BROODSTOCK CONDITIONING, SPAWNING INDUCTION, AND EARLY LARVAL DEVELOPMENT OF THE TROPICAL ROCK OYSTER STRIOSTREA PRISMATICA (GRAY 1825)

The tropical rock oyster Striostrea prismatica is a commercially valuable bivalve mollusc found along the Pacific tropical coast. A laboratory study was conducted to investigate broodstock acclimation at two temperatures (28.3 +/- 0.9 degrees C and 22.2 +/- 0.9 degrees C) fed a combined microalgae diet (Chaetoceros gracilis and Isochrysis galbana at 150 cells/mu L/day and 100 cells/mu L/day, respectively) for 7 wk, and to investigate seven treatments to stimulate spawning of individuals acclimated at both temperatures. Treatments to induce spawning consisted of a 10 degrees C temperature decrease for 60 min (HS1), a temperature increase to 30 degrees C for 30 min (HS2), a 5 degrees C temperature increase for 60 min followed by 30 min of desiccation (HSD), a decrease in salinity to 15 psu for 30 min (SS1), an increase in salinity to 96 psu for 30 min (SS2), overfeeding with C. gracilis microalgae (OF), and the addition of oyster sperm (SPM). All treatments were treated with oyster sperm after 1 h of the last stimulus. Spawning success was evaluated by measuring egg production, fertilization percentage, and response time of spawning. Only broodstock held at 28 degrees C spawned (51.8%). All organisms in the HSD treatment spawned after 1.40 +/- 1.01 h. Oocytes released per individual and fertilization rate averaged 34.88 +/- 23.81 x 10(6) and 89.82 +/- 5.90%, respectively. Addition of sperm enhanced spawning success in the HS1, HS2, and SS1 treatments.