DECLINE OF SOUTH AMERICAN RIVER STINGRAYS WORRIES RESEARCHERS
Despite elasmobranchs, as sharks and rays are a predominantly marine species, many of them are regularly found in fresh water. Although there is ample evidence of declining elasmobranch populations around the world, this evidence comes almost exclusively from marine species; the ecology and conservation status of obligate freshwater elasmobranchs is far from being understood.
River stingrays live exclusively in South American rivers and represent the overwhelming majority of freshwater elasmobranch diversity, with 32 species known so far. Now reseachers present evidence of a decline in the abundance of river stingrays in the middle and lower Paraná River, an extensive wetland mosaic of approximately 35,000 km2 .
By taking advantage of stingray tail mutilation, an extended practice among South American fishermen, researchers estimated the population and spatial differences in relative fishing pressure, they found that the observed decline is related to fishing pressure. The highest fishing effort and lowest relative abundance occurred in areas where fisheries operate on the river floodplain. The lowest fishing effort and highest relative abundances occurred in areas where fisheries operate in the main channel.
This evidence confirms the vulnerability of river stingray, and another freshwater elasmobranchs, caused because overfishing, and suggests that some species can be exploited sustainably. According to researchers, negative effects on freshwater elasmobranchs can be minimized by adjusting fishing grounds
image: Amanda's river stingray (Potamotrygon amandae), picture taken in the Corriente River, a tributary of the Paraná River in Argentina by Matías A. Lipsker.
Reference: Lucifora et al., 2017. Decline or stability of obligate freshwater elasmobranchs following high fishing pressure. Biological Conservation.
