Population dynamic studies of Dosidicus gigas have not been reported in Ecuadorian waters. The number of cohorts in the population and reproductive features such as sex ratio, seasonal changes in maturity stages, and size at first maturity are unknown. This knowledge is crucial in the study area, because it can provide fishery management support to Ecuadorian stakeholders. Biological data from 2013 (March–December) and 2014 (January–December) in Ecuadorian waters were analyzed. Biological sampling per month was carried out during every year in different coastal waters off of Ecuador. The biological findings indicated the presence of three size groups in the Ecuadorian squid stock, which estimated to be individuals less than 50 cm mantle length (ML). The monthly size groups changed between one and three size groups in 2013 and 2014. The ML at first maturity for females of jumbo squid estimated in 2013 was L_50% = 32.4 cm ML, and L_50% = 35.5 cm ML in 2014. For both fishing seasons, the ML-mantle weight relationship estimated for jumbo squid presented isometric growth, and the sex ratio for D. gigas showed that females were more abundant than males. This study found that the ML structure of jumbo squid, the number of size groups, and ML at first maturity are different from that previously estimated in traditional fishing areas of D. gigas in the eastern Pacific Ocean.