Amphidromous life cycle of Eleotris fusca (Gobioidei: Eleotridae), a widespread species from the Indo-Pacific studied by otolith analyses
Eleotris fusca is a widespread amphidromous fish found in the Indo-Pacific area. Its life cycle is characterised by a marine pelagic larval phase allowing the species to disperse in the ocean and then to recruit to remote island rivers. In order to examine its migratory history and pelagic larval duration (PLD), otolith microchemical and microstructural analyses were undertaken on 100 specimens collected in the rivers of four areas: Mayotte, Reunion Island (Indian Ocean), Vanuatu and French Polynesia (Pacific Ocean). Variations of Sr:Ca ratios were observed along the otoliths using a femtosecond laser ablation-inductively coupled plasma spectrometer (fs-LA-ICP-MS). The variation of the Sr:Ca ratio allowed us to reconstruct fish migratory movements between sea water (high Sr:Ca) and freshwater (low Sr:Ca), and led us to assume that Eleotris fusca is an amphidromous species. Using microstructural analysis, we observed that the PLD depended on the sampling site. In the Pacific Ocean, the PLD is similar in Vanuatu (mean ± SD: 90 ± 19.2 days) and French Polynesia (96.2 ± 17.5 days) whereas a significant difference emerged in the Indian Ocean between Mayotte (63.3 ± 11 days) and Reunion Island (114.8 ± 21.8 days).