Studies On Single-seed Oyster Spat Production And Culture Techniques Of Crassostrea Sikamea

In this paper, a series of studies were carried out on larval rearing, single-seedoyster spat production and culture techniques of Kumamoto oyster (Crassostreasikamea). Investigation on production of single-seed oyster spat will provide thebasical information for culture and promotion of single-seed oysters of C. sikamea.The major results are as follows:1. Based on the artificial breeding techniques of the Pacific oyster (Crassostreagigas), broodstocks culture and larval rearing of C.sikamea were conducted. Spermand eggs were naturally spawned from male and female cultured broodstocksrespectively after15days’ rearing. The fertilized eggs incubated into D-shaped larvaeat26°C in sea water after17to18hours. The stage of larval rearing was after optimalselection of D-shaped larvae, and the density of larvae was under the control of one ortwo larva per milliliter sea water. Then C.sikamea larvae developed into the eyespotlarvae stage after17days.2. Three methods were used for single-seed oyster spat production of C. sikamea.(1) Removing from the attached substrates. Due to some limitations, polypropyleneflat-bar package bags, nylon rope, polyethylene meshes, plastic membrane and300-mesh bolting-cloth net were not suitable for the production of single-seed oyster.Polyethylene corrugated plate is an ideal substrate, with high removing and growingrate, by which we can obtain large amount of juveniles.(2) Using particles as attached substrate. The adhesive rate of eyespots larvae is below1%and routine management is inconvenient using sand as substrate. The adhesiverate of eyespots larvae is only2.73%using shell powder as attached substrate andwater-flow culture facilities are needed. Both of methods are not suitable for theproduction of single-seed oyster.(3) Handling with epinephrine (EPI). After handling with EPI, the distortion ratio of eyespot larva of Crassostrea sikamea was extremely low, peaking at40%. And thismethod is also not suitable.3. The study on growth characteristics of single-seed juvenile oysters of C.sikamea.Juveniles in the same size were reared for25days. There were no significantdifferences in the growth rate of C. sikamea (P>0.05) between the single-seed andsedentary juvenile oysters with the increasing shell height of1417μm and1389μm,respectively.Salinity had a certain impact on the growth and survival of juvenile oysters in C.sikamea. Brackish water was the most benefit condition for the growth of C. sikameajuveniles. The highest growth rate was shown at the salinity of15followed by10and20, while the growth of juveniles was lowest at salinity of30. The appropriate rangeof salinity for C.sikamea juveniles was15to30, however, the survival rate decreasedsignificantly when the salinity was below10(P <0.05).