Fontaine, P., Barreiros, J.P. & Jaquemet, S. (2023) Trophic ecology of three sympatric batoid species (Dasyatis pastinaca, Raja clavata, and Raja maderensis) from the Azores, NE Atlantic.Environmental Biology of Fishes, 106, 1477-1492. DOI:10.1007/s10641-023-01412-2 (IF2022 1,4; Q4 Ecology)
Describing the trophic structure and interactions of demersal elasmobranch assemblages is fundamental to understanding food web dynamics and developing ecosystem-based management approaches. Stomach content analysis (SCA) and stable isotope ratios (SIA) of carbon (δ13C) and nitrogen (δ15N) from muscle were used to examine the dietary habits and intra- and interspecific trophic ecology of three sympatric batoid species (Dasyatis pastinaca, Raja clavata, and Raja maderensis) from the Azores, Northeast Atlantic. Data were analyzed with respect to sex and maturity stages. SCA showed that D. pastinaca feeds mostly on crustaceans, whereas R. clavata and R. maderensis prey almost exclusively on teleosts, but not on the same species. Dasyatis pastinaca displayed higher δ13C and lower δ15N values compared to R. clavata and R. maderensis. Trophic niche breadth was variable, D. pastinaca and R. clavata had the broadest and the narrowest trophic breadth, respectively. Relative trophic position categorized D. pastinaca as a mesopredator, while R. clavata and R. maderensis occupied higher trophic positions. With size, R. clavata and R. maderensis shifted from small prey such as crustaceans to larger prey such as teleosts, and they also exhibited significant increases in δ15N with size. Dietary and isotopic overlap was overall low among species, but it was higher between R. clavata and R. maderensis, suggesting more similarity in diet and habitat use between them than with D. pastinaca. This study depicts trophic interactions and functional roles of three co-existing batoid species in the Azorean food webs. In addition to presenting new information on the trophic ecology of D. pastinaca and R. clavata, the present study provides, to our knowledge, the first description of the diet composition and trophic level of the Macaronesian endemic batoid R. maderensis.