Growth and survival of blacklip pearl oyster larvae fed different densities of microalgae

This paper reports on an experiment to determine growth and survival of bla cklip pearl oyster, Pinctada margaritifera (L.), larvae fed a 1:1 mixture o f Isochrysis aff. galbana clone T-ISO and Pavlova salina at six different d ensities (1, 2, 5, 10, 20 and 30 x 10(3) cells ml(-1)). Larval growth and s urvival were assessed every four days over a 20-day period. Exponential and logistic regression models were fitted to the growth and survival response s, respectively. Overall growth of larvae fed greater than or equal to 5 x 10(3) cells ml(-1) was significantly greater (p < 0.01) than growth of larv ae reared at other algal densities. The optimal food ration for maximum lar val growth was 20 x 10(3) cells ml(-1), which resulted in larvae with anter o-posterior shell length of 230 mu m after 20 days. These larvae were signi ficantly larger (p < 0.05) than those in all other treatments at the end of the experiment. Survival of larvae fed 0, 1 and 2 x 10(3) cells ml(-1) was significantly lower than that of larvae in all other treatments at the end of 15 days (p < 0.01). Maximal survival (8%) over the 20 day period was sh own by larvae fed 10 x 10(3) cells ml(-1), while lower survival was shown b y larvae fed 2 x 10(3) cells ml(-1) (2%) and 1 x 10(3) cells ml(-1) (0%).