Migration, Distribution and Growth Patterns of the North Pacific Giant Octopus <I>Enteroctopus dofleini</I> in Waters Adjacent to Tsugaru Strait

Noro Kyosei, Sakurai Yasunori

doi:10.11233/aquaculturesci.60.429

Migration, distribution and growth of Enteroctopus dofleini (Wülker, 1910) were investigated in waters adjacent to the Tsugaru Strait by release of tagged specimens and comparison with those obtained from fisheries recaptures. A total of 1,190 individuals were recaptured between 1986 and 2007. The initial mean body weight of recaptured specimens at their release was 1.6±0.7 kg (range: 0.1-7.7 kg); mean body weight at recapture was 5.9±4.6 kg (range: 0.7-37.0 kg); and mean elapsed days between release and capture was 174±132 days (range: 2-1,062 days). In terms of horizontal migration, the rate of recapture at the same release station (or in a nearby locality) was high; and 13.5% of individuals obtained on the Honshu side crossed the Tsugaru Strait and migrated to their site of recapture on the Hokkaido side. Considering vertical distribution, octopuses were recaptured from depths of 2 m to 350 m, migrating to deeper areas with increasing growth during the summer. The factor of deeper distribution in summer is affected by the high sea water temperature at this time of year in the Tsugaru Strait. The growth rate was lower in larger specimens of both sexes. From measurements of body weight and tagging results, the specimens were classified into four groups, reaching mature size in 2, 3, 4 or 5 years.

Migration, Distribution and Growth Patterns of the North Pacific Giant Octopus <I>Enteroctopus dofleini</I> in Waters Adjacent to Tsugaru Strait

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