서해안 바지락 양식장의 서식환경과 서식밀도의 변화

Changes in density of manila clam, Ruditapes philippinarum to environment, catch and recruitment were studied in a few stations (Seonjae, Seongam, Hwangdo and Padori) in the West coast area of Korea from January, 2007 to December, 2009. Water temperature, salinity, dissolved oxygen and pH in the study stations were 0.8 to 31.2℃, 22.1 to 33.7 psu, 5.0 to 12.0 mg/L and 7.39 to 8.99, respectively. The concentrations of dissolved inorganic nitrogen, phosphate and silicate were 0.016 to 1.281 mg/L, 0.004 to 0.093 mg/L and 0.016 to 1.617 mg/L, respectively. Chlorophyll-a ranged from 0.2 to 12.1 μg/L, respectively. Substrata were mainly composed of muddy sand and very poorly sorted in Padori, muddy sand and well sorted in Seonjae and Hwangdo, gravelly muddy sand and poorly sorted in Seongam. Density was high in Seonjae and Seongam, but low in Hwangdo and Padori. In clam culture station, in which spat was naturally produced without sowing seedlings, the living density was decreased by increasing of death and a catch of shellfish, and recruitment was changed. Also, Density affected condition factor and shape of clam. Condition factor was the highest in Hwangdo, in which temperature in the winter and chlorophyll-a were high, and was the lowest in Padori. In the shape of clam, the shape in Seongam was a elongated form, but in Padori was a stunted form.