الفهرس يوجد فقط 14 صفحة متاحة للعرض العام
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المستخلص
Grass carp is not a native breed in Egypt and can not be reproduced naturally under common Egyptian climatological circumstances, so, grass carp fingerlings were annually distributed in tributaries of River Nile. Unfortunately, uptill now, no study was carried out for evaluation of this policy through following up the health of the introduced fish. The aquatic environment with its water quality is considered the main factor affecting the fish health. Also, a wide variety of pathogens affecting fish are maintained under unfavorable environmental conditions. Consequently, fish can be used as biomarkers for environmental pollution. through analysis of the biochemical and histological changes as well as population dynamics.
In the present work, results of measurements of of physio-chemical parameters of water samples were detected. And the levels of heavy metals (Zn, Pb, Cu, Cr, Cd, Mn, Ni, Fe and Co) were also detected.
Bacterial analysis of water samples revealed the presence of microbial contamination, with total coliform, Fecal coliform and Fecal streptococci.
Great variation in weights and lengths and K-factor values were detected between sampled fish. In general, all examined grass carp fish were apparently healthy. However, gills of some fish showed slimness, erosion and marbling appearance. At the end of the observation period, fin congestion, skin haemorrhages and reddened vent were detected in some collected fish. The internal organs appeared pale in color, enlarged in size and friable in texture. The intestine appeared normally at all experimental period except in one parasitized fish.
The parasitological examination revealed the presence of Dactylogyrus sp., Trichodina sp. and Ergasilus sp. in gills of examined reared grass carp.
All samples taken from the liver and kidney were found to harbour various kinds of microorganisms. Vibrio sp., Salmonella sp., Streptococcus sp., Aeromonas sp., Coryneibacterium sp., Staphylococcus sp. and E. coli. The histopathological examination of the skin revealed exfoliation of a part of the epidermis associated with necrotic epidermal cells and accumulation of lymphocytes and leucocytes with activation of the goblet (mucus) cells. Muscle oedema ,coagulative necrosis and Encysted metacercaria occurred in some cases.
Gills showed damages and distorsion of the secondary lamellae. Also, there was oedema and swelling of secondary lamellae with narrowing of interlamellar space and degenerative changes, with necrosis and desquamation could be observed in some cases. More advanced changes, manifested by hyperplasia and lamellar fusion of secondary lamellae. These changes were associated with the presence of Monogenean sp., Trichodina sp. And Crustacean sp. lodged or floating singly in between the secondary lamellae.