Monitoring of seasonal parasitic and mycotic problems affecting cultured oreochomis niloticus under semi-intensive system

الملخص EN

The study was carried out on 1000 Tilapia (O.

niloticus) collected from private and governmental semi intensive earth pond (Central Laboratory for Aquatic Research laboratory (Abbassa) in Sharkia Province, through the seasons of the year 2008.

The clinical signs and post mortem lesions of diseased fish were recorded.

Results of the study revealed that (721) and (80) fish were found to be infected with different types of parasites and fungal infection respectively.

The isolation and identification of parasites in infected fish including the following, 1-Protozoa: (Trichodina sp.

in a percentage (42%), of total parasitic disease in fish examined.

The research showed that Trichodina sp.

represented the highest rate of infection was observed in summer season (64.8%).

2-Trematodes: a-Monogenia (Cichlidogyrus liberianus and Cichlidogyrus arthracanthus (28%), the highest rate of infection was observed in spring season (38%).

b-Digenean encysted metacercaria (Centrocestes (5.9%), Clinostomum (5.2%), Euclinostomum (4.9%)),and the highest rate of infection were observed in spring (6.4%), winter (7.2%) and spring (8.8%) respectively 3-Nematodes: a-Acanthocephala (7.5%) and the highest rate of infection was observed in autumn season (8.8%).

b- Contracaecum (3%) and the highest rate of infection was observed in autumn season (4.8%).

4-Crustacea (Ergasilus (4.9%) and the highest rate of infection was observed in spring season (8.8%).

The isolation and identification of mycotic diseases in infected fish revealed that the Seasonal prevalence of saprolegniosis showed that the highest rat L.:: ^ jjg concluded the wide spread of parasitic diseases and to lesser tj.e mycotic one in cultured O.

niloticus under semi intensive .I? f- m in Sharkia province which may be due to the improper 1 iiiii^' sement practice in such farms.

The results revealed that late spring ^ critical times for the occurrence of parasitic diseases, At •-^sattie time the rigorousness of saprolegnisis on O.

niloticus ^tcially in winter season which is associated with severe mortalities *high economic losses must be considered.

So the application of the jUl system of management including good quality water, proper fefftrition and using of immunstimulant will decrease the negative Ifpacts of such diseases in their critical times of occurrence