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Pelagic predators such as sharks have been shown to be effective cephalopod samplers, because they have high consumption rate sand swimming speeds.The stomach contents of these predators allow us to determine the distribution and abundance of cephalopods, considering the scarcity of biological information and the difficulty of catching squids and octopus in traditional methods.The silky shark(Carcharhinus falciformis), blue shark (Prionace glauca), scalloped hammer head (Sphyrna lewini), smooth hammer head (Sphyrna zygaena), pelagic thresher shark (Alopias pelagicus), and big eye thresher shark (Alopias superciliosus) were caught off both coasts of Baja California Sur, Mexico, and in the Ecuadorian Pacific Ocean. Cephalopod sizes (mantle lengths, ML) were calculated based on the beak measurements to determine the size of cephalopods consumed by the sharks. We identified 21 cephalopod species based on beak items found in the shark stomachs.The most abundant cephalopods consumed by sharks in both areas were Dosidicus gigas, Ancistrocheirus lesueurii, Onychoteuthis banksii, Sthenoteuthis ovalaniensis, Argonauta spp., Abraliopsis affinis, and Mastigoteuthis dentata. The cephalopod's habitat provides information about hedep that which these sharks capture their prey.The blue shark feeds on cephalopods in epipelagic, mesopelagic, and bathypelagic waters; the silky shark feeds on cephalopods in epipelagic waters; and the scalloped hammerhead shark preys on cephalopods in neritic (bottom) and oceanic waters (epipelagic and mesopelagic).The pelagic thresher shark consumed epipelagic and neritic species; where as the big eye thresher shark feeds mainly on epipelagic and mesopelagic squids in Ecuadorian waters. The smooth hammer head preys on epipelagic and mesopelagic squids off Mexico and Ecuador.

Palabras clave: vertical distribution; Sharks; estructura termohalina; Squid.; Ecuador.

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