الفهرس 
estimation of hearymetalsOnly 14 pages are availabe for public view
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Abstract
The freshwater crayfish Procambarus clarkii is an ecologically important species, which was introduced to Egyptian water during early 1980’s. It has been successfully established in various sites of The River Nile and its branches, particularly in the Delta region. The crayfishes have a considerable economic importance and play an important role in the ecosystem. As -it is a polytrophic crustacean animal that can serves as an effective organism in controlling species composition of freshwater ecosystem. They constitute a major food resource as well as a pest for men. The value of chemical composition of investigated samples was studied to determine the possibility of using the animals as an alternative •. source of food. The behaviour at the time of mating was observed because of its importance for the interpretation of field data obtained in population studies. Beside, study the effect of some heavy metals (eu & Zn) on the gametogenesis. The effect of the food items and photoperiods on growth rate was inve:stigatecl to determine the best methods for its culture.