الفهرس 
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Abstract
The present study was carried out at Central Laboratory for Aquaculture Research (CLAR), Abbassa, Abo-Hammad, Sharkia, Egypt. Fish were collected both males and females of Nile tilapia (Oreochromis niloticus), which were kept in tank supplied with aeration condition and suitable temperature for living.
The work was divided into three experiments within three seasons (spring, summer and autumn), 48 fish were used in each season and were divided to four groups as three salinity degree 3, 6, 9 ppt in addition to control group (salinity zero), where spring season represented by T1, T2, T3 and T4, summer season represented by T5, T6, T7 and T8 and autumn season represented by T9, T10, T11 and T12, in addition of rearing larvae during autumn season which represented by T13, T14, T15 and T16, each group divided to three repetition.
The present study designed to investigate the effect of acclimation (for three seasons spring, summer and autumn) under three salinity degree (3, 6, 9 ppt) in addition to control group (salinity zero) on the reproductive activity and growth of tilapia nilotica in a water temperature ranged from 24 OC up to 32 OC on the following:
1- Study the effect of seasonal changes on the reproductive activity and growth of tilapia nilotica (Oreochromis niloticus) fry.
2- Study the effect of different water salinities on reproductive hormones.
3- Study the effect of different water salinities on some biochemical parameters.
4- Study the effect of different water salinities on some hematological parameters.
5- Study the effect of different water salinities on some growth performance of fries Nile tilapia.
from the previous results, it could be concluded that after studying the effect of seasonal changes and water salinity on the reproductive activity and growth of fry of tilapia nilotica. Nile tilapia (Oreochromis niloticus) can spawn and grow in water salinity from zero up to 9 g/l and water temperature from 24 up to 32 OC. changes in fish environment has direct effect on the physiological state, reproductive hormone and rearing fries but has no effect on the chemical composition of fish muscles. Finally fish can spawn and grow with environmental changes but with less efficiently.