Abstract
A new bacterial disease, causing mass mortalities among pond-cultured ayu (Plecoglossus altivelis) in Shiga and Tokushima prefectures, was studied. Bloody ascites appeared to be the most characteristic sign of the disease. The causative organism was similar to Pseudomonas putida, but it did not produce fluorescent pigment and reduced nitrate to nitrite. Most of the isolates showed the API 20NE profile number of 1-140-457. An antiserum against the causative organism did not react with Ps. putida ATCC12633T.
