Effects of diet, stocking density, and environmental factors on growth, survival, and metamorphosis of Manila clam Ruditapes philippinarum larvae

A series of experiments was conducted to evaluate the effects of diet, stocking density, and environmental factors on growth, survival, and metamorphosis of Manila clam Ruditapes philippinarum larvae. These experiments examined the following factors: diet ( Isochrysis spp., Chlorella spp., and a mixture of Isochrysis spp. and Chlorella spp. [1:1 w/w]), stocking density (5, 10, 15, and 20 larvae ml − 1 ), light intensity (un-shaded, partially shaded, and fully shaded), water filtration (unfiltered and sand-filtered), water exchange (50% and 100% once every other day; 25%, 50%, and 100% once daily; 50% and 100% twice daily), and the use of substrate (with and without sand as the substrate). Results indicated that Chlorella spp. could replace 50% of Isochrysis spp. as a food source for the Manila clam larvae without affecting growth, survival, and metamorphosis. Larval growth decreased significantly with increasing stocking density. A density of 5–10 larvae ml − 1 appeared to be optimal for normal growth of Manila clam larvae. Neither diet nor stocking density used in the study had a significant effect on larval survival. Under partially shaded (light intensity = 1000–5000 lx) and fully shaded (light intensity