Effects of NEC Transport and Bifurcation Latitude on Japanese Eel Larval Migration

Numerical lagrangian experiments were conducted to study the effects of current strength and position on Japanese eel larval migration in the western North Pacific. Particles were released from the grid points that cover Japanese eel spawning area and from different depths during the spawning seasons of 19 years (1991-2009) and the percentages of particles that reach the coastal areas of Taiwan and Japan were calculated at the end of one-year simulation. The percentages of particles that reach Japan are related to, but lower than, those that reach Taiwan. More Particles reach Taiwan when the transport of the North Equatorial Current (NEC) is stronger and when NEC bifurcates at more southern latitudes, because the particles are able to travel through NEC and to enter the Kuroshio more quickly. When the NEC transport is strong, high percentages of particles that reach Taiwan come from the northern part of the spawning area, while when the transport is weak, they come more evenly from the entire spawning area. Since the NEC transport and bifurcation latitude are controlled by wind forcing in the tropical western Pacific, the interannual and decadal variability of successful Japanese eel larval migration are thus related to the climate variability.