Characterization of the northernmost spawning habitat of Dosidicus gigas with implications for its northwards range extension

The jumbo squid Dosidicus gigas is an ecologically and commercially important species whose northernmost geographic limit is the Gulf of California. However, over the last decades this species has extended its geographic distribution polewards, with associated impacts on the ecosystem. The origin of range-shifting individuals is poorly understood; therefore, we aimed to identify and characterize the northernmost spawning habitat of this species. Implications of the location and oceanographic conditions of the spawning habitats, migration capacity and life history characteristics of D. gigas are also discussed to elucidate its migration pattern. The northernmost spawning area was located between the biological activity centres (BACs) around the Gulf of Ulloa at the west coast of southern Baja California Peninsula during winter, summer and autumn 2005. Generalized linear models indicated that the interaction of sea surface salinity and thermocline depth, and the effect of latitude and sea surface temperature explained most of the variability in paralarval presence, whereas chlorophyll a and latitude explained paralarval abundance. Simulations indicated that paralarvae were dispersed towards the southwest or temporarily remained between BACs. The northwards incursion of D. gigas may be favoured by BACs and upwelling events along the coast of the northeastern Pacific. In warm years, D. gigas is likely to spawn off the Baja California Peninsula, it may actively migrate as far north as Alaska (USA) tracking BACs and upwelling conditions in search of feeding grounds, and it may return from different areas along the northeastern Pacific to spawn off the Baja California Peninsula.