الفهرس 
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Abstract
Lake Manzalah is economically the most important Delta lake in northern part Egypt as affected by drainage water. Lake Bardawil is the least polluted wetland in Egypt as it is a protected area (control lake in the study). Cd, Pb and Cr were studied on Liza ramada and Dicentrarchus labrax. The running water and fish samples were taken at the same time (summer and winter, 2010) from both lakes.
1. Fish biology study
”b” value and condition factor ”K” of Lake Bardawil fish was higher than those from Lake Manzalah.
Water physico-chemical characteristics
Physical parameters 1.Temperature:. The average of air temperature and water temperature of Lake Manzalah was increased.
Chemical parameters 1.pH-value: pH value in Lake Manzalah water samples; is a high significance difference.
2.Alkalinity (CO3- - and HCO3- ): The maximum value of the total alkalinity was in Lake Bardawil.
3.Salinity The maximum value of the total salinity was recorded in water of Lake Bardawil.
4.Dissolved oxygen There was a high significance difference between dissolved oxygen values in both studied lakes.
5.Hardness (Ca++ and Mg++) The maximum hardness was in lake Bardawil water.
3. Heavy Metals in Water Lake Manzalah water was found to have higher levels of Cd, Pb and Cr and exceeded recorded safety limits in two environmental laws; No. 48/1982 and No. 4/1994.
4. Heavy Metals in Gonads Lake Manzalah samples have high levels of Cd, Pb and Cr and exceeded recorded safety limits in Egyptian Organization for Standardization and Quality Control (law No. 1993).
5. Histological and histochemical alterations
I. Testes The histological study of fish testes (Lake Manzalah) has delaying in spermatogenesis. The histochemical studies showed decreasing in total muco-polysaccharide, total protein contents and light materials DNA in the nuclei and RNA in the cytoplasm.
II. ovaries The histological results of fish testes (Lake Manzalah) has atresia, deformed zona radiata, necrotic oocytes and broken tunica albuginea. Histochemical studies showed a decrease in the total muco-polysaccharide, total protein contents. There is light materials DNA in nuclei and RNA in the cytoplasm.
6. Skeletal system studies: Thickness of the vertebral column of fish from Lake Bardawil is more thickness than those from Lake Manzalah.
In conclusion, the results reveals that there were accumulated heavy metals in gonads of two studied fish and impair their reproduction process. These findings recommended that improved water quality control and periodically environmental monitoring are necessary in El-Manzalah lake.