The Phylogeny, Biology and Conservation Status of Freshwater Stingrays (Family Potamotrygonidae) in South America and Recommendations for Future Conservation

Defense Date


Document Type


Degree Name

M.S. Marine Biology

Second Degree Name

M.S. Coastal Zone Management

First Advisor

Richard Spieler

Second Advisor

Demian Chapman


Freshwater stingrays of the family Potamotrygonidae are found exclusively inSouth Americain a variety of freshwater habitats. They are particularly susceptible to a variety of anthropogenic stresses because they are located so close to human settlements and thus suffer from fishing pressure (pollution, habitat degradation) and habitat loss (development). Little is known about these animals, but there is increasing attention on their conservation status.

Potamotrygonids share the same life history characteristics as their marine relatives (slow growth, late maturity, long gestation, low fecundity, and long life) but differ by having a variety of color morphs within individuals of the same genus, making identification difficult, and a modified osmoregulation system enabling them to live only in freshwater. Despite the need for conservation, very little is known about reproductive processes and ecology of most potamotrygonids.

The current state of potamotrygonid taxonomy and evolutionary history is under debate. Due to the extreme polymorphic variability within a genus, the taxonomy of this family is undergoing constant revision. Multiple hypotheses have been put forth regarding their evolution and appearance in freshwater river systems. The most recent and most probable being a marine incursion during the Early Miocene, resulting in sister taxa in both theAtlanticand Pacific.

Potamotrygonids are exploited for food and the aquarium trade with unknown consequences on wild populations. This exploitation is unregulated in most South American countries making developing management policies and enforcing trade laws difficult. Taxonomic resolution, increased understanding of reproduction and ecology, public education, development of preserves, and captive breeding programs are all recommended to help conserve this unique family of obligate freshwater stingrays.

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