2011 Volume 59 Issue 2 Pages 255-264
We investigated trends in the population density and shell length of the planktonic larva Ruditapes philippinarum in Ariake Bay, Japan. In 2004, larvae were abundant along the coast in October and November. The mode of shell length in October (180 to 189μm) indicated that the larvae had hatched out about 2 weeks previously. In contrast, in June 2005 the larvae were found mainly in the center of the bay and the shell length mode (140 to 149μm) indicated that 7 to 10 days had elapsed since the larvae had hatched. These distributions varied over different periods, and the larvae spread into areas where adults were absent, such as the central and inner parts of the bay. The temporal changes in the modes suggested that the adults spawned more than once in each season, or that the timing of spawning differed among populations within a season.
