Culture of the Ark Shell, Anadara broughtonii in Yoja Bay

여자만에서의 피조개 양성

A culture experiment of the ark shell, Anadara broughtonii, one of the edible clams, was carried out in Yoja Bay located at the south ern coast of Korea to find the state of growth and any problems which influence them. Seed shells at an average length of 2.5cm and a weight of 2.5g were planted on bottom mud with a density 20 to 40 shells per square meter on March 10 and 11, 1982. Shell length, shell height, shell breadth, meat weight (wet weight), and total weight for six months from August 1982 to February 1983 were measured to find their state of growth. At the same time, the survival rate was investigated during the whole culture period through December 1983 when they were harvested. Growth, on the whole, was fast when water temperature was high. For a year, an average shell length and total weight attained to 6.1 cm and 63.0g respectively and meat weight was gained to 19.5g. It showed that the state of growth was favourable. Shell shape became round from the oval ana meat weight increase was faster than shell growth as time goes by regardless of water temperature while both shells and total weight increased faster during high temperature. A month after seed shells were planted, about $30\%$ of them was dead and a high mortality, say $5\%\;to\;8\%$ per month, was kept till September. It dropped to around $2\%$ aften divers eliminated starfish, Asterias spp., in August. Thereafter, the rate maintained through December. In all, the final survival rate was about $10\%$ at the time of harvest in December 1983. It was caused mainly by starfish predation. Therefore, a best way for satisifactory culture is seemed to find a way to get rid of the starfish.

남해 서부해역에 위치한 여자만에서 바닥식으로 양성한 피조개, Anadara broughtonii에 관한 성장과 폐사에 관해 1982년 8월부터 6개월간 조사한 결과는 다음과 같다. 1. 종패의 각장이 $20{\sim}30mm$, 평균 25mm되는 것을 1982년 3월 $1m^2$당 평균 30개체를 양성장 바닥에 살포하였는데, 약 6개월 후에 각장은 평균 48.0mm로 성장하였으며 익년 2월에는 평균 60.6mm가 되었다. 2. 패각과 각부중량의 증가는 고수온기에 빨랐으며 시간이 지남에 따라 패각의 한쪽 형태는 타원형에서 원형으로 변하고 육질중량의 증가는 패각 성장의 증가 속도보다 빨랐다. 3. 성장은 순조로와 피조개의 양성장으로 적합하지만 폐사가 많았다. 종패 살포 1개월 후 약 $30\%$가 폐사하고 폐사는 계속되어 수확시에는 생잔율이 약 $10\%$에 지나지 않았다. 폐사의 주 원인은 해적생물인 불가사리(Asterias spp.) 때문이었다.