Feeding spectrum of squid Sthenoteuthis oualaniensis (Oegopsida) in the eastern Pacific

The stomach contents of 235 specimens of the squid Sthenoteuthis oualaniensis (4·3–36·5 cm mantle length, ML) were examined. A detailed list of 60 species of prey, comprising young and adult squid, is given together with their frequency of occurrence and proportional contribution. The size and number of each food item was investigated. Three ontogenetic size-groups of S. oualaniensis were distinguished: I, fry and young (4–10 cm ML), micronektonic epipelagic plankton-eaters; II, transient critical size group (10–15 cm ML), converting from feeding on planktonic crustaceans and fish larvae to myctophid fishes; III, medium-sized (adult) nyctoepipelagic nektonic predators (15–36·5 cm ML), feeding primarily on myctophids and secondarily on squid. Myctophids (genera Symbolophorus, Myctophum and Hygophum) were the most abundant prey in the diet of adult S. oualaniensis from different parts of its distribution