Utilization of discards from artisanal fisheries by seabirds on the Parana coast of Brazil

The present study was conducted on the coast of Paraná, southern Brazil over two years. We evaluated interactions between birds and artisanal fishery discards on the shore line and on the open sea. We counted 20 species of birds, of which nine consumed discards on the shore line, Larus dominicanus was the most frequent species. The three study areas had similar numbers of scavenging species, but larger numbers of birds congregated where amounts of discards were highest. We observed eight species of scavenging seabirds taking discards on the open sea, Fregata magnificens and Sula leucogaster were the most abundant and frequent species. Kleptoparasitism was observed in 57 times, with a prevalence of intraspecific interactions (72%), mostly involving Sula leucogaster (63%). Trawl fisheries provided far more discards at sea and shore line than driftnet fisheries, and numbers of scavenging seabirds were higher at boats using trawl nets. During a fishing moratorium, when no use of trawl nets was permitted, less discards were made available to birds and numbers of scavenging seabirds at boats were lower, but kleptoparasitism was more frequent, indicating that there were high levels of competition. It seems likely that scavenging seabird populations off the Paraná Coast benefit from this supplementary food supply, but the extent to which their numbers are affected is not yet known.