Abstract
Among a batch of small specimens of yellow tail transferred to a fish farm of Miyazaki Prefecture from Kochi Prefecture the majority were found suffering from the same disease which proved to be a bacterial one as given in the following lines:-
1. Diseased fish were mottled black on back from anterior border of first dorsal to post-erior border of second dorsal as well as on lateral side of trunk. Bad appetite and anemia were prevalent; sometimes ulcer was seen in alimentary canal and on epidermis.
2. Blood congestion and swelling were evident in liver and kidney. Softening and weak-ening of their tissues increased with advancement of the disease.
3, General dilatation of sinusoid occurred inliver accompanied by pycnosis of nucleus of liver cell, Necrobiosis of liver cells spread along blood cell wall.
4. Shrinkage of renal corpuscles and their disintegration of urinary tubules, coupled with their degenerative fat-infiltration were also in the picture.
5. Sporadically necrobiosis was found along blood vessels of spleen. Ellipsoid tissue was degenerated and vaguely defined from red marrow.
6. Very remarkable catarrhal inflammation in the alimentary canal was seen, its inten-sity being worthy of noticing.
7. A kind of pathogenic bacteria (gram.negative, short rod-like one) was isolated from spleen and muscle of diseased fish and successfully inoculated in intact specimens of the same species and allied forms to cause similar symptoms, but less, sometimes not at all, in other remotely related teleosts.
