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.; 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: 2016 vol. 67 p. 1463 - 1478

1323-1650

Freshwater elasmobranchs are threatened but little is known about them. Potamotrygon brachyura is theworld?s largest obligate freshwater elasmobranch. This makes it popular among fishermen and suggests a susceptibility toanthropogenic threats. We collected records of P. brachyura (n¼70) from media, fishermen and scientific sampling, toestimate its global geographic distribution (using both generalised additive and MaxLike models). Then, we estimated thespecies? exposure to habitat modification and fishing pressure, by applying multinomial ordinal models with threat levelsas response and the presence or absence of P. brachyura as an independent variable. Distance to coast, depth, watertemperature range, salinity range and mean water temperature were the main determinants of the distribution in the Rı´o dela Plata. This resulted in a narrow coastal distribution. In the Uruguay and Parana´ River basins, the probability ofoccurrence was positively associated with flow accumulation, percentage of open water and submerged vegetation, andlowland ecoregions, and negatively to wetness index and altitude. This limited the distribution to large lowland rivers.Approximately 41% of the range of P. brachyura in the Rı´o de la Plata was subject to high habitat modification. In theUruguay and Parana´ River basins, this percentage reached 7%; however, the overlap with high fishing pressure was 59%.For conservation purposes, P. brachyura may function as an umbrella species.