Aeromonus hydrophila, a Causative Agent of Mass Mortality in Cultured Japanese Catfish Larvae(Silurus asotus).

Abstract

The survival rate of larval Japanese catfish (Silurus asotus) during seedling production is usually very low due to cannibalism and mass mortality caused by unknown factors. Mass mortalities with the rate of 90-100\% occurred frequently among larvae reared at Gunma Prefectural Fisheries Experimental Station just before the advent of cannibalism. Aeromonas hydrophila and other species of bacteria were isolated from moribund 7-day-old catfish larvae, and examined for their bacteriological characteristics and sensitivity against 7 drugs. Experiments on intra-abdominal injections of the isolates into catfish and carp showed that the isolates of A. hydrophila killed 80-100\% of catfish and carp, and the bacterium was successfully re-isolated from the kidney of the experimental fish. A. hydrophila was. thus, suspected to be a causative agent of the mass mortality in catfish larvae.