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 University (Benha), Egypt, during the period extended from February 1994 to February
1997. The aim of the present work was., (1) study the effect of some stress factors on reproduction of mature female C. lazera like overcrowding, temperature and handling, the parameters of reproduction are level of estradiol, gonadosomatic index (G. S. I) and vitellogenesis with ovary morphology (2) study the effect of presence of male, rising
water upto 25°C and controlling illumination 12h light &12 h darkness on the pattern of vitellogenesis of female C. lazera fish during prespawning period we hopped to activate reproduction and breeding during prespawning season to
increase the economic in put.
The results obtained revealed that
1- The obtained results revealed that the normal cortisol level ranged between (8.67 - 10.53 ng/ml) with means of (9.6 ng/ml) and exposure to stressful) factors like crowding, temperature and handling elevated the level significantly.
2-The normal estradiol level was (389.82 - 573.29 pg/ml) with means of (481.55 pg/m1) and significantly decrease was observed after exposure to stressfull.
3-The G.S.I. decreased progressively after exposure to stressful] factors.
4-Ovarian structure changed according to the type of stress; Atretic follicles increased significantly in overcrowding of 10 fish / 50 litre of water and temperature while 5,2
fish / 50 litre of water and handling did not cause significant changes.
5-Presence of males with females with increasing water
temperature and controlling illumenation 12h light & 12h
dark during prespawning season (March) improve ovarian
activity and G.S.I and resulted elevation of estradiol
levels but did not cause complete maturation and ovulation.
General conclusion and recomendation :
The economic production will be improved when we provide the optimal condition suitable for maximum production. from the obtained results of the present investigation we can concluded that, in order to optimize the factors influencing fish production we should avoid bad, rough handling and capture during transportation or management.
Moreover we should minimise overcrowding to avoid its adverse effect as it exhausts energy, which finally retard growth and increase mortality. Also ambient temperature should be taken in consideration as one of the most essential environmental factors and should be maintained with in the optimal comfort levels of 20 - 25°C.
However we recomend further investigations about the regimes used for artificially induction of spawning during off spawning seasons (to increase breeding times). This seems to be a chieved by different regimes, like using male itself or its pheromones or gonadotrophins or using different photoperiods or photothermal periods.