Effect of Substrate Component on the Growth and Survival of Juvenile Sunray Surf Clam（Mactra chinensis Philippi）

Substrate is a critical environmental factor affecting the activity of bivalves. To examine the effect of the substrate component on the growth and survival of juvenile sunray surf clam（Mactra chinensis Philippi）, a series of short-term experiments were conducted using a variety of substrates with different ratios of sand to mud. The experimental group cultured without substrate showed poor survival, with all juveniles died after day 20. The juveniles cultured in mud without sand showed a lower survival rate（25.54% ± 0.40% on day 45） than those in other groups. The juveniles cultured in sand without mud, or the mixtures of sand and mud with a ratio of 1：1 and 2：1, respectively, exhibited modest survival at day 45. Maximal weight gain rate（WGR）, shell length growth rate（LGR）, and specific growth rate（SGR） were observed when the sand concentration was 61.97%, 77.69%, and 64.64%, respectively. As the fast growth and high survival were observed when the sand to mud ratio was 1：1（50% sand） and 2：1（67% sand）, a sand concentration of more than 50% is optimal. The optimal concentration of sand in the substrate for rearing juvenile sunray surf clams was 67% which resulted in the fastest growth and highest survival. These results can be used to developing a nursery/farming technique of improving the yield of sunray surf clams.