Jumbo flying squid in the Eastern Pacific inhabits open waters of the ocean during certain phases of its ontogeny, as well as in outer shelf and continental slope waters from subpolar to tropical climatic zones in Northern and Southern hemispheres (Nigmatullin et al. 2001). Genetic studies suggest that the NE Pacific and SE Pacific represent genetically different stocks with some migration within them, with the single large metapopulation in the southeastern Pacific that experienced a dramatic expansion associated with the rise in sea surface temperature (Sandoval-Castellanos et al. 2010, Ibáñez et al. 2011; Ibáñez and Poulin 2014).

In the SE Pacific, different groups have been identified based on size at maturity. Earlier research suggested that there are three phenotypic groups of jumbo squid distinguished by their sizes at maturity, small (females ranging 14 to 34 cm mantle length, ML), medium-size (28 to 60 cm ML), and large-size groups (55 to 120 cm ML) (Nigmatullin et al. 2001). Other authors suggested the existence of just two phenotype groups or size forms, medium-size (<49 cm ML) and large form (>52 m ML) (Argüelles et al. 2001). Water temperatures encountered by jumbo squid juveniles are important to determine whether a given animal has a 1-year life cycle (early maturation and attaining small or medium sizes), or a 1.5-2-year life cycle (delayed maturation and large size). Thus, a water temperature ‘switch’ at the juvenile ontogenetic phase channels the further development of an individual animal into either a small-medium form or a large form (Arkhipkin et al. 2015).