The Impact of Environmental and Parental Conditions on Mass Production and Rearing Process of Oreochromis Species and Their Hybrid

Abstract

The aquaculture industry in Egypt is growing in recent years due to the

low productivity and the diminishing distribution of Tilapia in the last two or three decades because of some environmental changes and pollution problems. Other species increased on the expense of the perfect species O. niloticus and O. aureus. Therefore the trend is diverted now towards man-made intensive or semi-intensive fish cultures.

The availability of fish fry for cages and fish cultures spreading in Egypt have to be

supplied from artificial sources and not on the expense of the natural water resources to

avoid those natural resources being exhausted or over-exploited. Therefore, the present / study is based on the following objectives.

1. The best parent strains of O. niloticus and O. aureus have to be selected for fish culture as pure brood stocks. We used the biochemical identification in addition to the morphological and meristic features. The confirmation and correct identification of the pure parental species and the hybridized broods will help avoiding over population and competition and allows managerial decisions to be taken according to heterosis between the hybrids and the pure parental species.

2. A comparative study for spawning conditions in different tanks was also applied using different stimulating factors; hormonal and environmental, to optimize the conditions of spawning for better fry production. The cage culture also was studied under experimental (net-enclosure) and commercial (large cages) conditions.

3. Since the hybridization of Tilapia (Oreochromis spp.) is relatively recent innovation in Egypt, our study aimed not onJy to produce all male hybrid, but also to