This is a common disease often seen in intensive fish culture. It is caused by a bacterium whose exact identity is unknown. The bacterium first attacks the adipose fin, which will display a noticeable white line along the outer margin. As the disease progresses the adipose fin is destroyed and the bacteria will enter the caudal peduncle (tail) of the fish. Eventually the bacteria will cause the vertebral column to become exposed and become infected. When the disease is allowed to progress past the adipose fin it is always fatal.

Tail rot is associated with high rearing density and poor sanitary conditions in the rearing unit. The best treatment is prevention by keeping rearing units as clean as possible to prevent the growth of bacteria. A flow through treatment of Chloramine-T for 60 minutes at 8.0 mg/L is effective in eradicating the disease. Chloramine-T has not been approved for general use by the USFDA. Michigan hatcheries use this drug under a special permit (INAD) issued by the USFDA.