The eastern Pacific jumbo squid (Dosidicus gigas) is one of the largest and most abundant squid of the world ocean. To reveal possible interannual variability in the life span, statoliths were used to determine the age of mature females belonging to two modal size groups (<490 and >500mmmantle length) collected before (1991-1996), during (1997-1998), and after (1999-2011) a strong El Nino event in Peruvian waters. We found that water temperatures encountered between the third and sixth months of ontogenesis had the strongest negative effect on age. Together with a weaker but significant negative effect of temperatures encountered during early life (first to third months) and later ontogenesis (seventh and eighth months), these temperature parameters (along with other environmental factors) were important in determining whether a given animal had a 1-year life cycle (early maturation and small size) or a 1.5-to 2-year life cycle (delayed maturation and large size). The possible cause of a sudden increase in abundance of large D. gigas in 2000-2001 is discussed.