協助巴拉圭建立條紋鴨嘴鯰人工繁殖技術之研究

Study of assisting Paraguay to establish artificial breeding technology for barred sorubim (Pseudoplatystoma fasciatum)

本研究之鴨嘴鯰種魚主要係捕獲自南美洲巴拉圭河，捕撈漁法以短時間流刺網對種魚的傷害最輕，活存率較高。另，由民間養殖場採購巴西雜交鯰進行繁殖試驗。本研究計採集75尾野生種魚，其中只有4尾於捕獲時確認卵巢卵粒偏核率超過30%，經1次催產注射即可採卵，且受精率平均高達72.5%。另，攜回中心培育之種魚中只有3尾之卵粒偏核率超過20%，經施打2次催產針劑，結果僅有2尾成功產卵並孵育出魚苗，惟受精率僅10~15%。鴨嘴鯰受精卵為黏性，會黏附於孵化桶壁上，水溫在24~28℃約20小時可全數孵化。孵化後第3天開始攝餌，開口先以豐年蝦孵化幼苗餵食，其後分別以橈腳類、小型枝腳類、大型枝腳類或絞碎之牛心肉餵食，三週後即可開始進行人工飼料馴餌。本研究共有7次成功孵化純種或雜交種魚苗，結果發現各種魚苗孵化所需時間差異不大，惟雜交子代較容易發生畸形的魚苗，在培育上雜交魚苗則較易適應人工飼料，成長體型參差度亦較小，且平均活存率也較高。

The breeder of barred sorubim (Pseudoplatystoma fasciatum) in this study mostly caught from the Paraguay River of South America. According to different fishing methods, “Drift Gillnet” caused the least damage to fish, and got a higher survival rate. Moreover, this study also purchased the hybrid barred sorubim from Brazil which was nurtured by the local farmer for breeding experiments. A total 75 wild fish was collected in this study, only 4 of them were confirmed that the migratory nucleus rate of the oocytes exceeded 30% at the time of captured. The eggs can be collected after one injection, and the average fertilization rate is 72.5%. After all the breeders were nurtured in the center, 3 of them had over 20% of the migratory nucleus rate of the oocytes, only 2 spawned successfully and hatched fry after 2 times of injections, and the fertilization rate was 10-15%. The eggs of barred sorubim had an adhesive layer, they can easily stick to the wall of the incubator, and can be fully hatched for about 20 hours of 24~28℃ water temperature. The fry was initially fed in the third day after hatching, started feeding with the hatched artemia first, and then fed with copepods, small cladocera, large cladocera or minced bovine heart. Artificial feed may be replaced meat or large cladocera after three weeks. A total of 7 times successful incubation experiments of pure or hybrid fry in this study. It was observed that there is no difference in hatching time of various fry. However, the hybrid offspring was found more deformity fingerling, but is easier to accept the artificial feed during nurturing. The hybrid fry had more uniform size of the body length, and also had a higher average survival rate.