Studies on the promotion of glass eel survival rate and development of oral vaccines against bacterial diseases for juveniles of marbled eels (Anguilla marmorata)

• Main Authors: Hsu, Cheng-Chun, 徐程鈞
• Other Authors: 林正輝
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/15725478272221608939

碩士 === 國立臺灣海洋大學 === 水產養殖學系 === 103 === The present study investigated culture techniques and bacterial diseases control for juvenile marbled eels (Anguilla marmorata), the promotion for survival rate of glass eels also investigated. To develop oral divalent vaccine for marbled eel, two common bacterial pathogens, Edwardsiella tarda and Aeromonas hydrophila of the animal were used. To improve survival rates of glass eels, immunostimulants were fed to enhance non-specific immunity. The divalent vaccines encapsulated with agar, sodium alginate or CAP (Cellulose acetate phthalate) were prepared and oral feeding for the elvers was also conduced. The survival rate of glass eels (500/kg) were 72、75、82 and 63% fed With LZ8-S, sodium alginate, β-1,6-glucan and control, for 2 weeks, respectively after challenge with bacteria. The results revealed that immunostimulants could enhance immunity for glass eels leading to a better survival rate. To find an optimal salinity, glass eels were acclimatized to various salinity (10‰、5‰、3‰、0‰) and raised from glass eel stage (10000/kg) to elver stage (1000/kg). Higher survival rates of glass eels were obtained at weeks 4 raising in 5‰ and 10‰ salinity with survival rates of 84% and 80%, respectively. Lower survival rates were obtained at weeks 4 raising in 0‰ and 3‰ salinity with survival rates of 38% and 68%, respectively. Formalinized bacterial cells of A. hydrophila and E. tarda were encapsulated with agar, sodium alginate or cellulose acetate phthalate (CAP), separately, and used as oral vaccines to immunize glass eel (about 2g each). The relative percentage survival (RPS) of groups orally immunized with Et oral vaccine encapsulated with agar, sodium alginate and CAP was 70, 90, and 80%, respectively, after challenging with E. tarda. In addition, the RPS of groups orally immunized with Ah oral vaccine encapsulated with agar, sodium alginate and CAP was 70, 80, and 80%, respectively, after challenging with A.hydrophila. It reveals that the group fed with formalinized bacterial cells encapsulated with CAP exhibited best RPS higher than 80%. The highest antibody titlers of the eels orally immunized with the oral vaccine were all detected at week 12 after vaccination. In conclusion, the optimal salinities for rasing glass eel to elver stage and elver to yellow eel stage were 5-10‰ and 3-5‰, respectively. The immunostimulants used in this study exhibited enhancement of fish immunity. Good immunoprotection results for juvenile eels against A. hydrophila and E. tarda were obtained after orally immunized with formalinized bacterial cells of the two pathogens encapsulated with agar, sodium alginate or CAP. Further field study results may be useful for eel aquaculture in the future.