Assessing River Jewels

Adult specimen of the Reticulate Freshwater Stingray (Potamotrygon orbignyi) on a sandy river beach. Region Update: South America

Photo by Patricia Charvet

IUCN SSC Shark Specialist Group | South America Regional Group | Member Programa de Pós-Graduação em Sistemática, Uso e Conservação da Biodiversidade (PPGSis), Departamento de Biologia, Universidade Federal do Ceará (UFC), Fortaleza, CE, Brazil.

IUCN SSC Shark Specialist Group | South America Regional Group | Regional Vice-Chair Programa de Pós-Graduação em Sistemática, Uso e Conservação da Biodiversidade (PPGSis), Departamento de Biologia, Universidade Federal do Ceará (UFC), Fortaleza, CE, Brazil Laboratório de Ecologia e Conservação, Programa de PósGraduação em Engenharia Ambiental, Departamento de Engenharia Ambiental, Universidade Federal do Paraná (UFPR), Curitiba, PR, Brazil.

Adult specimens of the Xingu Freshwater Stingray (Potamotrygon leopoldi), one of the most valued species in the ornamental trade.

Elasmobranchs are known mainly for their marine and estuarine representatives; however, there is an existent lineage that successfully colonized South American freshwater environments. The subfamily Potamotrygoninae, or Neotropical Freshwater Stingrays, comprises 38 described species. These species are distributed in the main water basins and sub-basins of South America. Like many other elasmobranchs, they have low fertility, late maturity, and long lifespans. Those features make them susceptible to fisheries and environmental impacts.

The Potamotrygoninae species are exposed to an array of threats. Attractive and striking dorsal color patterns are a feature for some species that make them a target for the ornamental trade. Their sustainable exploration is always a challenge and a threat for this group. They are known as “river jewels” by many ornamental traders. Some species are also fished for consumption, and it is alarming the increase in fishing pressure in some areas. Moreover, habitat degradation by mining, agriculture (silting, agricultural chemicals runoff) and damming in different regions are also rising concerns. Climate change impacts on droughts, rainfall, and consequently on riverine water level affect the species since all species studied to date have their life cycle associated with flood-drought river dynamics.

There are very few conservation actions in place for these species with most being at countries’ national level (e.g. ornamental trade export quotas). At the request of Brazil and Colombia, several Potamotrygonidae (23 species in Brazil and 8 in Colombia) were listed on the Convention on International Trade in Endangered Species of Flora and Fauna (CITES) Appendix III after having been identified as in need of trade controls. For half of these species, the risk of extinction had not been previously evaluated, while others had been assessed as Data Deficient (DD) on the IUCN Red List of Threatened Species. At the end of 2020, the IUCN SSC Shark Specialist Group established a partnership with the IUCN Freshwater Biodiversity Unit (IUCN FBU) to help carry out the Potamotrygoninae assessments, especially because additional support was needed to map and calculate areas and extent of occurrence. South American specialists on freshwater stingrays were invited to help, contributing with their knowledge on the distribution, life history, threats and much other essential information needed to assess these river jewels.

This international working group is currently assessing the extinction risk of 38 potamotrygonins to have these evaluations ready by the end of 2021. The results will be an essential tool for helping develop management and conservation actions, hopefully ensuring the continuity of this unique evolutionary lineage.