الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Tilapia is now one of the most common important groups of aquaculture species; the Nile tilapia, Oreochromis niloticus is a widely cultured species because it grows and reproduces in a wide range of environmental conditions and tolerates stress induced by handling.
In Egypt, tilapia is the most popular cultured fish, because of its tolerance of a wide range of environmental conditions, such as high and low water temperature, low oxygen content, high salinities, somewhat acidic or alkaline water as well as its utilization of food from the lowest trophic levels.
This work aimed to increase the growth rates and to improve the reproductive performance, fecundity and flesh quality of Nile tilapia Oreochromis niloticus using easy ways that can be achieved in hatcheries.
This study was done by formulating three diets with different protein ratios 25%, 30% and 35%, and these diets were allocated at a ratio of 2% of body weight daily to brooders of two different sizes of Nile tilapia (150±2 g and 251.5±3.5g), that were cultured in hapas installed in concrete ponds, at a rate of (4 fish/m3) during the spawning period which was about 120 days. Growth parameters, condition factor, maturity stages, fecundity, relative fecundity, hatching rates, gonadosomatic index and chemical composition of muscles were studied.
The physico-chemical characteristics of water were measured during the experiment, and all of its parameters were with the accepted range for tilapia spawning.
The best SGR value was found in the small group (for both males and females) fish that were fed on 35% protein diet.
The best FCR value was found in the small fish group (for both males and females) that was fed on 35% diet protein.
The condition factor values at the end of the experiment were comparable for both males and females, and were ranging between 1.46 ± 0.07 – 1.99 ± 0.05.
The account relative fertility, fecundity, hatching rate, total ovulation and the gonadosomatic index were studied and their results are shown in tables.
The biochemical analysis of muscles:
The moisture content, crude protein, total lipid and ash content of muscles were analyzed.
Microscopic examination of ovaries was carried out, it was found that oocyte of Oreochromis niloticus passes through five stages of development, which are:
Stage 1: The immaturation stage Stage 2: The maturation stage.
Stage 3: The vacuolization stage. Stage 4: The yolk deposition stage. Stage 5: Ripening stage.