Larval recruitment of the manila clam Ruditapes philippinarum in Ariake Sound, southern Japan
R. Ishii, H. Sekiguchi, Y. Nakahara, Y. Jinnai-2001
Fisheries Science, 67(4): 579-591
(from Current Contents)
Abstract :
The mechanisms by which catch yields of the manila
clam Ruditapes philippinarum have decreased drastically in Kumamoto
Prefecture, southern Japan, and the larval recruitment by which benthic
populations of the clam are maintained were studied. Samples at different
growth stages (planktonic larvae, new settlers, and small to large bivalves
of the species) were collected from February 1997 to December 1998 on two
tidal flats (Kawaguchi and Nameishi, 20 km distance from each other) along
the eastern coast of Ariake Sound. Densities of planktonic larvae, new
settlers and small bivalves were generally higher at Kawaguchi than
Nameishi. The higher density of large bivalves at Kawaguchi depends on a
high larval density. Larval retention mechanisms coupled with water movement
at Kawaguchi, such as tidal residual currents, may be related intimately
with the higher larval density at Kawaguchi. Predation by shore birds at and
after recruitment may be related to the lower density of large bivalves
recorded at Kawaguchi in 1998, despite larval densities being higher there.