Larval Settlement and Spat Growth of the Tropical Oyster Crassostrea belcheri (Sowerby 1871) in Response to Substrate Preparations

Substrate preparation is a key factor for the settlement and metamorphosis of oyster larvae. In thepresent study, the effects of substrate preparations on larval settlement and growth of spat of the tropical oyster, Crassostrea belcheri were evaluated in two trials in a semi-closed recirculation system. In each trial, substrates were prepared by three different methods, including immersion in seawater for 2 hr, conditioning with a biofilm, and presoaking in adult tissue extracts. The number of larvae that settled on substrate presoaked in adult tissue extracts or which had a biofilm were significantly higher (P 0.05) than the number that settled on substrates immersed in seawater for 2 hr in both trials. Mean settlement rates were 30.53±2.91, 38.52±2.81 and 40.86±3.65% in trial 1, and 19.02±2.49, 28.66±3.13 and 34.13±2.91% in trial 2 for substrates prepared by immersion in seawater for 2 hr, with a biofilm, and presoaked in tissue extracts, respectively. Differences in the increments of shell width and length among oyster spat nursed over 4 weeks were non-significant (P 0.05) among the treatments.