The role of Southern Giant Petrel as a ship-follower in the Patagonian Shelf

SOFÍA COPELLO; FLAVIO QUINTANA; DIEGO GONZÁLEZ ZEVALLOS; HUGO BRACHETTA; GUILLERMO CAILLE

Montevideo, Uruguay

Congreso; Third International Albatross and Petrel Conference, IAPC; 2004

Several species of scavenging seabirds follow vessels; this birds are attracted by discards and offal made available by fishing fleets. Consequently, the fishing operations turn out the incidental capture of seabirds in nets or hooks. Ocurrence and bycatch of the Southern Giant Petrel (Macronectes giganteus, SGP) were determined on three Patagonian fisheries (hake trawlers (HT), Jiggers (J) and Southern blue whiting trawlers (BWT)) between 42º and 55º S at the Patagonian shelf. At-sea positions of satellite-tracked adult breeders were also used to visualize the spatial overlap between the commercial fisheries and the areas used by the birds. During the breeding season, there was a spatio-temporal overlap between the fishery distributions and the areas used by females SGP. The SGP were observed following vessels during the different activities recorded in the three fisheries (sailing, towing, haulback and anchored). Occurrence was always higher than 50% (except for one activity of the Jiggers) and the highest occurrences were observed in BWT (87-100%). However, the relative abundance of SGP (number of SGP/total number of birds) was low (range 0.5-48%). Occurrence was always higher (>70%) during discards operations for all the vessel activities. The average number of SGP following ships was different between activities for the three fleets and in all the cases, the abundance of SGP increased during discards operations. We not recorded SGP incidental mortality in none of the fleets. Our study suggest that, in the Patagonian shelf, the SGP is not harmed by incidental mortality in the studied fisheries and might have benefits through the provision of discards and offal.