الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Aquaculture remains one of the fastest-growing food-producing sectors and is set to play a key role in meeting the rising demand for fishery products that consider one of the cheapest sources of protein, Nile tilapia is the most economically important Freshwater Fish in Abbassa Farms and the most popular in Egypt.
Water samples were taken from the two different farms Abbassa fish farms that located in Abbassa District, Abou Hammad, Sharkiya. The presence of Abbassa pool that was the base of Abbassa fish farms and the other is private fish farm in the way of Ismailia canal, Sharkiya Governorate.
One liter of water samples from taken from each of the two different farms irrigated with Agricultural drainage water samples by a PVC tube column sampler at depth of half meter from the water surface. Temperature and Dissolved oxygen was measured by using a digital oxygen meter. Hydrogen ion concentration (pH) was measured with pH meter, salinity, total ammonia and Heavy metals concentrations in water (mg/l) were measured after digestion with HNO3 and HCl.
In the 1st fish farm the mean metals concentration in the water of 1st fish farm decreased in the order: Fe > Mn > Zn >Cu >
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Cd > Pb, while in the 2ndfish farm was Fe > Mn > Zn > Cd > Cu> Pb.
All mean metals (Zn, Mn, Cu and Pb) concentrations in water were under the guiding lines set by (ECS, 1994). While Fe and Cd concentration their ratio exceeded the guiding lines. Fe concentration was 2.13 mg/L and 5.93 mg/L in both 1st and 2nd fish farm respectively and Cd concentration was 0.02 mg/L and 0.05 mg/L in both 1st and 2nd fish farm respectively. While Fe exceeded the guiding line value by 1.13 mg/L and 4.93 mg/L in both 1st and 2nd fish farm respectively, Cd also exceeded the guiding line value by 0.01 mg/L and 0.04 mg/L in both 1st and 2nd fish farm respectively.
The mean metals concentrations in the fish muscle tissues exceed permissible limits in the 1st fish farm was (Cu) exceeded by 0.9 mg/g dry weight and exceeded by1.69 mg/g dry weight in 2nd fish farm and (Fe) exceeded only by11.96 mg/g dry weight in the 2nd fish farm.
Fish samples were collected from the same two studied areas during the same period of water sampling. A number of 9 naturally diseased O. niloticus fish from each fish farm, with a total numbers of 18 fish. Fish were dissected to obtain samples from muscles, gills, and livers. They were dried in oven at 105 ºC over night then ignited in order to be converted into ash as a preliminary preparation for metals analysis. Many steps were
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carried out till analysis for Fe, Zn, Cu, Cd and Pb then measured using Atomic Absorption Spectrophotometer.
In both gills and liver of fish both studied area 1st and 2nd fish farm all mean metals concentrations exceeded permissible limits set by FAO/WHO, (1999). Except (pb) which was not detected in gills, liver or muscle tissues. The accumulation of metals was in liver with high values than gills and muscle tissues.
A total number of 100 naturally diseased O. niloticus fish randomly of different stages and different weights from two different fish farms were obtained alive and transported to lab. of fish health and management department in central lab for Aquaculture Research (El-Abbasssa), Sharkia during the period from December 2018 to May 2019. The fish were immediately subjected to clinical, post-mortem examination, Fungal and bacterial isolation and identification and histopathological abnormalities.
Naturally infected tilapia were characterized by some clinical signs