Influencia del tiempo de permanencia del aparejo en el agua sobre la captura accesoria del palangre semi-pelágico

The purpose of this study is to analyze the influence of the time the gear remains in the water (hereafter “soak time”) in the by-catches of the semi-pelagic longline fisheries targeting swordfish in the western Mediterranean and its impact on the conservation of biodiversity. For this, a soak time was assigned to each section of longline. The soak time was calculated as the difference between the time of setting and the time of lifting of each section. Then the differences between time bands were tested by the U de Mann-Whitney text; the relation between soak time and the catch rates were tested by curvilinear estimation models. Lastly, to assess the impact of soak time in the conservation of biodiversity, the Fattorini index (Biodiversity Conservation Concern index) was used. Relationships were found between the catches per unit of effort (CPUE) and soak time. The highest by-catch rates were found in the sections of intermediate duration. However, for swordfish catches larger than the size at first maturity the catch rate increased asymptotically as the soak time increased. For swordfish smaller than the size at first maturity, the CPUE is directly proportional to the soak time. The major impact on the conservation of biodiversity corresponded to the longline sections with an intermediate soak time.