This study analyzed the flow inside floating seedling equipment for Scapharca subcrenata. Due to the aging society of fishing villages, it is impossible to continuously input the labor force. Therefore, it is necessary to improve efficiency. Scapharca subcrenata has high per capita consumption. It serves as an important aquatic food resource. Scapharca subcrenata culture tends to be highly dependent on the natural environment. Production of Scapharca subcrenata is difficult to predict with low stability. In the past, manpower directly installed bamboo nets in mudflats. The seedling equipment devised in this study is a floating type and can be freely moved on the sea according to the prediction of Scapharca subcrenata generation. The flow around the floating seedling equipment was analyzed by numerical analysis. The physical phenomena of the flow around the net inside the floating seedling equipment were visualized. As a result, the space between the floating seedling equipment and the bottom net and the space between the net groups showed a lower flow rate than the inlet flow rate. It is expected that the low flow rate of the floating seedling equipment will have a positive effect on the attachment of Scapharca subcrenata.

Seafood is attracting attention as a future food industry. In recent years, the demand for fishery equipment of mechanization, automation, and unmanned was increased due to the environment affected by seafood processing, stricter regulations on safety, decline and aging of fishery worker. Ark shell (Scapharca subcrenata) was being produced in many steps in the production process. The process has been made such as collection–landing–washing–first sort (goods/non-goods)–transports– second sort (size). It was undergone first and second steps by delivering to the consumer. Here, the first step is to sort goods to collection and the second step is to sort by size. The fishery workers need ten people in first step and six people in second step. The workload of one hour per kg is 4,247 kg/h in first step and 2,213 kg/h in second step. In addition, the goods ratio by work process was 79% in first step and 98% in the second step. In this process, a lot of fishery worker and working time is needed. Therefore, this study developed elemental techniques for an automated size sorting system considering the working process problem, time and situation for washing and sorting of ark shell.

Ultrastructural studies on oocyte development and vitellogenesis in oocytes, and the functions of follicle cells during oogenesis and oocyte degeneration were investigated to clarifyb the reproductive mechanism on vitellogenesis of Scapharca subcrenata using electron microscope observations. In this study, vitellogenesis during oogenesis in the oocytes occured by way of autosynthesis and heterosynthesis. Of two processes of vitellogenesis during oogenesis, the process of endogenous autosynthesis involved the combined activity of the Golgi complex, mitochondria and rough endoplasmic reticulum. However, the process of exogenous heterosynthesis involved endocytotic incorporation of extraovarian precursors at the basal region of the oolema of the early vitellogenic oocytes before the formation of the vitelline coat. In this study, follicle cells, which attached to the previtellogenic and vitellogenic oocytes, were easily found. In particular, the follicle cells were involved in the development of previtellogenic oocytes by the supply of nutrients, and vitellogenesis in the early and late vitellogenic oocytes by endocytosis of yolk precursors. Based on observations of follicle cells attached to degenerating oocytes after spawning, follicles of this species are involved in lysosomal induction of oocyte degeneration for the resorption phagosomes (phagolysosomes) in the cytoplasm for nutrient storage, as seen in other bivalves. In this study, the functions of follicle cells can accumulate reserves of lipid granules and glycogen particles for vitellogenesis from degenerating oocytes after spawning.

국내 유용 양식품종인 새꼬막, Scapharca subcrenata은 돌조개 목 (Order Arcoida) 돌조개 과 (Family Arcidae)에 속하는 종으로써, 같은 과에 속하는 꼬막, Tegillarca granosa과 피조개, Scapharca broughtonii의 중간크기이다 (Kwon et al., 2001). 새꼬막이 국내 연 총생산량은 많게는 3,000 톤 가까이 되지만, 종패의 수급에 있어 주로 자연채묘에 의존하고 있기 때문에 지속적이고 양호한 채묘율을 기대할 수 있다. 새꼬막에 관련된 연구는 수온과 염분 등 환경요인에 의한 영향 (Nakamura, 2005; Shi et al., 2007; Fang et al., 2008), 생식주기 (Kim et al., 2008), 유생분포 (Kim et al., 2006), 채묘와 성장 (Lim and Hur, 2010) 등 그 보고되고 있지만, 꼬막에 비해 많지 않으며, 특히 국내의 경우 인공성숙 등에 관한 연구는 찾아보기 힘들다. 따라서 본 연구는 새꼬막의 성패를 이용하여 성 성숙에 있어 가장 중요한 요인 중 하나인 수온 상승만으로도 생식소의 발달 및 정상적인 난 발생이 진행되는지 파악하고자 하였다. 연구에 사용된 새꼬막의 크기는 각장 31.81±2.21 ㎜, 전중 9.87±1.94 g이었으며, 전라남도 고흥군의 여자만에서 채집하였다. 사육기간은 28일 간이었으며, 대조구는 일반수온으로 설정하였고, 가온구는 매일 0.5℃씩 수온을 상승시킨 후 20℃가 되는 시점에서 일주일간 수온을 유지하였다. 먹이는 Isochrysis galbana, Chactoceros calcitrans, Tetraselmis tetrathele 3종의 미세조류를 혼합하여 1 ton 수조에 3시간마다 200ℓ (5,000～6,000 cells/㎖)씩 자동급이장치에 의해 공급하였다. 매일 사망개체를 파악하여 생존율을 조사하였으며, 7일 간격으로 채집하여 성비, 생식소발달 및 생식소지수를 분석하였다. 또한, 가온성숙된 개체들을 대상으로 간출자극에 의한 산란유발을 실시한 후 정상적인 난발생이 이루어지는지 관찰하였다. 연구 종료 후 관찰된 새꼬막의 생존율은 대조구에 비해 낮은 생존율을 보이고 있었다. 성비는 암:수의 비가 대조구는 1:0.97로 별다른 차이를 보이지 않았지만, 가온구는 1:0.62로 암컷이 높게 나타났다. 비만도는 대조구와 가온구가 유의한 차이를 보이는 가운데 수온 17℃ 이상부터 증가폭이 높게 나타났다. 생식소발달빈도는 암․수 모두 대조구의 경우 발달이 느렸으며, 가온구는 수온 20℃인 사육 21일부터 28일 사이에 성숙기에 도달한 개체들이 80% 이상 관찰되었다. 생식소지수는 대조구에 비해 수온이 높을수록 증가하는 경향을 보였다. 수온 26℃ (32‰)에서 새꼬막의 수정란 크기는 직경 63.17±1.22 ㎛였으며, 수정률은 82.17±3.55%였다. 부화율은 63.57±2.36%였다. D형 유생의 발생소요시간은 수정 후 약 15시간으로 나타났으며, 크기는 각장 82.85±0.87 ㎛, 각고 72.65±1.07 ㎛였다.