title: Sex-specific foraging behavior in response to fishing activities in a threatened seabird.
abstract: Some seabird species have learnt to efficiently exploit fishing discards from trawling activities. However, a discard ban has been proposed as necessary in Europe to ensure the sustainability of the seas. It is of crucial importance for the management and conservation purposes to study the potential consequences of a discard ban on the foraging ecology of threatened seabirds. We assessed the influence of fishing activities on the feeding habits of 22 male and 15 female Audouin's gulls (Larus audouinii) from the Ebro Delta (Mediterranean Sea) during the breeding period using GPS loggers together with Stable Isotope Analysis (SIA), which provided new insights into their foraging behavior and trophic ecology, respectively. GPS data revealed different sex-specific foraging patterns between workdays and weekends. Females were highly consistent in that they foraged at sea throughout the week even though discarding stops at weekends. In contrast, males switched from foraging at sea during the week (when discards are produced) to an increased use of rice field habitats at weekends (when fishermen do not work). This sex-specific foraging behavior could be related to specific nutritional requirements associated with previous egg production, an energetically demanding period for females. However, on a broader time scale integrated by the SIA, both sexes showed a high degree of individual specialization in their trophic ecology. The need to obtain detailed information on the dependence and response of seabirds to fishing activities is crucial in conservation sciences. In this regard, sex-specific foraging behavior in relation to fisheries has been overlooked, despite the ecological and conservation implications. For instance, this situation may lead to sex differentiation in bycatch mortality in longlines when trawlers do not operate. Moreover, any new fisheries policy will need to be implemented gradually to facilitate the adaptation of a specialized species to a discard ban scenario.
authors.affiliation: Departament de Biologia Animal, Facultat de Biologia, Universitat de Barcelona Av. Diagonal 643, 08028, Barcelona, Spain.
authors.forename: Manuel
authors.initials: M
authors.lastname: García-Tarrasón
authors.affiliation: Sociedad Española de Ornitología (SEO/BirdLife) C/Murcia 2-8 local 13, 08026, Barcelona, Spain.
authors.forename: Juan
authors.initials: J
authors.lastname: Bécares
authors.affiliation: Departament de Biologia Animal, Facultat de Biologia, Universitat de Barcelona Av. Diagonal 643, 08028, Barcelona, Spain ; Sociedad Española de Ornitología (SEO/BirdLife) C/Murcia 2-8 local 13, 08026, Barcelona, Spain.
authors.forename: Santiago
authors.initials: S
authors.lastname: Bateman
authors.affiliation: Sociedad Española de Ornitología (SEO/BirdLife) C/Murcia 2-8 local 13, 08026, Barcelona, Spain.
authors.forename: José Manuel
authors.initials: JM
authors.lastname: Arcos
authors.affiliation: Departament de Salut Pública, Facultat de Medicina, Universitat de Barcelona C/Casanova 143 5a planta, 08036, Barcelona, Spain ; Institut de Recerca de la Biodiversitat (IRBio), Universitat de Barcelona Av Diagonal 643, 08028, Barcelona, Spain.
authors.forename: Lluís
authors.initials: L
authors.lastname: Jover
authors.affiliation: Departament de Biologia Animal, Facultat de Biologia, Universitat de Barcelona Av. Diagonal 643, 08028, Barcelona, Spain ; Institut de Recerca de la Biodiversitat (IRBio), Universitat de Barcelona Av Diagonal 643, 08028, Barcelona, Spain.
authors.forename: Carolina
authors.initials: C
authors.lastname: Sanpera
keywords: Audouin's gull; ban on discards; common fisheries policy reform; foraging behavior; habitat use; seabirds; sexual segregation