الفهرس 
Review of lterature
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Abstract
Lake Manzalah is economically the most important Delta lake in Egypt as it provides about 30% of the domestic fish supply. The River Nile is considered one of the most important fishery resources in Egypt. In the present study the effect of pollution on Oreochromis niloticus at Lake Manzalah and River Nile was studied. Cadmium and lead are the main common heavy metals that are very dangerous to the fish. This study includes 6 main points:
1 Determination the percentage of Cd and Pb in collected water samples from Lake Manzalah and River Nile.
2 Determination the percentage of Cd and Pb in muscles (edible part of the fish).
3 Studying gonadosomatic index= Gonad weight (gm)/total body weight (gm) x 100.
4 Studying hepatosomatic index= Liver weight (gm)/ total body weight (gm) x 100.
5 Histological studies of liver, gills and gonads.
6 Ultrastructural studies in the testes during the spawning month. The present results showed that the concentrations of lead