Aeromonas caviae during mortality on nile tilapia and supplementation with vitamin c in the diet

Abstract

High mortality in cage-cultured Nile tilapia at Três Irmãos Reservoir, State of São Paulo, was evaluated. In a 52 day period, 1,245 fish died, with higher mortality between 23 and 34 days after the first clinical signs. Fish appeared healthy, but died after fed. Water analysis showed normal values, and was not related to mortality. The liver was pale and parasitological exam showed low number of Protozoa and Monogenoidea on body surface and gills. The isolates from the liver and kidney revealed the presence of Aeromonas caviae. After 10 days of supplementation with 1,000 mg of vitamin C/kg dry ration, the mortality reduced 58%. The raising of fish in intensive system and the low level of vitamin C in which the fish had been fed probably increased the susceptibility to bacteria and mortality, allied to inadequate handling. It is suggested vitamin supplementation for tilapia reared in intensive systems.