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Food and feeding of jumbo squid Dosidicus gigas in the central gulf of California during 2005-2007

Abstract:

Stomach contents were analyzed for 249 jumbo squid (Dosidicus gigas) of 35-80 cm mantle length. All squid were sampled in the central Gulf of California in 2005-07, primarily on the commercial fishing grounds of Santa Rosalia during different times of the year.Diet off Santa Rosalia was mainly composed of mesopelagic micronektonic organisms, mostly the myctophids Benthosema panamense,Triphoturus mexicanus, and the squid Pterygioteuthis giardi. Pteropods and crustaceans made up a smaller portion of the diet. Squid sampled elsewhere revealed that the pelagic red crab, Pleuroncodes planipes, and northern anchovy, Engraulis mordax, could also be major dietary items. Cannibalism incidence increased with squid mantle length.We propose that the main prey of jumbo squid in the central Gulf of California derives from the mesopelagic community associated with the upper boundary of the oxygen minimum layer, a welldeveloped midwater feature in this region. In addition, opportunistic foraging on a variety of organisms supplements their dietary intake. These data are discussed in conjunction with recent electronic tagging data that revealed vertical and horizontal movements of jumbo squid. This work demonstrates a need to study the dynamics of the oxygen minimum layer and the composition of the deep-scattering layer over the upper slope of Guaymas basin.