Ocean observations were conducted along 130°E on the way to Koror (Republic of Palau) during Koyo-maru 77th cruise on October 2018. During the cruise, the North Equatorial Current (NEC) was observed with geostrophic volume transport exceeding 70 Sv (1Sv＝10^6m^3/s) above 1000 dbar between 8°N and 24°N. In particular, it was strong north of 18°N. We found that surface (<100m) high temperature (>25℃)/ low salinity (<34.5PSU) water existed not only at southern part but also at northern part of the 130°E line. Because we could not find cloud cluster associated with the Intertropical Convergence Zone around the northern part of 130°E, it is suggested that the surface high-temperature/low-salinity water was advected by the NEC. Thus, we suggest that change of the NEC should be monitored and discussed because the boundary of this low-salinity water is thought to be the landmark of the spawing ground of Japanese eel in the NEC region.
North Equatorial Current
surface low-salinity water
Japanese eel
Koyo-maru 77th cruise
Ocean circulation