Data for: Stable isotopes in eye lenses reveal migration and mixing patterns of diamond squid in the western North Pacific and its marginal seas

Knowledge of the movements of marine organisms is essential for effective
conservation schemes. Here, we investigated the lifetime habitat use of
diamond squid, Thysanoteuthis rhombus, collected in the western North
Pacific and its marginal seas (the Sea of Japan and the East China sea)
during 2021–2022, whose migratory ecology is poorly known, using bulk
stable nitrogen and carbon isotope ratios in eye lenses. From the eye lens
isotope profiles, the chronology of the isotopic baseline of squid habitat
was estimated by removing the effect of size-dependent changes of trophic
position. Then, the baseline estimates were compared to the isoscapes of
particulate organic matter. The baseline chronologies showed fluctuations
during the paralarval and juvenile stages, becoming stable during the
adult stage, suggesting that significant movements mainly occur during the
early life stages due to current transport, with adults potentially not
undertaking long-distance migrations. The squids in the marginal seas
mostly originated from outside the subtropical gyre, while the squids in
the subtropical gyre had various sources, including outside the gyre and
southern and northern parts within the gyre, revealing a complex mixing
pattern of the species. These results show that isotope chronology
combined with baseline isoscapes are effective tools to understand animal
migrations, which can help to manage various cephalopods and fishes.