Thermal histories reveal spatiotemporal distribution and population overlapping of Sepioteuthis lessoniana

Thermal histories describe ambient temperature experienced by cephalopod species from birth to death, reflecting their habitats and distributions. Thermal histories were reconstructed by analyzing ontogenetic oxygen isotopes (δ18O values) in statoliths of adult Sepioteuthis lessoniana collected from northeastern and southwestern Taiwan between 2017 and 2019. The probabilities of occurrence associated with thermal histories in the two populations were modeled using a spatial interpolation approach, ordinary kriging method. The northeastern population exhibited larger ontogenetic variations in experienced temperature (ranging from 9.1 to 10.4°C) than did the southwestern population (ranging from 4.3°C to 6.8°C). The two geographical populations exhibited distinct ontogenetic movement patterns and distribution. The southwestern population demonstrated wide dispersal influenced by seasonal wind directions and tended to remain in 20°C isotherm areas around the Penghu Islands for maturing and spawning. At the seasonal cohort level, the northeastern population exhibited a southward shift during the 2-year study period as a result of the El Niño event. The distribution of the two geographical populations overlapped in the adult stage primarily in the northern Taiwan Strait, supporting an assumption of population connection in Taiwan. This study revealed the thermal histories of S. lessoniana, providing insights into the field observation of distribution patterns and the progress in relating population dynamics to environmental variability, which are essential for the sustainable management of squid fisheries.