MEPS 216:253-264 (2001)  -  doi:10.3354/meps216253

ABSTRACT: Otolith microstructure and microchemistry of the tropical eels Anguilla celebesensis Kaup, A. marmorata Quoy & Gaimard and A. bicolor pacifica Schmidt were examined in glass eels collected at the mouth of the Poigar River, north Sulawesi Island, Indonesia, throughout 1997. Ages at metamorphosis and recruitment, respectively, were 84 to 95 d and 104 to 118 d in A. celebesensis, 114 to 158 d and 144 to 182 d in A. marmorata, and 129 to 171 d and 158 to 201 d in A. bicolor pacifica. No significant differences were found in mean ages among months within any one species, whereas significant differences were found among species. Hatching was estimated to occur throughout almost the entire year in A. celebesensis and A. marmorata compared with intermittently over about 6 mo in A. bicolor pacifica. Based on year-round recruitment of A. bicolor pacifica at the mouth of the Poigar River in an earlier study and age at recruitment being constant throughout the year, the spawning season of this species may also occur throughout the year. In all species examined, positive linear relationships were found between age at metamorphosis and age at recruitment, suggesting that early metamorphosing larvae were recruited to freshwater habitats at an early age. Year-round recruitment of tropical glass eels to the river mouth would necessarily follow year-round spawning and stable recruitment age. Such a recruitment mechanism differs from that of temperate eels, the latter having a limited spawning season followed by a limited period of recruitment.

KEY WORDS: Tropical Anguilla spp. · Glass eel · Otolith · Growth increments · Sr:Ca ratios · Metamorphosis · Larval dispersal · Oceanic migration