[M-ZZ42] Process, Environment, and Exploration of Marine Manganese Deposits

[MZZ42-05] Assessment of seamount and coastal connectivity using the deep-sea eel (Simenchelys parasitica: Synaphobranchidae)

*Akinori Teramura¹, Naoki Saito¹, Hiroki Kise¹, Miyuki Nishijima¹, Shunsuke Kondo², Tomo Kitahashi², Yuya Yamamoto², Atsushi Suzuki¹, Akira Iguchi¹ (1.National Institute of Advanced Industrial Science and Technology, 2.KANSO TECHNOS CO., LTD.)

Keywords:MIG-seq, Cobalt rich crust, genetic diversity, deep-sea fish

In environmental impact assessment for the development of deep-sea marine mineral resources, which are currently the focus of much attention, a preliminary assessment of biodiversity and the connectivity that contributes to its maintenance and formation is important to minimize the potential losses from development. These species connectivity studies should use a variety of species, such as plankton, benthos, and nekton, to assess connectivity. However, few assessments of seamount and coastal connectivity have been carried out for nekton, which can move freely over large areas, such as fish. We therefore investigated the Takuyo-Daigo Seamount and coastal connectivity, where the first Cobalt rich crust mining test was conducted in July 2020 using fish genome-wide analysis. Our target species, the snubnosed eel (Simenchelys parasitica Gill, 1879), is a highly carrion-eating species, so simple bait traps can be used to collect large numbers of individuals. A total of 122 of these were collected from the Okinawa Trough, the Suruga Bay, the Bayonnaise Knoll, and the Takuyo-Daigo Seamount, and 7199 SNPs were obtained by MIG-seq. Population structure analysis based on this SNP data showed that, surprisingly, no genetic differentiation occurred between the four oceanic regions, and the 0 Fst value in the Okinawa Trough to Takuyo-Daigo Seamount, which is the farthest linear distance away, indicating that they are the same population. Therefore, the detection of individual migration rates between the different areas indicated that the snubnosed eel may be undergoing a strong directional migration from Suruga Bay to the Bayonnaise Knoll at the four sites examined in this study. This is consistent with the results of ocean current simulations, which showed a strong directional surface current from the Suruga Bay to the Bayonnaise Knoll. This suggests that widely distributed species such as the snubnosed eel are likely to be assisted in their directional wide migration and emigration by surface currents. In other words, the snubnosed eel in the waters around the Japanese archipelago has strong connectivity to offshore seamounts such as the Takuyo-Daigo Seamount.