MEPS 484:279-286 (2013)  -  DOI: https://doi.org/10.3354/meps10312

ABSTRACT: The effect of fisheries on seabirds is a key issue for seabird conservation and management. Fish discards, for instance, are an important and significant food resource for many bird species. Despite extensive research, the attractiveness of fishing fleets to seabirds has not been fully explored. We compare the densities of the near-threatened Audouin’s gull Larus audouinii in 2 areas off the Ebro delta (NW Mediterranean) which are affected by 2 trawling moratoria in different months of the breeding season (May–June and July–August, respectively). We assessed and quantified the effect of fisheries and moratoria on the species’ density in both areas under both fishing scenarios by monthly aerial surveys. The gull’s distribution is strongly influenced by the trawling moratoria as it overlaps with that of the operating trawlers. Audouin’s gulls are scarcer in areas where trawling is prohibited. A complementary analysis of the presence of color-ringed L. audouinii at Tarragona and Borriana harbours (located 75 km north and 100 km south of the delta, respectively) showed similar results, with a decrease in the number of individuals during the span of the moratoria. Our findings highlight the strong influence of fisheries on the distribution of L. audouinii. The strong dependence of L. audouinii on discards from the fishing fleet suggests that the management and conservation of this species must be directly linked to fishery management by the respective stakeholders. This will help ensure the long-term sustainability of L. audouinii colonies in this marine important bird area.

KEY WORDS: Seabird · Distribution · Larus audouinii · Ecology · Trawling · Fishery moratorium · Ebro delta · Mediterranean Sea