Reproductive Cycle and First Sexual Maturity of Sinonovacula constricta (Lamarck, 1818) (Bivalvia: Pharidae) in Western Korea
Tae-Hoo Kim and Ki-Young Lee
School of Marine Life Science, Kunsan National University, Gunsan 573-701, Korea
The gonad index, reproductive cycle and first sexual maturity of Sinonovacula constricta collected from Simpo, Kimje-gun, Korea were investigated by histological analysis. The gonad index (GI) in both sexes of S. constricta increased from April and reached a maximum in July when the water temperature rapidly increased. And then, the GI values gradually decreased by spawning from August through October. Monthly variations in the GI showed a close relationship with ovarian development. The reproductive cycle in females and males can be classified into five successive stages: early active stage (March to June), late active stage (May to July), ripe stage (July to September), partially spawned stage (August to October), spent/inactive stage (October to March). The percentage of first sexual maturations in female and male clams of 50.1-60.0 mm in shell length was over 50%, and for clams over 70.1 mm in shell length, it was 100%. Because harvesting clams < 50.1 mm in shell length could potentially cause a drastic reduction in recruitment, a measure including a prohibitory fishing size should be taken for adequate improved fisheries resource management.
  
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