author(s)
Pabitra Saharia, Hemanta Pokhrel, Binod Kalita, Inam Akhtar Hussain and Saidul Islam

abstract
High incidence of mortality in fish was recorded due to Aeromonas infection in carp culture system in the central valley of Brahmaputra region, Assam. Infected fish showed mostly gross ulcerative lesion on the skin with erosion of scales and fin and tail rot. Aeromonas hydrophila was dominant among the isolated bacteria from kidney, liver and skin of infected fish. Experimental infection in L. rohita with isolated A. hydrophila showed clinical signs with weakness, anorexia, swimming closer to surface, darkness in color with hyperemia and lysis of the fins. While, fluid accumulation in the abdomen, swollen liver, spleen and kidney with clear histopathological alterations were visible internally in moribund fishes. The study indicates that A. hydrophila is capable of causing pathological changes indifferent organs in L. rohita and cause mortality of affected fish in culture systems.