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The food habits of the South Pacific hake (Merluccius gayi) from Ecuadorian waters were studied by analysing 232 stomachs of specimens ranging from 23.4–83.1 cm in total length (TL). Fish was the most important prey group (Alimentary Index, %AI = 94), Ctenosciaena peruviana being the most represented prey species (%AI = 62.17). PERMANOVA analysis showed dietary differences between the smallest individuals (class I < 30 cm TL) and the largest (class IV 40–45 cm TL; class V ≥ 45 cm TL). In addition, spatial differences in dietary composition were found between the three sampled regions (Manabí, Santa Elena and Guayas). The results of this study indicate that the South Pacific hake is an opportunistic predator feeding on a wide variety of vertebrate and invertebrate organisms.

The diet and the feeding habits of the common dolphinfish (Coryphaena hippurus) in the Pacific coast of Ecuador was assessed by examining 320 stomachs of individuals ranging from 51 to 149 cm in total length. Fish was the predominant prey group in the diet (Alimentary Index, %AI = 95.39) followed by cephalopods (%AI = 4.13) and crustaceans (%AI = 0.48). Among the 17 prey items that make up the dolphinfish diet, the Exocoetidae family was the most important prey (%AI = 57.13),Dosidicus gigasbeing the most abundant invertebrate species (%AI = 7.65). Feeding patterns were evaluated using the graphing method of Amundsen, which suggested that this species shows a varying degree of specialization on different prey taxa. Thus, while some species were unimportant and rare (Hippocampus hippocampus, Lagocephalus lagocephalus, Gobiidae andArgonautasp.), several dolphinfishes showed a high degree of specialization on Scombridae,Pleuroncodes planipes, Portunus xantusiiandOpisthonema libertate. Size-related and temporal shifts in dietary composition were investigated by PERMANOVA analysis, which showed wide variations among size classes and periods of capture. The results of this study indicate that the common dolphinfish is an opportunistic feeder, which is capable of consuming a wide variety of schooling epipelagic organisms.

The diet of young Atlantic bluefin tuna (Thunnus thynnus) in the Bay of Biscay foraging ground was assessed using stomach-content analysis (SCA) and stable-isotope analysis coupled with isotope mixing model. Whereas SCA showed that the young tuna fed mainly on horse mackerel (Trachurus trachurus), the estimation of liver and muscle mixing model analyses indicated that northern krill (Meganyctiphanes norvegica) was the most important food resource. These contrasting observations are probably due to the different time scales spanned by the different methods. The present results suggest that young bluefin tuna prey at different trophic levels of the Bay of Biscay pelagic food web, thus behaving as an opportunist and generalist predator.