Spatial overlap and effect of fishing effort on the foraging behavior of the Great Shearwater (Ardenna gravis) on the Argentine Continental Shelf

PAZ, J.; RONCONI, R.; COPELLO, S.; SECO PON, J. P.; RYAN P.; FAVERO, M.

Conferencia; 3rd World Seabird Conference; 2021

Large numbers of Great Shearwaters (GSH, Ardenna gravis forage over the ACS. This species interacts with ice-chilling andfreezer trawlers that target hake Merlucciushubbsi and has high rates of bycatch incoastal pelagic trawlers targeting anchovy  Engraulis anchoita. This study analyzes theoverlap between the distributions of adult (2009-2010 period) andimmature (2006, 2008-2010 periods) GSHs and a range of fishing fleets, as well as assessing the effect of fishing effort onshearwater foraging behavior. The database comprised fisheries effortfor 9 fleets, and 21 GSH tracked by satellite telemetry. The trackingdata were analyzed with switching state-space models (SSSM) to inferbehavior (transitory or foraging) at each location. The overlap wasanalyzed using the UDOI index (no overlapping = 0, complete overlapUDOI ≥ 1), while the effect of fisheries on foraging behavior wasanalyzed using GLMM (individual identity as random factors). Thelargest overlap for all years pooled was observed with the pelagicand , demersal coastal fleets (UDOI ≥ 0.32) and ice-trawl targethake (≥ 0.25). For immatures ice-trawl target hake (2006 and2008-2009 periods), freezer longliners (2006) and coastal demersaltrawl (2009-2010 period) werethe fisheries that showed positive effect in the foraging behavior (i.e. foraging was most likely with increased fishing effort), whilefor adults ice-trawl target hake was the only fishery with effectsignificantly positive This preliminary analysis as a proxy of riskof interaction constitutes the basis for further studies to defineareas and times of higher sensitivity for shearwaters attending fisheries.