Metamorphosis and inshore migration of tropical eels Anguilla spp. in the Indo-Pacific

Abstract

In order to determine the early life history and recruitment mechanisms of tropical eels Anguilla spp. in the Indo-Pacific, the timing of metamorphosis and age at recruitment to freshwater habitats were established from otolith microstructure and microchemistry analyses of juveniles of Anguilla celebesensis, A. marinorata and A. bicolor bicolor. Otolith increment width markedly increased from the age of 124 ± 12.0 d (mean ± SD) in A. celebesensis, 120 ± 13.0 d in A. marinorata (Philippines), 120 ± 15.6 d in A. marmorata (Indonesia) and 139 ± 15.9 d in A. bicolor bicolor. The timing of these increases was coincident with drastic decreases in otolith Sr:Ca ratios in each species, indicating the onset of metamorphosis from leptocephalus to glass eel. The mean duration of metamorphosis was 17 to 18 d in each species. Age at recruitment (mean ± SD) was 157 ± 13.7 d in A. celebesensis, 154 ± 13.5 d in A. marmorata (Philippines), 152 ± 15.2 d in A. marmorata (Indonesia) and 177 ± 16.4 d in A. bicolor bicolor. In all species examined, close linear relationships were found between ages at metamorphosis and recruitment, suggesting that individuals which metamorphosed earlier were recruited to freshwater habitats at a younger age.