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Abstract
Diseases of freshwater fish increased in its importance in both wild and cultured systems. It lead to great economic losses in body gain, feed intake with increasing mortality level and decrease the productive efficiency of fish production farms as well as public health significance in certain circumstances. This study was carried-out for:
1. Exam the degree of fluctuation of bacterial infection in intensive and semi-intensive system in cultured O. niloticus.
2. Determination of the most important factors affecting incidence of fish diseases under Egyptian conditions.
3. Identification and characterization of the types of bacterial diseases that spread under Egyptian conditions.
4. Differentiation between the seasonal prevalence of bacterial infection in intensive and semi-intensive system in relation to water quality.
5. Advisement about measurements of prevention.
This study concluded that:
1-In general the maximum number of A.hyDROPhila isolates in semi-intensive system observed in summer and winter seasons, while in intensive system the maximum number of A.hyDROPhila isolates observed in autumn and spring seasons
2-High number of P.fluorescens isolates in both semi-intensive and intensive system observed in autumn, winter and spring seasons, while in intensive system the number of P.fluorescens isolates observed in summer season was higher than that of semi-intensive system.
3-Higher number of P.aerogenosa isolates in semi-intensive system observed in winter and spring seasons than that of intensive system, while in intensive system higher number of P.aerogenosa isolates observed in summer and autumn seasons than that of semi-intensive system .
4-The higher number of V.anguillarum isolates in semi-intensive system observed during spring season than that of intensive system, while in intensive system the higher number of V.anguillarum isolates observed during summer, autumn and winter seasons.