Cephalopod species in the diet of large pelagic fish (sharks and billfishes) in Ecuadorian waters

• Sharks Prionace glauca, Sphyrna spp., and Isurus oxyrinchus, and the swordfish Xiphias gladius are active predators of cephalopod species in the Ecuadorian Pacific.
• Squids (Teuthida) are predated by apex predators in the area, and they are key species in the trophic web of the ecosystem.
• Xhipias gladius and Prionace glauca are the most important predators of cephalopods in Ecuadorian waters, and D. gigas is their main prey.

Large pelagic fish species are apex predators in the ecosystem of the Pacific Ocean, and they represent important economic resources for fisheries. In Ecuador there is a fishery for billfish such as Istophorus platypterus, Xiphias gladius, Makaira nigricans, and Kajikia audax, in which sharks such as Prionace glauca and Isurus oxyrinchus are also caught. Their prey includes small fish and cephalopods. We studied the trophic ecology of sharks and billfish captured in Santa Rosa (Salinas) and Playita Mía (Manta) Ecuador during 2013 and 2014, in order to evaluate their trophic relationship with different cephalopod species. Our results show that cephalopods are the most important prey in the diet of sharks (%IRI = 61.6) and billfishes (%IRI = 77.5). Twenty two species of cephalopods of the Orders Octopoda, Vampyromorphida and Teuthida were identified in the stomach contents, with Dosidicus gigas, Ancistrocheirus lesueurii and Histioteuthis dofleini being the most important. We also demonstrated that squid are abundant in waters off Ecuador. The ommastrephid D. gigas was the main prey for billfish (%IRI = 93.7 for X. gladius) and the second most important for sharks (%IRI = 44.9 for I. oxyrinchus). Cephalopods are key prey items for predatory pelagic fish in the Pacific Ocean off the coast of Ecuador. Further studies on the diet of these fish species are needed to better understand their role as top-level predators in the marine food web and to improve knowledge of the diversity of cephalopods in the region.