Is the tiger shark (Galeocerdo cuvier) a coastal species? Expanding its distribution range in the Atlantic Ocean using at-sea observer data

captura asociada a la pesquería de palangre de superficie dirigida a pez espadaThe occurrence of tiger shark (Galeocerdo cuvier) in the Atlantic Ocean was assessed using at-sea observer data from multiple pelagic longline fisheries (Japan, Portugal, Spain, United States and Uruguay). Geographic positions of 2,764 tiger sharks, recorded between 1993 and 2013 and covering a wide area of the Atlantic were compared with the currently accepted distribution ranges of the species. Most of our records fell outside the accepted distribution ranges in both the Southern and Northern hemispheres. These results strongly suggest that the distribution range of the tiger shark is considerably wider than previously described, particularly over the open oceanEn prensa1,834

Distributional and reproductive aspects of the bigeye thresher shark (Alopias superciliosus) in the Atlantic ocean

Captura asociada a la pesquería de palangre de superficie dirigida a pez espadaThe bigeye thresher shark, Alopias supercilious is sometimes caught as bycatch in pelagic longline fisheries targeting tunas and swordfish in the Atlantic Ocean. As part of an ongoing cooperative program for fisheries and biological data collection, fishery observer data from various fishing nations and projects were compiled and analyzed. Those data sets include information on geographic location of the observations, as well as size, sex and in some cases maturity stage. A total of 4371 bigeye threshers were recorded throughout the Atlantic Ocean between 1992 and 2013, with the sizes ranging from 70 to 305 cm FL (fork length). Considerable variability was observed in the catchat- size, with particular emphasis on the tropical region where the mean sizes tended to be smaller than in the other regions. The expected distribution of juvenile and adult specimens also showed considerable variability, and the sex-ratios varied between regions and size classes. Maturity ogives were fitted to data from 642 specimens, with the median sizes at maturity estimated at 208.6 cm FL (corresponding to 349.1 cm TL) for females and 159.2 cm FL (corresponding to 269.8 cm TL) for males. In addition, a segmented regression model (SRM) was used for males, and two breakpoints (Bk1: 122.5cm FL, Bk2: 173.3cm FL) estimated, identifying transitions between the three different maturity stages for male sharks (immature, maturing and mature). Only a few pregnant females were recorded, always with the presence of two embryos (one per uterus), and were distributed predominantly in the tropical northeast Atlantic closer the African continent, and in the southwest region, with those regions possibly serving as nursery areas for this species. These reproductive parameters, and especially the estimated median sizes at maturity and low fecundity, highlight the vulnerability of this species, reinforcing that the bigeye thresher tends to mature at a larger size than the other species of the Alopiidae family. The biological and distributional patterns presented can help managers adopt more informed and efficient conservation measures for this species.En prensa0,000

Distribution pattern of the blue shark (Prionace glauca) in the Atlantic Ocean from observer data of the major fishing fleets

The blue shark is the most captured shark in pelagic longline fisheries targeting tunas and swordfish. As part of an ongoing cooperative program for fisheries and biological data collection , information collected by fishery observers and scientific Project from several fishing nations in the Atlantic (EU.Spain, EU.Portugal, Uruguay, Taiwán, USA, Japan, Brasil, Venezuela and South Africa) were analyzed. Datasets include information on geographic location, size and sex. A total of 414428 blue sharks records collected between 1992 and 2014 were compiled, with the sizes ranging from 36 to 394 cm FL (fork length). Considerable variability was observed in the size distribution by región and season, with larger sizes tending to ocsur in equatorial and tropical regions and smaller sizes in higher latitudes. The expected distribution of juvenile and adult specimens also showed considerable variability, and the sex ratios varied between regions and sizes classes. The distributional patterns presented in this study provide a better understanding of different aspects of this species in the Atlantic that can help to promote more informed managemente and conservation measures.En prensa0,000