Predicting and contextualizing sensitivity to overfishing in Neotropical freshwater stingrays (Chondrichthyes: Potamotrygonidae)

Abstract

Neotropical freshwater stingrays (Potamotrygonidae) are conspicuous components of the South American ichthyofauna, and may be regionally important as an economic resource. The smallest individuals are exploited in ornamental fisheries, while large individuals are caught in consumptive fisheries for their meat or liver oil. Potamotrygonid life history is poorly known, which complicates fisheries management and conservation. Here, we compiled life history traits of potamotrygonids and predict unknown traits from their relationship with body size, to compute the maximum population growth rate (rmax), a widely-used metric of sensitivity to overfishing. Potamotrygonid rmax was compared with that of marine chondrichthyans and South American crocodylians. Marine chondrichthyans include the closest relatives of potamotrygonids, and South American crocodylians are a group with known overexploitation history sharing the habitat and general life history strategy with potamotrygonids. Simulations for species with known traits indicated that predictions were close to real values and unbiased. Potamotrygonid rmax varied from 0.14 to 0.39, well within the range of marine chondrichthyans (0.03–1.37) and lower than crocodylians (0.23–0.52). Generation time ranged from 6.7 to 19.5 years. These figures indicate that sustainable exploitation of potamotrygonids is possible. However, tight regulations (e.g. size and catch limits) and science-based management are necessary, especially for species with small geographic range, low population size, or low rmax (< 0.2). Empirical studies on potamotrygonid life history and ecology are urgently needed to aid management. Potential scenarios for sustainable exploitation of potamotrygonids are discussed, including ornamental and consumptive fisheries, and sighting-based tourism.