Seasonal migration of North Pacific giant octopus Enteroctopus dofleini in the Soya/La Pérouse Strait

The seasonal migration of North Pacific giant octopus Enteroctopus dofleini in the Soya/La Perouse Strait was investigated using GPS location information of octopus catches by drift fishery boats. Body weight and stage of maturity of the collected octopuses were recorded. Immature octopuses were found at depths of 40 to 60 m in summer and 10 to 30 m in autumn to spring. Although mature octopuses were observed at the same depths as juveniles in most months, in June and July, mature males and females migrated to deeper areas immediately before death and spawning, respectively. Based on bottom water temperatures in areas where the octopus was distributed, it appears that this species migrates to deeper areas to avoid water temperatures above 18 degrees C.