الفهرس 
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Abstract
The present experimental work was carried out in the Department of Physiology, Biochemistry and Pharmacology, Faculty of Veterinary Medicine (Moshtohor) Zagazig Univer-sity (Benha), Egypt, during the period extended from March 1991 to April 1992.
The aim of the present work was; (1) study the normal physiological pattern of reproduction in female mature Clarias lazera fish including the cyclic variation of serum GTH (LH), estradiol, G.S.I and morphological changes of ovaries during all months of the year (2) The effect of injection of exogenous human chorionic gonodot-ropin and gonodotropin releasing hormone plus Dopamine antagonist (Domperidone) on GTH (LH), maturation and ovulation in fish with postvitellogenic stage in March, April, June July and August (3) The effect of these hormones on the level of estradiol, G.S.I and diameter of oocyte in non spawning season as atrial to get the postvi-tellogenic oocyte.
The results obtained revealed that :
1-Serum GTH (LH) level was moderately increased from March to April then attained Maximum from May to August with the peak at June.
2-Marked significant increase in estradiol level in April and remained high from May to August, then declined from August to February. 3-The G.S.I increased progressively from April to July attained its maximum in June then gradually decreased from August to reach its lowest level during December and January.
4-Ovarian structure differ according to the period of the reproductive cycle. During May to September, ovaries are in the postvitellogenic stage which consider as breeding or spawning season in Clarias lazera in Egypt. During October to February, ovaries are in atretic and previtellogenic stage, which can be considered as rest-ing period. The period of April to May, ovaries are in endogenous and exogenous vitellogenesis and can be considered as full gametogenic period.
5-Injection of HCG and sGnRHA plus Domperidone to the fish in postvitellogenic stage increase the level of serum GTH (LH) to the ovulatory surge Just prior to oocyte maturation and ovulation.
6-Injections of HCG to fish in postvitellogenic stage able to induce maturation and ovulation while sGnRH and domperidone failed to induce ovulation.
7-Injection of HCG and sGnRHa plus domperidone to female Clarias lazera fish in non spawning season (November) change the structure of its ovaries from previtello-genic stage to postvitellogenic stage with increase in estradiol level, G.S.I. and diameter of oocyte. It seems possible to concluded that :
a)The female Egyptian Clarias lazera fish have a long breeding season extending from May to August. The creteria used are, the presence of postvitellogenic oocytes, high levels of GTH (LH) and estradiol and high values of GSI. Unfortunately although it has long breeding season but it can not ovulate more than one time per season (Synchronous type), which mostly occurred during June.
b)Injection of exogenous HCG to female Clarias lazera fish having ovaries contain postvitellogenic stage of oocyte during the long breeding season which extending from May to August to induce maturation and ovulation could change the nature of ovaries of C. lazera fish from Synchronous type (which can spawn once per year) to A synchronous type which can spawn several time per breeding season. This will increase egg production by the fish during the breeding season and by artifical fertilization we can increase fish production to over come the shortage of animal protein for human consumption.