Study on Spawning Induction and Larvae Breeding of the Hard Clam, Meretrix petechiails (Lamarck)

For industrialization of the hard clams, Meretrix petechiails (Lamarck), spawning was induced per spawning induction technique in the artificial maturation group administered of parent maturation control and the natural maturation group of which parents were transported for artificial spawning per time period. Then, fertilization rates, hatching rates and D-shaped larva development rates were investigated. In addition, growth and survival rates of larvae were investigated per larva breeding technique. The results of spawning induction by exposure in the artificial maturation group indicated that response rates were relatively higher at 23% and 32% respectively at the 4th hour and the 8th hour of exposure. In terms of water temperature increase, responses began only when the temperature reached $28^{\circ}C$ or higher. In the experiment group administered with both exposure and water temperature increase techniques, response rate was found to be 45% or higher at the 4th hour of exposure and the temperature of $28^{\circ}C$. At the temperatures of 29, 30 and $31^{\circ}C$, significant differences were not observed. Therefore, it was indicated that the response rates of parent hard clams were higher toward water temperature increase than exposure time. As for spawning induction per time period of the transported parent group, response rate and D-shaped larva development rate were the highest at 67.6% and 96% respectively on August 6, 2009. In terms of water temperatures during larva breeding experiment, growth was faster as water temperature was higher. In addition, growth and survival rates were relatively higher at the salinity of 25. In terms of stocking density, growth and survival rates were relatively higher at 5 inds./mL.

말백합, Meretrix petechiails (Lamarck) 의 산란유발 및 유생사육에 관한 연구

본 연구는 말백합 산업화를 위하여 어미성숙 관리한 인위성숙개체군과 시기별로 어미를 수송 채란한 자연성숙개체군을 산란유발 방법 별로 산란을 유도하여, 수정율, 부화율, D형 유생 발생률을 조사하였고, 유생사육 방법별로 유생의 성장과 생존율 등을 조사하였다. 인위성숙개체군의 간출시간별로 산란 유도한 결과 간출 4시간 및 8시간이 반응률이 23% 및 32%로 비교적 높았고, 수온 상승별로는 $28^{\circ}C$ 이상 되어야 반응이 시작되었다. 간출 및 수온상승 병행 시험구에서는 간출 4시간 및 $28^{\circ}C$에서 반응률이 45% 이상으로 나타났고, 29, 30, $31^{\circ}C$에서는 유의한 차이를 보이지 않아 말백합 어미는 간출시간보다는 수온상승에 반응률이 높은 것으로 나타났다. 어미수송개체군의 시기별 산란유발 결과는 2009년 8월 6일이 반응률 67.6%, D형 유생 발생률이 96%로 가장 높게 나타났다. 유생사육 시험 중 수온별로는 유생의 성장과 생존율을 고려할 때 유생사육 적정수온은 $27-31^{\circ}C$, 최적수온은 $29^{\circ}C$로 나타났고, 염분은 25에서 성장 및 생존율이 비교적 높았으며, 수용밀도별로는 5 inds./mL에서 성장 및 생존율이 비교적 높게 나타났음을 알 수 있었다.