirds at fishing trawlers was studied off Galicia, Spain. A total of 9,368 seabirds of 23 species were recorded during 92 fishing operations in 1998 and 1999. The most common species were the yellow-legged and lesser black-backed gull ( Larus cachinnans and L. fuscus ), Sabine´s gull ( L. sabini ), the northern gannet ( Morus bassanus ), the great shearwater ( Puffinus gravis ), sooty shearwater (P. griseus), the Manx and Balearic shearwater ( P. puffinus and P. mauretanicus ), the great skua ( Catharacta skua ) and terns (mainly Sterna hirundo and S. paradisaea ). Other species occurred in small numbers: Leach´s petrel ( Oceanodroma leucorhoa ), the storm petrel ( Hydrobates pelagicus ), the little shearwater ( Puffinus assimilis ), Cory´s shearwater ( Calonectris diomedea ), the parasitic skua ( Stercorarius parasiticus ), the pomarine skua ( S. pomarinus ), the black-headed gull ( Larus ridibundus ), the glaucous gull ( L. hyperboreus ), the kittiwake ( Rissa tridactyla ), the sandwich tern (Sterna sandvicensis), the black tern (Chlidonias niger), the guillemot ( Uria aalge ) and the little auk ( Alle alle ). The maximum number of seabirds recorded at a haul was 320. The maximum number of a particular species ranged from 120 great shearwaters to 250 yellow-legged/lesser black-backed gulls during a single haul. The differences in ship-follower species abundance are related to migratory movements but fisheries could also have a strong influence at a smaller scale on the distribution of seabirds off Galicia. The degree to which seabirds rely on fishery discards as food was not quantified, but may be important for several species.