Reproduction and marine life history of an endemic amphidromous gobiid fish of Reunion Island

Abstract

Among amphidromous species, life-history traits of pelagic larvae show high vari- ability between and within species and populations, due to the spatial and temporal variability of the marine environment. Temperature, food availability and seasonal conditions affect survival and larval growth. Among species with an extensive reproduction period, the pelagic conditions encountered by larvae vary according to the hatching date and induce variability in the post- larval and recruitment traits. Post-larvae of the amphidromous goby Cotylopus acutipinnis were collected every new moon between February 2008 and December 2009 at the mouth of a river on Reunion (Mascarene Archipelago, SW Indian Ocean). The relationship between pelagic larval duration (PLD), growth and marine temperature conditions was analysed using the chronological properties of otoliths. C. acutipinnis PLD (mean ± CI: 108.2 ± 1.2 d; range: 66 to 164 d) and size-at- recruitment (mean ± CI: 20.5 ± 0.1 mm; range: 17 to 23 mm) varied widely depending on the time of year. Back-calculation of hatching dates showed an extensive spawning season between November and July, which included 2 spawning peaks during the early austral summer and early winter. Summer spawning and high seawater temperature induced faster growth, shorter PLDs and smaller size-at-recruitment compared to early winter reproduction. The significant morpho- logical changes that were demonstrated among amphidromous recruits might influence post- recruitment survival and juvenile settlement in freshwater. Selective mortality may occur accord- ing to early life-history traits such as growth patterns, size-at-recruitment and post-larval condition, and should be considered in population management.