الفهرس 
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Abstract
Intensive fish farming seeks to production of maximum quantity of
fish in a minimum of water inthis method all feed is supplied artificially and the management of water quality is the predominant factor. In this investigation four different intensive fish farms, El Manzala (earthen ponds), Nawa fish farm (concrete pond with continuous water exchange), El-Tal El-Kebeer (recycling system) and Abbassa fish hatchery, were subjected to study water parameters, mortalities and infectious diseases (parasitic, mycotic and bacterial) to determine the most common problems facing intensive fish culture in Egypt. Four different experiments dealing with study the effect of stocking density, rate of water exchange and degree of temperature on the growth performance of Tilapia spp. which represent the most suitable fish for intensive fish farming in worm water in Egypt. Beside determination the
effect of stocking density on the parameters of water quality. Trials of treatment and control of the most common problems (infectious diseases) is another objective. The results of the~e investigation revealed that: - Fluctuation of water temperature in different seasons of the year is the first problem facing the investigated fish farms: Leading to high mortalities in Tilapia specially in Winter season. - Depletion of oxygen to 3.5 ppm is the second problem especially in El Manzala intensive fish farm. - Improper stocking density and rising the concentration of ammonia is the problem facing recycling ~‘stem in El-Tal El-Kebeer. - Adverse environmental condition leads to higher mortality and higher
prevalence of infectious diseases (parasitic, myccitic and bacterial)
especially in recycling system (El-Ta! El Kebeer). - The most common bacterial agents affecting the intensive fish farm are
Aeromonas hydrophila and Flexibacter colwnnaris which occurred in
high percentage in summer season, as well as Pseudomonas fluorescens which occurred in high percentage during winter season. - The three bacterial agents were sensitive to chloramphenicol in vitro. - Trichodinasis and monogenetic trematodes are the most numerous groups of parasites found in investigated farms, as well as saprolegniasis was the secondary invaders to the weakened fish under the investigated ecological condition. - The parasitic and mycotic agents could be controlled by spraying the infected ponds with 40 ppm formalin, 0.4 ppm Dipetrix, or 0.12 ppm Brornex, respectively. - Stocking density was not a factor affecting the survival of Tilapia. - 1-ugh stocking density 40 fish/60 L water, bring with it at the same time an increase in total productiqn and a reduction in the individual growth
of the fish. - High stocking density accelerate the environmental deterioration which is detrimental to the fish. - Exchange 25% of water volume 3 times weekly was necessary to obtain high growth performance of Tilapia.