MEPS 400:127-141 (2010)  -  DOI: https://doi.org/10.3354/meps08386

ABSTRACT: Dosidicus gigas is a monocyclic ommastrephid squid and is an important component of its ecosystems in the Eastern Pacific Ocean. The species shows variable reproductive characteristics; among these are 3 spatially separated groups of size-at-maturity. Biological data from the industrial fisheries of the Peruvian Humboldt Current System (HCS) from 1991 to 2007 were analyzed. Changes in reproduction patterns allow jumbo squid to cope with productivity changes in their environment. In the HCS, low productivity is related to warm water masses prevailing during warm periods, and high productivity is found for cool water masses during cool periods. Three general  features related to reproduction enabling the squid to adjust to changes have been identified: (1) variable size-at-maturity, (2) temporal decoupling of male and female formation of reproductive tissue in order to temporally distribute the required energy and (3) changing sex-ratios. Smaller sizes-at-maturity are found in warm water masses, specimens maturing at larger sizes in cool water masses. Females mature at the end of their life which leads to a j-shaped increase in maturity when plotted against mantle length, while males mature at a medium size which results in an s-shaped form of maturation. The 3 groups of size-at-maturity proposed in earlier studies may not actually exist, and may only be an observational artifact from a continuous change in size-at-maturity between 2 extremes.

KEY WORDS: Dosidicus gigas · Cephalopoda · Reproductive patterns · Interannual variability · Size-at-maturity · Energy availability · Peru