CONDITION, REPRODUCTIVE ACTIVITY, AND GROSS BIOCHEMICAL COMPOSITION OF THE MANILA CLAM, TAPES PHILIPPINARUM IN NATURAL AND NEWLY CREATED SANDY HABITATS OF THE SOUTHERN COAST OF KOREA

摘要

Sand was added to the mudflat in a small bay on the southern coast of Korea in an attempt to create a new habitat for the Manila clam (Tapesphilippinarum) in the muddy intertidal zone. To evaluate whether the newly created sandy habitat was functionally similar to natural ones, seasonal variations in condition, reproductive activity, and biochemical composition of clams in created and natural conditions were compared from May 2000 to October 2001. Clams reared in the newly created and natural habitats had similar patterns and levels with respect to condition and tissue dry weight. Standardized animal condition and tissue dry weight of clams peaked in spring, when protein and carbohydrate reserves were at maximum levels, and declined progressively throughout the summer-autumn period to October, as a result of continuous spawning. Condition and tissue weight were quickly restored during the winter-spring period, concurrently with accumulation of protein and carbohydrate reserves. Similar biochemicalcompositions and reproductive cycles for the clam stocks in the two habitats are likely to be related to their similar environmental conditions, in particular food availability. Comparison of the isotopic signatures of T. philippinarum tissues and potential food resources suggested that food availability in the study area was mostly dependent on resuspension of microphytobenthos, along with seasonal dynamics of phytoplankton. These observations clearly show that newly created sandy habitats may providehabitat functions that enable Manila clams to have similar biological cycles to those in natural habitats.