Selection of substrates for settlement and growth of the purple clam Saxidomus purpuratus in laboratory culture

Abstract

The purple clam (Saxidomus purpuratus) is a local species inhabiting relatively restricted areas around Korea, Japan, and China. S. purpuratus is found from intertidal to ca. 40 m depth of subtidal areas. In Korea, this species is one of the most important shellfish resources with high prices. Recently, the commercial yield from the traditional exploitation of natural fisheries by divers has been declining due to over-harvesting; much attention has been concentrated to the aquaculture of this species. Thanks to the cooperative efforts by the Korea Ocean Research & Development Institute (KORDI) and Taean Marine Hatchery of the National Fisheries Research & Development Institute (NFRDI), some of physical and biological conditions for artificial fertilization, embryonic development, and larval growth were appropriately established. However, the rearing conditions for post-settled spats have not been well understood yet. Here, we set the purpose of this study to determine the optimal substrates for settlement and growth of spats of S. purpuratus.Experiments were conducted for 4 months (2 months for settlement and 2 months for growth) with 3 different types of sediments (muddy, mixed, and sandy sediments) as substrates for settlement and growth of S. purpuratus. The number of settled spats in muddy sediments was more than 2 times higher than those in mixed or sandy sediments. But, the average size of settled spats in muddy sediments was smaller than those in mixed or sandy sediments. After 2 months of growth period, shell length increased more than 10 times (ca. 0.8 to 10.8 mm). Shell length was highest in mixed sediments, followed by muddy sediments; lowest in sandy sediments. But, the differences were not statistically significant. Growth rate decreased as shell length increased. When shell length was less than 2 mm, growth rate in mixed sediments was significantly higher than that in sandy sediments. When shell length was more than 2 mm, there was no significant dif