The trophic spectrum of both Eucinostomus entomelas and Micropogonias megalops, the two most abundant fish species in Laguna Las Guásimas, Sonora, México is described in our study. A total of 21 types of prey were identified belonging to seven taxonomic groups (Crustacea, Mollusca, Annelida, Rhodophyta, Copepoda, Echinodermata and Chordata) to analyse the feeding spectra and diet breadth. The preferred prey items of Eucinostomus entomelas (Dark-spot mojarra) were Polichaeta (index of relative importance = 46.7%), followed by bivalves (36.6%), and Luidia columbia (5.6%), while those of Micropogonias megalops (Bigeye croaker) were Portunidae (22.8%) followed by Gammaridae (20.55%) and Crustacea (18.37%). The trophic spectrum for male E. entomela was composed of Bivalvia and Polychaeta. Both predators showed low values in diet breadth (E. entomelas (Levin's index Bi = 0.14) and M. megalops (Levins's index Bi = 0.43)). The low trophic overlap (Cλ = 0.14) between predators suggests that both fish are not competing with each other for food resources in Laguna Las Guásimas.
