REPLENISHMENT OF FISH POPULATIONS IN THE ENCLOSED LAGOON OF TAIARO ATOLL - (TUAMOTU ARCHIPELAGO, FRENCH-POLYNESIA) EVIDENCE FROM EGGS AND LARVAE

Taiaro Atoll Lagoon is normally isolated from the ocean, but at least 125 marine fish species of 31 families are present there. We sampled f ish larvae in Taiaro Lagoon and the nearby ocean in February 1994 with plankton net, neuston net and light trap to investigate which taxa we re completing their life cycles in the lagoon. Concentrations of fish eggs and larvae were very high in the lagoon indicating intense spawni ng, but larvae of only 18 taxa of 10 families were present. Only six, a callionymid, gobiids, a hemiramphid, a microdesmid, and two pomacent rids, were present across a full range of pelagic sizes, and were clea rly completing their pelagic stage in the lagoon. Four other taxa, an apogonid, two labrids and a scarid, were common, but the largest indiv iduals were small (< 5 mm) postflexion larvae. These may have been com pleting their pelagic stage in the lagoon. The remaining lagoonal larv ae (eight taxa) were rare and at the preflexion stage, so we could onl y conclude that they hatched from eggs spawned in the lagoon. Nineteen taxa of 15 families found as adults in the lagoon were present outsid e the lagoon as larvae, but not inside, suggesting that they may not n ormally complete their life cycles in the lagoon. Horizontal distribut ions of larvae-in the lagoon are apparently due to the interaction of larval vertical distribution behaviour with a wind-driven countercurre nt system.