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; Second World Seabird Conference; 2015

Fisheries areone of the main threats affecting the survival of most albatrosses and petrelsspecies around the globe.The fishing management (e.g. fishing quotas, prohibit fishing locations, etc.) couldhave a strong effect on several traits of seabirds? ecology such as theforaging behavior and the interactions with the vessels. There is an extensiveyear-round fishing closure in the Patagonian Shelf (area of approximately120,000 km2) where trawling is banned. The consequent concentrationof trawlers? fishing effort in the boundary of this area and strong overlappingwith the distribution of albatrosses triggered the question of a potentialexacerbated negative effect of bycatch in such border area. Hence,this study was conducted having as main objectives: (1) the analysis of theeffect of fishing closures on the flight patterns of Black-browed Albatrosses(BBAs) and Southern Giant Petrels (SGPs) as case study species known toextensively interact with trawlers, 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 tothe vicinity to fishing closure. For this, 55 satellitetransmitters were deployed on BBAs and SGPs between 1999 and 2013. Discrete behavioral mode (foragingvs. transiting) was inferred inside and outside the closure area from satellitemovement data using state-space models. Seabird bycatch datawere obtained from on-board observers. The spatial density for each behavioralmode and the seabird bycatch was determined by performing a Kernel density analysis rates. Foragingfor both species was concentrated on the border of the fishing closure where the fishing activity alsoconcentrated.  Contrarily, the presenceof the fishing closure did not influenced transiting behavior. Seabird-fisheryinteractions were significantly concentrated in the external boundary of the fishingclosure area (50% of the interactions in an area of about 70.000 km2)in comparison with other areas along the Patagonian Shelf. The studyhighlights that, although by definition seabird bycatch in closure areas isnil, in practice the ?exporting effect? due to the concentration of bothfishing effort and seabird foraging in border areas may substantially increaseseabird by-catch in the immediate neighboring waters. Hence, the design ofconservation management measures for seabird by-catch should contemplatespecific regulations to address these negative side effects of concentratingboth fishing and seabird activity in border areas.