Recruitment and movement of the hard clam Meretrix lusoria in a tidal river of northern Kyushu, Japan

摘要

Size-frequency distributions of Meretrix lusoria, a commercially important bivalve in Japan, were compared among 6 sites in tidal flats of a small river in Kafuri Bay, northern Kyushu, Japan during 2006-2008. In Kafuri Bay, the hard clam resource is strictly managed and mean biomass of this species on the fishing ground (about 1.5 km(2)) exceeded 1.5 kg m(-2) in 2008. Small clams ( 40 mm SL) were rare there. In contrast, in the lower site of the marine area (site L), most clams were > 30 mm SL. These results indicate that small clams move from riverine to marine areas with growth (post-settlement movement). Year-round, very small clams ( 5 mm SL in a short period of time