الفهرس 
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Abstract
A total number of 720 apparently healthy fishes of both Nile tilapia Oreochromis niloticus and African catfish Clarias gariepinus (360 for each) with average body weight 50±5 g for O. niloticus and 150 ±12 g for C. gariepinus were used to study the effect of water temperature and water total ammonia on growth performance and immunity.
This study was done in the World Fish Center, Abou Hammad, Sharkia province. Fish were kept at dissolved oxygen (6 ± 0.5 mg/L), water temperature (24 ± 2 °C), total ammonia (less than 0.02 mg/L along the course of the study, and the fish were fed by 3 % of the total biomass of fish twice daily.
A total number of 360 Fish (180 O. niloticus and 180 C. gareipinus) were equally divided into three groups with three replicates for each fish species (20 fish /replicate). In 1st group with 2.5mg/L total ammonia, the 2nd group with 5mg/L total ammonia and the 3rd group as a control where the total ammonia was zero mg/L.
Another total number of 360 Fish (180 O. niloticus and 180 C. gareipinus) were equally divided into three triplicate groups for each fish species (20 fish/ replicate). In 1st group water temperature of 28ºC, the 2nd group the water temperature was 32ºC and 3rd group as a control where the temperature was 24-25ºC.Mortality rate, weight and histopathological changes were recorded and blood samples were collected to determine some biochemical and immunological parameters.
The results revealed that water total ammonia (2.5mg/l and 5mg/l) affected growth, health, survival and resulted in increasing the susceptibility of fish to infection.