Insights on endemism: comparison of the duration of the marine larval phase estimated by otolith microstructural analysis of three amphidromous Sicyopterus species (Gobioidei: Sicydiinae) from Vanuatu and New Caledonia

The microstructure of otoliths of three amphidromous gobies (Sicydiinae) of the genus Sicyopterus has been analysed. One of these species, Sicyopterus lagocephalus has a widespread distribution whereas the other two are endemic (Sicyopterus aiensis, from Vanuatu and Sicyopterus sarasini, from New Caledonia). The microstructural analysis of the otoliths showed that the duration of the marine larval phase is significantly shorter for both endemic species than for the cosmopolitan species (131 +/- 3.4 days for S. lagocephalus, 79.2 +/- 4.6 days for S. aiensis and 76.5 +/- 3.9 days for S. sarasini). These results led us to infer that it could be one of the factors explaining endemism. We have also improved our knowledge on the processes undergone during the marine phase by studying the growth of the otolith. This work allowed us to propose possible migration routes. These species' reproduction period has also been studied by back-calculating hatching dates. All these elements improve our understanding of the life-history traits and dispersion strategies of these species, which is crucial to implementing conservation measures in order to protect them and their environment, both threatened by anthropogenic actions.