Fish otolith record reveals possible tropical-subtropical fish community in temperate Japan during the exceptionally warm Last Interglacial period

Glacial-interglacial cycles are characteristic of the large-scale reorganisation of global climate during the Quaternary. Therefore, records of warmer-than-present periods, such as the Marine Isotope Stage (MIS) 5e, draw particular interest as they may aid scientists to predict how marine ecosystems may change in the future. However, fish fossil records during such warming periods are less clear. Here, we aim to reconstruct local fish fauna during the MIS 5e by describing fossil otoliths from two localities in central Japan belonging to the Otsu Sand and Mud Member of the Yokosuka Formation. A total of 544 otoliths were analysed, revealing the presence of at least 35 taxa. The fish assemblages reflect a mixture of coastal to oceanic epi-mesopelagic species. In addition, the remarkable occurrences of two present-day tropical species and its species composition demonstrate a possible complex tropical to subtropical-like fish fauna in the higher latitude Palaeo-Tokyo Bay during the warmer-than-present last interglacial period.