Description of food sources used by jumbo squid Dosidicus gigas (D’Orbigny, 1835) in Ecuadorian waters during 2014

• The diet of Dosidicus gigas in the waters of Ecuador was mainly composed of myctophid fish.
• Three squid families, Ommastrephidae, Gonatidae, and Onychoteuthidae, were identified in the stomach contents of Dosidicus gigas.
• Evidence of cannibalism was found in stomach contents of Dosidicus gigas, and can be attributed to the trammel net method used by the artisanal fishermen.

Jumbo squid, Dosidicus gigas, is a species endemic to the eastern Pacific. Its distribution ranges from the Gulf of Alaska to Chile. These squids are important components of the ecosystem, as they are prey to sharks, billfishes, and marine mammals, and active predators of myctophid fishes, other squids and crustaceans. In Ecuador, D. gigas is a potential resource for industrial and artisanal fisheries, but they are often by-catch in artisanal fisheries that use trammel net and gill-netting methods. Due to the importance of D. gigas as prey and predator, we performed this exploratory research to describe the composition of their diet and identify their most important prey. A total of 167 squids were sampled in Santa Rosa, Salinas, Ecuador from May to December 2014. Squids ranged between 17.5 and 52 cm ML, and our results showed an average size of 40 cm ML. According to the %IRI the diet was mainly composed of fish and squids. Two myctophids, Lampanyctus sp. and Myctophum sp., were important food resources. Our results showed that there was no difference between food resources, and the sex, size, and maturity of squids in our sample. Cannibalism also occurs on small to large D. gigas, and is influenced by availability of other prey in the surface waters during fishing activity.