Comparison between heavy metal residues and their effect on African Catfish (Clarias gariepinus) and Nile Tilapia (Oreochromis niloticus)

: F ish are an important source of proteins of a high value. Bioaccumulation of heavy metals in aquatic animals causes serious threat for fish as well as human via persistent consumption of fish. This study aims to estimate the concentrations of some heavy metals (lead (Pb), cadmium (Cd) and chromium (Cr)) in fish muscles and water. Samples of fish muscles ( Clariasgariepinus and Oreochromisniloticus ) and water were collected from different farms in Sharkia province in Egypt from April to September in 2022. The concentrations of heavy metals had the order Pb> Cr > Cd. The highest values of metals were recorded for Pb in the examined fish while the lowest values were recorded for Cd and Cr. There is a variation in the concentrations of heavy metals in water between investigated farms. The highest values of metals were recorded for Pb in the water. a significant decrease in RBCs count, Hb conc., PCV% and WBCs compared with control group with significant increase in MCV, MCH values in farm B, C and D compared to control and the most pronounced significant changes was correlated to farm C. A significant decrease in phagocytic index and percentage were the recorded effect of heavy metals. The impact of heavy metals on biochemical parameters showed significant increase of AST, ALT, urea, creatinine, glucose and total lipids in the blood of examined fish, but total protein and total globulin, beta and gamma globulin revealed a significant decrease. They