Feeding habits and ecological role of the freshwater stingray Potamotrygon magdalenae (Duméril 1865) (Myliobatiformes: Potamotrygonidae), combining gut-content and stable isotope analysis

Understanding the ecological role of a species in an ecosystem and the dynamics of the communities depends largely on knowledge of the trophic relationships. We evaluated the feeding habits and the trophic ecology of the endemic Colombian stingray Potamotrygon magdalenae , integrating stomach content and isotopic analyses ( 13 C and 15 N). The samples were collected in the middle Magdalena River basin, Colombia, during artisanal fishing operations in the dry and rainy seasons. The stomach content analysis indicated that P. magdalenae fed on a high number of occasional items, such as seeds, Planariidae, Teleostei and Nematoda, with Diptera being the dominant food component at the population level. There were no significant differences in diet between males and females. In contrast, isotopic analysis showed that Coleoptera was the most important food source assimilated by the species, followed by Ephemeroptera; Chironomidae and Trichoptera made the lowest contributions. No significant differences in δ 13 C and δ 15 N were observed between the sexes or hydrological seasons. Estimates of the isotopic niche indicated that P. magdalenae has a narrower trophic niche than the teleost fishes present in the study area. The trophic level was identified as intermediate, suggesting that Potamotrygon magdalenae plays a role as a mesopredator in the food web in the study area.