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Heavy metals are surrounded with great care and special importance due to their highly toxic effects on fish, which is a part of human diet; they affect survivability, growth and reproduction of fish. The present study has been conducted to determine heavy metals (chromium, cadmium, zinc, copper, lead and selenium) bioaccumulation in the muscles of three fish species, Common carp (Cyprinus Carpio), Nile tilapia (Oreochromis niloticus) and Mugil cephalus (striped mullet) that were collected from a different location (Damanhour, Kafr El Dawar and El Mahmoudia) along- Boheira governorate in Egypt. The results showed a statistically significant (p˂0.05) difference between fish species in the concentration of the accumulated heavy metals in muscle of examined species. It was observed that heavy metals bioaccumulation in fish were in the order of Mugil cephalus ˃ Nile Tilapia˃ Common carp, furthermore, the most of these levels within the global permissible limits for muscles samples. [ABSTRACT FROM AUTHOR]

In fresh fish, the balance between the prooxidative and antioxidative factors, which control oxidative reactions, is maintained by numerous systems with prolonged storage time the control of oxidation is lost and the onset of lipid oxidation can no longer be prevented. Therefore, the enzymatic antioxidant activities (superoxide dismutase, catalase, glutathione reductase, Nitric oxide) and lipid peroxidation were determined in muscle tissues of farmed fish including (Common Carp, Mugil Cephalus and Tilapia) during freezing storage for 48 hours. The obtained results revealed that the mean values of Superoxide dismutase, reduced glutathione, catalase and total antioxidant capacity were decrease during freezing storage for 48 hours while Malonaldehyde and Nitric oxide were significantly increased during freezing storage. The relative concentration of antioxidants varies with the fish species as well as the type of fish muscle tissue. (The present study concluded that freezing treatment had a great impact on antioxidant system regardless the duration of freezing storage. Therefore, control of lipid oxidation in fish involves utilizing processing and storage techniques that do not greatly decrease the activity of antioxidants enzymes). [ABSTRACT FROM AUTHOR]