Trophic ecology of the blotched stingray, Urotrygon chilensis (Elasmobranchii: Myliobatiformes: Urotrygonidae), in three areas of the Mexican Pacific

Abstract

Background. There is a current global consensus that to achieve a sustainable use of fisheries resources, management of every organism subject to exploitation is required rather than only those targeted directly by the fisheries. Further understanding the feeding habits of the species in the ecosystem as well as the predator–prey relationships and their trophic levels is crucial. Batoids occupy an important ecological niche as benthic predators in estuaries and bays. There is no directed fishery for the blotched stingray, Urotrygon chilensis (Günther, 1872), but it is commonly caught incidentally by trawl and bottom gillnets fisheries subsequently diminishing its population. Recently, artisanal fisheries in Mexico have become focused on batoid species due to the depletion of shark catches, although there are few studies on its biology and ecology. Materials and methods. We analysed the trophic ecology of the blotched stingray in two main areas from the Mexican Central Pacific to understand the species’ diet and detect possible differences throughout fishing areas using stomach content analysis. We analysed the overlap in diets between areas and the trophic level at each area. Results. We analysed 423 specimens and found 15 prey groups. Representatives of the two crustacean higher taxa—Cladocera and Peracarida were the most important food items in the north area, while the crustacean family Penaeidae was the most important in the south area, having no significant overlap between areas (Cλ = 0.33). The estimated trophic position for the blotched stingray was 3.51–3.56 in both areas, and according to the Levin’s index, the range of the trophic niche breadth for the blotched stingray was 0.059 and 0.039, which indicates that it is a specialist predator. Conclusion. The blotched stingray is a specialist predator that can adapt to different prey depending on which organisms are present in the ecosystem. It is necessary to continue with these types of studies for the other species inhabiting the area, in addition to monitoring fisheries landings, fishing effort, and variations in biotic and abiotic factors in the area over a long period. However, this study outlines an approach for reaching the ultimate goal of sustainable exploitation of marine resources on an ecosystem level.