The effect of irradiance on the survival and growth of abalone postlarvae Haliotis fulgens fed with Navicula incerta

Survival and growth of Haliotis fulgens postlarvae (11d old) were evaluated at four different irradiance levels, 6, 24, 47 and 75 microeinsteins times m super(-2) times s super(-1) ( mu E). Experimental vessels comprised 11 containers supplied with seawater flow and aeration. Four replicates per treatment were considered. Postlarvae were fed Navicula incerta, a benthic diatom. Survival and growth were evaluated. Shells were counted to determine mortality. To estimate shell size, video recorded images were processed by digital analysis. The highest survival (89.4% after 28d) and growth (37.1 mu m times d super(-1)) were found at 6 mu E, whereas the lowest survival (3.5%) and growth (21.1 mu m times d super(-1)) occurred at 47 mu E. These results suggest that abalone postlarvae have better survival and growth in the low light intensities under the particular conditions used in the present study.