EGG DISPERSAL IN A CARIBBEAN CORAL-REEF FISH, THALASSOMA-BIFASCIATUM .2. DISPERSAL OFF THE REEF PLATFORM

Pelagically-spawning coral reef fishes are hypothesized to select sites and times for spawning that result in eggs being rapidly transported away from reef areas. Experiments at an inshore reef were conducted to test this hypothesis, with the bluehead wrasse as the model species. Using dye and drogues, spawning events were simulated at spawning and nonspawning sites (2 each) and times (1300 and 0700, respectively) and water masses tracked for 24 h, the known time to hatching. Each experiment consisted of a pair of simultaneous releases from a spawning and nonspawning site. Experiments were run during two seasons: spring and fall. On average, transport away from the test reef was greater for releases made at nonspawning times; no differences in transport were observed between spawning and nonspawning sites. Patches from paired releases tended to merge by the end of the experiment. Significant seasonal effects occurred; in the spring, transport was greater and paired patches merged after only 5 h, whereas patches in the fall remained distinct up to 15 h.