Exporting seabird by-catch: concentration of seabird foraging activity and fisheries interactions around closure areas

COPELLO S.; BLANCO, G.; SECO PON, J. P.; QUINTANA, F.; FAVERO, M.

Conferencia; II World Seabird Conference; 2015

Fisheries are one of the main threats affecting the survival of seabirds around the globe. Fisheries management (e.g. fishing quotas, closures) may impact on a range of seabirds? traits such as foraging behavior. There is an extensive fishing closure in the Patagonian Shelf (120,000 km2) where trawling is banned. The concentration of fishing effort in the boundary of this area and the strong overlapping with the distribution of seabirds triggered the question of a potential exacerbated negative effect of bycatch in such border area. Hence, this study was conducted having as main objectives: (1) the analysis of the effect of fishing closures on the flight patterns of Black-browed Albatrosses and Southern Giant Petrels, and (2) the analysis in space and time of seabird-fisheries interactions (i.e. contacts with the fishing gear as a proxy of risk of mortality) in relation to the fishing closure. For this, 55 satellite transmitters were deployed on the birds between 1999 and 2013. Discrete behavioral mode (foraging vs. transiting) was inferred from satellite transmitters using state-space models. Seabird bycatch data were obtained from on-board observers. The spatial density for each behavioral mode and the bycatch was determined by performing a Kernel analysis. Foraging in both species was mainly concentrated on the border of the fishing closure. However, the fishing closure did not influence transiting behavior. Seabird-fishery interactions were concentrated in the external boundary of the fishing closure (50% of the interactions in 70.000 km2) in relation with other areas distant to the closure. The study highlights that, although seabird bycatch inside closure areas is null, the ?exporting effect? due to the concentration of fishing effort and seabird foraging in border areas may increase seabird by-catch in the neighboring waters. Hence, the design of management measures for seabird by-catch should contemplate regulations to address these negative side effects.