Experienced water temperature, depth and vertical movements of marbled flounder Pseudopleuronectes yokohamae from summer to winter in Suo Nada, the Seto Inland Sea, Japan

Abstract

 We released 30 adult marbled flounder Pseudopleuronectes yokohamae attached with temperature-depth data loggers off Himeshima Island at Suo Nada in the Seto Inland Sea, on July 3, 2017. Two loggers recorded data from the release day until December-January. In September, the hottest month of the year, the most frequently experienced water temperature and depth for marbled flounder were 24-25℃ (53.9-57.6%) and 0-5 m (44.3-73.9%), respectively. The experienced water temperature reached 27℃, but the proportion of the experienced water temperature over 26℃ was low at 3.9-4.5% for the two marbled flounder. We also noted vertical movements of the marbled flounder based on depth data. When marbled flounder experienced marked changes in water temperature, water depth and distribution area, they continued to move vertically. The results suggested that marbled flounder can survive in a water temperature lower than 26℃ in natural sea water. Moreover, vertical movements may be related to migration.