Spatial Distributions of Larval, Newly-Settled, and Benthic Stages of Bivalves in Subtidal Areas Adjacent to Tidal Flats

Abstract

Spatial distributions of planktonic larvae and newly-settled and benthic stages of three species of bivalves (Ruditapes philippinarum, Nuttallia oliuacea, Musculista senhousia) were investigated in the subtidal area adjacent to the tidal flats of the Ano and Shitomo Rivers. In all three species the benthic juveniles and adults were very scarce in the subtidal area, while the larvae occurred abundantly there. The newly-settled and benthic bivalves tended to occur at sites near the low water of tidal level water. This suggests that larvae avoid settling on the bottom in the subtidal area but are transported to the lower margin of the tidal flats.