Studies on the Main Causes of Fish Moralities in Different Fish Farms and Aquaria

A total of 2693 of cultured fish from different farms (tilapiasp., mirror carp, mullet sp., sea bream and sea bass) were used forthis studies during the period from May, 1996 to June 1999, as wellas 20 water samples from the same fish farms during the previousperiod were obtained to study the occurrence or fish mortalitics indifferent fish holding facilities, its causes and their relation to thetype of fish, life stage, as well as water quantity, with recording ofclinical signs and pathological changes related to the fishmortalities. Also experimental studies on the acute and chronictoxicity of profenfose (Selecron) insecticide to the carp fingerlings, beside experiments to determine the pathogenicity of isolatedbacterial agents and trials for a treatment were carried out. Alsosome trials for treatment and control of fish mortal ities due to othercauses were carried out.The results showed that, the causes of fish mortalities couldbe categorized into: .I. Infectious causes:1- Bacterial infections:Duri ng the period from 1997 to 1998 , 3 occasions of fishmortalities due to bacterial infections were occurred in differentlocalities (Dakahila and Sharkia Gavernorates), involved bothtilapia sp. and mullet sp. resulting in death of 42,000 fingerlings oftilapia sp. and 450 fingerlings of mullet sp. from these occasionstwo bacterial agents were isolated, Aeromonas hyDROPhila and