The composition of diets suggests that all elasmobranchs studied are species that feed on epibenthic invertebrates (mainly stomatopods and decapods) and fish. This result is highly associated with the source of the samples analyzed, i.e., elasmobranchs captured in bottom trawl fishery. Predators found during this activity, feed mainly on benthic infauna (prey species living in the sediment), epibenthic fauna (prey species living on the surface of the sediment), benthic prey (prey species living on the bottom) or demersal prey (prey species living near the bottom but not linked to it). Therefore, the results of this research are restricted to elasmobranchs that feed on prey species living on the sediment surface or inside the sediment. However, our results contribute significantly to increase the knowledge on the feeding ecology of the other 138 species of fishes coexisting in the same habitat , with similar food and space requirements.
Mustelus species have been reported to feed mainly on crustaceans and fish [18, 25, 26, 32], although cephalopods would also be important in their diets . Despite the large number of taxa found in the stomach contents of M. lunulatus, one species of stomatopod accounted for most of the prey consumed (stomatopoda = %IRI = 96.9). Therefore, M. lunuatus in coastal waters of the Colombian Eastern Tropical Pacific have a specific dietary preference. Besides Ellis et al. , this is the only other report of feeding specialization in Mustelus, a genus that has been classified as opportunistic polyphagous [34, 35].
The diet of Raja velezi in the neritic zone of the Eastern Pacific Ocean of Colombia showed a low number of prey items in compared with other studies [20, 36, 37] that found polychaetes, copepods, amphipods, Myscidacea, stomatopods, cephalopods and bivalves. However, the preference of R. velezi to feed on decapods and fishes detected in this study was similar to that reported for R. naevus , R. clavata , R. radiata , and R. brachyura, R. montagui and R. eglanteria , which also feed upon decapods or fish. Although R. velezi is a deep-water ray with a widespread distribution, our results are the first description of the diet of this species in the Tropical Pacific Ocean. Rhinobatos leucorhynchus has been identified as a crustacean predator, with preference for penaeid shrimp [22, 34, 40, 41], although portunid crabs have also been reported as alternative prey .
Very little is known of the diet of Dasyatis longa and Zapteryx xyster and this study is the first record on the diet of these species. Similar to other benthic species Dasyatis longa feed on crustacean decapods (stomatopods) and fishes. The preferences for these dietary items have also been reported for Dasyatis americana in the Caribbean Sea . Zapteryx xyster showed the widest feeding spectrum of all elasmobranch studied. This species included stomatopods, decapods and fishes in its diet and, was the most generalist species. Bornatowski et al.  reported similar results for Z. brevirostris from South Brazil.
Macpherson  and Cortés  suggested that the relatively big body size of elasmobranch makes it easy for them to expand their feeding spectrum, preying simultaneously on the pelagic and benthic communities. Our study shows that diet breadth was reduced, and prey item distribution by number and weight were similar. Moreover, all studied elasmobranch fed on three main items: Squillidae, Penaeidae and fish. This can be explained by the benthic habits and similarity of sizes and dental structure between M. lunulatus and D. longa, as well as between Rhinobatos leucorhynchus, Raja velezi and Z. xyster.
The complete dietary overlap detected between M. lunulatus and D. longa, their similar geographical distribution in the study area, and their diurnal activity, suggest that these species could show a competitive exclusion trend for food resources .
However, the dietary overlap would be reduced when the deep distribution is considered because M. lunulatus occupies deep waters and D. longa shallow waters. In contrast the dietary overlap detected between Rhinobatos leucorhynchus, Raja velezi and Z. xyster would be significant, since these species have morphological (size and position mouth) and behavioral similarities.
The dietary overlap between Rhinobatos leucorhynchus – Raja velezi and R. leucorhynchus – Z. xyster, based on the presence of Trachypenaeus shrimp and fishes, could be compensated by differential diel feeding activity. Rhinobatos leucorhynchus feed mainly during the day whereas R. velezi and Z xyster feed manly at night. Furthermore, 89% of Rhinobatos whose stomachs were analyzed were caught at a deep of 15–30 m, whereas all Raja and Zapteryx specimens were caugth at a depth of 40 m. In contrast, the dietary overlap between R. velezi and Z. xyster, species with similar feeding activity and bathymetric distribution, suggests that they share only a fraction of their feeding niche, protecting a portion as an uncontested space refuge . In this sense, mantis shrimp would be the feeding refuge of Z. xyster. Dietary overlap between Z. xyster and R. velezi was fish unidentified and decapods; however this food category was so indeterminate that the evidence of effective dietary overlap is weak. Furthermore, this wide category of prey item overestimate dietary overlap and underestimate niche breadth.
Values of overlap based on simulations suggest that the species studied showed low dietary overlap (mean = 0.44). In this study only five species of elasmobranchs were examined. In the study area at least another 12 species of elasmobranchs [31, 48] and six species of fishes  that share morphological and ecological characteristics with the studied species have been reported. However, all these species and the elasmobranchs that we studied would conform apackaging throughout a feeding axis, and the temporal dynamics of this packaging could be determined by: (i) variety and productivity of available resources, (ii) short-term and long-term environmental variability, and (iii) niche overlap [49, 50]. Therefore, if the packaging is modulated by resource availability  then the shrimp trawl fishery in the neritic zone of Eastern Pacific of Colombia has severely affected the natural availability of prey for elasmobranch communities [51, 52], affecting their structure.