الفهرس 
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Abstract
This work was conducted in the Central Laboratory for aquaculture Research at Abbassa, Sharkya Governorate to study the effect of some heavy metals (cadmium and copper) on growth performance, residues in different body parts and chromosomal behaviour in two species of Tilapia. Oreochromis aureus and Tilapia zillii with 15 and 13 g initial weight, respectively were used in this experiment. LC50 test, based on results previously obtained out of two sublethal levels from both cadmium and copper were selected for the present experiment. These selected levels were 2.2 and 1.1 p.p.m/l for cadmium and 2.0 and 1.0 p.p.m/l for copper. Fish from each species were divided into 10 groups with 15 fish each. Fish groups were randomly allocated to glass aquaria in doplicates (2 groups I treatment). Fish were fed on artificial diet containing about 28 % protein at 3 % live body weight daily for the duration of the experiment. The results of this work showed that: 1- Cadmium and copper caused a significant reduction in averages of survival weight gain, daily gain and specific growth rate of both Oreochromis aurous and Tilapia zillii as compared with the control fish group. 2- Feed conversion ratio (FCR) and protein efficiency ratio (PER) were depressed in fish groups grown in water polluted with cadmium and copper at the concentrations studied as compared with the untreated fish groups. The adverse effect was related to the level of these metals.