Growth history and inshore migration of the tropical eel, Anguilla marmorata, in the Pacific

A comparative study of the otolith microstructure and microchemistry of Anguilla marmorata glass eels in the western North Pacific (Japan, Taiwan, the Philippines, Indonesia) determined the timing of metamorphosis and age at recruitment to freshwater habitats with a view to learning about the early life history and recruitment of this species of tropical anguillid eel, which has a wide range throughout much of the western Pacific and parts of the Indian Ocean. Three new samples (from Japan, Taiwan, Indonesia) were analyzed and statistically compared along with two other previously published samples that were analyzed using the same techniques. Ages at metamorphosis and recruitment, respectively, were 123 +/- 13.4 days (mean +/- SD) and 154 +/- 17.0 days in specimens from Japan, 116 +/- 14.6 days and 145 +/- 15.6 days in those from Taiwan, 120 +/- 13.0 days and 154 +/- 13.5 days in the Philippines stock and 132 +/- 9.7 days and 159 +/- 11.7 days, and 120 +/- 15.6 days and 152 +/- 15.2 days in the Indonesian stock. The average duration of the period of metamorphosis estimated from otolith microstructure was very similar (15-17 days) in the specimens from all locations. A close linear relationship was found between the ages at metamorphosis and recruitment at all locations, suggesting that individuals that metamorphosed earlier were recruited to freshwater habitats at a younger age. Back-calculated hatching dates ranged over about 6 months of the year, suggesting that this species may spawn throughout much of the year. It is hypothesized that specimens from all four sites are from the same spawning population originating in a spawning area in the North Equatorial Current of the western North Pacific.