農業部-水產試驗所全球資訊網農業部-水產試驗所全球資訊網

供催熟試驗用的魚塭培育之雌性日本鰻之平均全長83.2 ±6.3 (67.5-103.5) cm，平均體重1072±191 (623-1700) g，合計共210尾。將催熟中的雌鰻之成熟度，依胸鰭的黑色化程度分為6級 (0-5級)，在第一個月，依據雌鰻胸鰭黑色化的程度，每間隔2週，以劑量0.5-1.0 IU/g BW的人類絨毛膜促性腺激素 (Human Chorionic Gonadotropin，HCG) 注射，使其在1個月後，達成熟度3-4級，即利用注射HCG劑量的不同，儘量促使成熟度的同步化，第4週起，體重800 g以上的雌鰻，每尾每週注射4 粒塘虱魚腦下腺的研磨液，體重800 g以下者注射3粒。催熟的後期，配合縮短注射間隔及降低注射劑量，在注射激素後約2 個月起，雌鰻可陸續達到最後成熟階段，此時以劑量2 μg/g BW的排卵素 (17α\, 20β-dihydroxy-4-pregnen-3-one，DHP) 注射誘發其排卵。雌鰻注射排卵素後，以3-5尾雄鰻與之配對。雌鰻會在100 l的小水族箱中自行產卵，無自行產卵者，輔以人工擠卵、授精的方式，也可達到全年均能生產受精卵的目標。HCG可明顯地促進鰻魚婚姻色的表現，假若再配合注射腦下腺研磨液，可產生催熟的加成效果，因而可縮短催熟時程。迄至目前魚塭培育的雌鰻，經催熟後，僅有44.8 %達到最後成熟的階段，而其中約有70 %在催熟後2-4個月間成熟。在此次試驗中成功地促其產卵並發育達攝餌期仔魚 (眼睛已呈黑色的仔魚) 的最小型雌鰻之體重為623 g。催熟時程介於61-175天者，其仔魚之發育均曾達攝餌期的記錄。以魚塭培育之雌鰻作為催熟種鰻的來源之主要問題點為；卵細胞發育的不一致性及較無法精確地以體重指數 (BWI)，作為注射排卵素的依據。催熟的時間愈長，雌鰻在最後成熟階段的體重指數愈低。雄鰻則配合雌鰻成熟的進度，每1-2 週注射1-2 IU/g BW的HCG，可以有效地促進其精子的生成。

Pond-reared female Japanese eel Anguilla japonica, (n=210) with a mean total length of 83.2±6.3 cm (67.5-103.5 cm) and body weight of 1072±191 g (623-1700 g) were used for induction of maturation. The maturity of females was divided into 6 classes (classes 0-5) based on the black coloration of the pectoral fins. Females were injected with 0.5 or 1 IU/g BW of human chorionic gonadotropin (HCG) at 2 weeks interval in the first month in order to synchronize their maturity up to grades 3-4 one month after hormonal treatment. Subsequently, female with body weight over 800 g were injected with a dosage of 4 catfish pituitary homogenate, and 3 catfish pituitary homogenate for those with the body weight below 800 g. Accompanied with shortening of the injection interval, and reduction of injection dosage at the late stage of induction, final maturation can be attained in 2 months after hormonal treatment. Ovulation was induced by treatment of 17 , 20  - dihydroxy – 4 - pregnen-3-one (DHP, 2 g/g BW). Spawning was found occasionally in 100 L aquarium by mating with 3 - 5 males per fem ale. The goal of producing fertilized eggs all year around can be achieved by inducing the female broodstock to spawn in aquaria using DHP injection, with or without stripping 15-16 h after treatment. The onset of maturation in eel can be enhanced by treatment of HCG, and treatment of HCG together with catfish pituitary homogenate synergistically reduced the induction period. However, only 44.8 % of pond-reared female attained the final maturation. About 70% among matured female attained the final maturation stage within 2 - 4 months after hormonal treatment. The minimum size of female for successful spawning and producing the larvae until the feeding stage is 623 g. The induction period of females to produce viable feeding larvae ranged between 61 and 175 days. Asynchronization of oocyte development and difficulty in time decision for inducing ovulation based on body weight index (BWI) are the main problems of induction maturation in female eels, because the lower BWI was found in the female with long period treatment. For male, the spermatogenesis was induced by treatment of 1-2 IU/g BW HCG per 1 - 2 weeks interval in accordance with to the maturity status of female.
Key words: Anguilla japonica, Induced maturation, Human chorionic gonadotropin (HCG), 17, 20-dihydroxy-4-pregnen-3-one (DHP)