河鳗人工繁殖的初步研究

本文报道了自1973年以来河鳗人工繁殖研究的基本情况，包括亲鳗催熟、催产以及胚胎发育和培育等试验内容。试验结果表明，在人工催熟和水温逐渐升高的条件下，大部分亲鳗在4月上旬至5月中旬性腺成熟。从1974年至1978年总的产卵受精率为8．4％(其中流卵和产死卵者不计在内)。亲鳗自然产卵的时间一般在凌晨4时至6时20分之间，水温在18．5—24．5℃范围。产卵行为较特殊，产卵前发情时，雄鳗和雌鳗先后由池底阴暗处游至水表，沿池边环游追逐，最后在较小范围内急游产卵授精，产毕又回至池底。海水盐度在23—29．8‰范围，均能产卵受精，并孵出鳗苗。孵出后头两天的仔鳗悬于水表；第3天的仔鳗，卵黄囊大部分吸收，消化道全通，在肠内开始发现食物团，肠道内有强烈的纤毛运动，鱼体开始悬于水中，有极缓慢的下沉和上升；第4天眼球出现黑色素，晶体透明，上、下颌能启闭，有四对牙齿；第5天，肠道有蠕动波，出现肝脏原基，静止时侧卧水底；第14天，仔鳗在微流水中能不断游动，在静水中常处于水底。仔鳗养至第19天，存活434小时。

STUDIES ON THE ARITIFICIAL INDUCEMENT OF REPRODUCTION IN COMMON EEL

Studies on the artificial inducement of reproduction in common eel (Anguilla japon-ica) have been carried out since 1973. The parents were collected from Tai Hu. They were induced by injection with pituitary gland of carp and HCG. The results of induce-ment show that the females can be induced to mature by means of injecting with smalldosage of the gonadotrophie hormones at an interval between 15--20 days each time and5--6 times in total. All the females were matured in 7--8 times, and the method seemsto be of good effect. The spawning of common eel usually takes place in the early morning between 4:00and 6:20 A. M. at water temperature between 18.5--24.5C. The spawning place isjust under the surface of the sea water. Soon after spawning the females begin to takefood and gradualty restore to health. The remnant of ovary absorbs rapidly. Thesephenomena lead us to consider whether the gonad can redevelop and mature again. The 3--days old larvae demonstrated that the digestive organs are incompletelydeveloped, and the yolk sac is nearly absorbed. The intestine is filled with foods andwithin it there is a violent ciliary movement. This may be a kind of special method ofnutrition in transition. The larvae lived 19 days (434 hours).