Reproductive biology of jumbo squid Dosidicus gigas in the Gulf of California, 1995-1997

A large-scale, artisanal fishery for jumbo squid (Dosidicus gigas) occurred in the central Gulf of California between 1995 and 1997, mainly off Santa Rosalia and Guaymas, two areas of alternate seasonal upwelling. The fishery was supported mainly by large individuals: females maturing at 750 mm ML a nd males maturing at two sizes, 530 and 670 mm ML, respectively. A medium-s ized maturing group was also detected; 400 nun ML for females and 330 mm ML for males. The 77% of females (909 in total) were immature or maturing ani mals, while 77% of males (392 in total) were mature. The predominance of ma ture males relative to mature females suggests that the central Gulf of Cal ifornia is a feeding ground, although size selection by jig is difficult to assess. The alternate upwelling system could provide a food supply for the maturation of squid all year round. The reproductive season appears to spr ead throughout the year, with a small proportion of mature females and most of the males mature in most months. No spawning peaks could be detected, i ndicating that reproduction probably takes place outside the areas studied. The population size structure was similar for the three fishing seasons co nsidered, indicating a similar use of the upwelling areas for feeding. (C) 2001 Elsevier Science B.V. All rights reserved.