First capture of post-spawning female of the Japanese eel Anguilla japonica at the southern West Mariana Ridge

Two adult male freshwater eels, Anguilla japonica, were captured in June 2008 in the West Mariana Ridge (13A degrees N, 142A degrees E) in the North Pacific, but collections of females have yet to be reported. In September 2008, we successfully caught two adult female A. japonica, 55.5 and 66.2 cm in total length, in the adjacent but northern area (14A degrees N, 143A degrees E). Six newly hatched eel larvae (pre-leptocephali) were also collected by subsequent plankton sampling conducted near the female catch area. Female adults appeared to be in the post-spawning state, probably a considerable time after spawning, since a small number of remarkably regressed oocytes (50-250 mu m in diameter) were observed in the ovaries. Capture of post-spawning female eels and newly hatched larvae near the Suruga Seamount (14A degrees N) together with the previous collection of mature males in the southern area (13A degrees N) corroborates that the area along the West Mariana Ridge is the spawning area of this species, but suggests that the eel spawning may occur over a wider area than previously expected.