Early life history of tropical Anguilla leptocephali in the western Pacific Ocean

In order to examine the early life-history characteristics of tropical eels , otolith microstructure and microchemistry were examined in leptocephali o f Anguilla bicolor pacifica (27.6-54.1 mm TL, n = 20) and A. marmorata (22. 0-47.3 mm TL, n = 8) collected during a cruise in the western Pacific. A. b icolor pacifica occurred between 10 degreesN and 15 degreesN in the west an d between 5 degreesS and 10 degreesN farther to the east. A. marmorata also occurred in two different latitudinal ranges in the Northern (15-16 degree sN) and Southern Hemispheres (3-15 degreesS) of the western Pacific. The in crement widths in the otoliths of these leptocephali increased between the hatch check (0 days) and about an age of 30 days in both species, and then gradually decreased toward the otolith edge. Otolith Sr:Ca ratios showed a gradual increase from the otolith center to the edge. The ages of A. bicolo r pacifica and A. marmorta leptocephali ranged from 40 to 128 days and from 38 to 99 days, respectively. Growth rates of A. bicolor pacifica and A. ma rmorata leptocephali ranged from 0.33 to 0.71 mm day(-1) and from 0.45 to 0 .63 mm day(-1) respectively. These leptocephali had estimated growth rates that were spread out throughout most of the reported range of growth rates of the leptocephali of the temperate species, the Japanese eel and the Atla ntic eels. Differences in the spatial distribution in relation to current s ystems, and the age and size compositions of the leptocephali of A. bicolor pacifica and A. marmorata suggested different spawning locations for these two species.