2020 年 37 巻 2 号 p. 25-29
The ascidian Styela plicata (Lesueur, 1823), which to date has been recorded from mid-temperate to tropical waters along the Japanese Pacific coast, from mid- and warm-temperate waters along the Sea of Japan coast, with northern limits in Tokyo Bay and Mutsu Bay, respectively, and from the mid-temperate Seto Inland Sea, was collected for the first time in 2019 from cool-temperate Ofunato Bay, Iwate Prefecture, further north of Tokyo Bay on the Pacific coast. Furthermore, hearsay evidence indicates that the ascidian has been observed on aquaculture equipment in Ofunato Bay since summer of 2017, following the 2016 introduction of the oyster Crassostrea nippona to the bay from Akita Prefecture for aquaculture. Long-term viability of the Ofunato Bay population of S. plicata now appears likely, indicating tolerance to winter water temperatures (to ca. 6°C), and a potential threat to local aquaculture.
