INVESTIGATION ON MASS MORTALITY AND BIOACCUMULATION OF HEAVY METALS AND FISH PATHOGEN IN NILE TILAPIA (OREOCHROMIS NILOTICUS) IN FAYOUM GOVERNORATE

INVESTIGATION ON MASS MORTALITY AND BIOACCUMULATION OF HEAVY METALS AND FISH PATHOGEN IN NILE TILAPIA (OREOCHROMIS NILOTICUS) IN FAYOUM GOVERNORATE

Nashwa Abd El-Razek; Gehan I. Abd El-Bar Shagar

and Hala Fouad Ayoub

Fish Health and Diseases Depat., Central Laboratory for Aquaculture Research, Agriculture Research Center, Ministry of Agriculture, Egypt.

Abstract

The present study was carried out to determine the possible causes of an emergent event of mass mortalities among Oreochromis niloticus (O. niloticus) farms in Fayoum Governorate. Field visits had recorded thousands of dead large sized cultured monosex Oreochromis niloticus daily in many farms while huge numbers of fish of different size accumulated on the water surface showing typical signs of asphyxia manifested by gasping and rapid opercular movement. It was also noted that Fayoum water body is being subjected to agriculture drainage where accumulation of heavy metals. Results of bacteriological examination revealed that, all the examined 200 fish samples were infected with different types of bacterial isolates including Aermones sp (A. hydrophila, A. sobria and A. jandaei); Pseudomonas sp. (Ps. aeruginosa, Ps. Putida and Ps. fluresence) and Vibrio sp. (V. parahaemolyticus and V. alginolyticus). The physicochemical examinations of water samples and the analysis of heavy metals concentration in water and organs indicated marked abnormal water quality parameters and environmental pollution which might be incriminated as a primary stress factor that promoted the invasion of bacteria. The mean values of total ammonia were exceeded while the values of DO. and SD showed depletion than the permissible limit in farms 4, 2, 3, and 1 with the exception of temperature and PH. Iron was the most abundant element followed by zinc and cadmium, which higher than permissible limit in farm4. The conduction of sensitivity test on most prevalent isolated species A. hydrophila showed that it was susceptible to ciprofloxacin while A. hydrophila showed resistance to Oxytetracycline and Amoxicillin. The study concluded that both factors would have interacted to produce this catastrophic intense case of respiratory distress and mass mortalities. The impact of the recorded bacterial infection; environmental pollution and biochemical parameters were briefly discussed.

Keywords: Mass mortalities, Oreochromis niloticus , heavy metal pollution. bacterial isolates and Wadi El-rayan.