Geographic distribution of the short-tailed river stingray, Potamotrygon brachyura: assessing habitat loss and fishing as threats to the world's largest obligate freshwater elasmobranch

LUCIFORA L. O.; BARBINI, S. A.; LLAMAZARES VEGH, S.; SCARABOTTI, P. A.; VARGAS, F.; SOLARI, A; MABRAGAÑA E.; DÍAZ DE ASTARLOA, J. M.

MARINE AND FRESHWATER RESEARCH

CSIRO PUBLISHING

Lugar: Collingwood; Año: 2015 vol. 67 p. 1463 - 1478

1323-1650

Freshwater elasmobranchs are imperiled but largely unknown. Potamotrygon brachyura is the world´s largest obligate freshwater elasmobranch. This makes it popular among fishermen and suggests a susceptibility to anthropogenic threats. We collected records of P. brachyura (n=70) from media, fishermen and scientific sampling, to estimate its global geographic distribution (using both generalized additive and MaxLike models). Then, we estimated the species´ exposure to habitat modification and fishing pressure, by applying multinomial ordinal models with threat levels as response and presence/absence of P. brachyura as independent variable. Distance to coast, depth, water temperature and salinity ranges, and mean water temperature were the main determinants of the distribution in the Río de la Plata (RdlP). This resulted in a narrow coastal distribution. In the Uruguay and Paraná river basins (UP), probability of occurrence was positively associated to flow accumulation, percentage of open water and submerged vegetation, and lowland ecoregions, and negatively to wetness index and altitude. This limited the distribution to large lowland rivers. Approximately 41% of P. brachyura´s RdlP range was subject to high habitat modification. In UP, this percentage reached to 7%, however, the overlap with high fishing pressure was 59%. Biogeographic methods can inform the conservation status of freshwater elasmobranchs.