Understanding Pelagic Stingray (Pteroplatytrygon violacea) by-catch by Spanish Longliners from the Mediterranean Sea
The pelagic stingray Pteroplatytrygon violacea is known to be a frequent by-catch in longline fisheries around the world. The aim of this study is to analyse the parameters affecting to the by-catch of pelagic stingray by the Spanish surface drifting longline fleet that operates in the Mediterranean Sea. Since the year 2000 until the year 2013, 3007 longline fishing operations were monitored. In these 14 years, we recorded 57,574 pelagic stingrays by-catches by Spanish longline. Two gear types concentrate 96.05% of pelagic stingray by-catch observed: traditional surface longliners targeting swordfish (LLHB) and surface drifting longliners targeting albacore (LLALB). We obtained two statistically significant explicative models for the gears LLHB and LLALB. In both cases, fisheries over continental shelf and summer variables are important parameters. Furthermore, for the LLHB explicative model included the variables: number of hooks, latitude where the setting started, distance between both extremes of the longline and spring. Moreover, for the LLHB we obtained a relationship between the Capture per Unit of Effort of pelagic stingray from favour sets per year and the North Atlantic Oscillation in winter.