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.