Numerical simulation to resolve the issue of downstream migration of the Japanese eel

In 1991 an expedition of a Japanese research vessel discovered that the spa wning ground of the Japanese eel is located in the North Equatorial Current (NEC) in the Pacific Ocean. Several unanswered questions about the distrib ution of the eel and their larvae downstream of the NEC, however, remain an d are unlikely to be resolved by observations alone. Three such questions a re about (1) previous misdetermination of spawning ground, (2) the large la rval catch off the west coast of Taiwan, not off the east coast, and (3) th e low abundance of larvae in Korean coastal waters. It had been thought tha t the physiological behavior of adult and larval eels and their adaptation to different environments determined their distributions. However, we have demonstrated that these issues can be explained by the water circulation in the North Pacific.