Abstract
The epidemic of ulcer disease of goldfish is in the spring. The condition is first observed in April and the diseased fish increase in number until June or July. Thereafter, the condition turns to cure till autumn. These facts suggests that the water temperature plays an important role in the etiology of this disease.
In the present study, two experiments were performed. In experiment 1, infection was artificially induced at different water temperatures from 2.5 to 30.0°C. The lesions could be induced within the range of temperature from 7.5 to 30.0°C. Incidence of the lesion exceeded more than 90% from 20.0 to 27.5°C. The terminal stage of the lesion was observed after 5 days at 25-27.5°C and 14 days at 12.5°C, respectively.
In experiment 2, diseased fish collected from culture ponds were kept in the tanks with water of different temperatures from 20.0 to 30.0°C and no antibacterial agents to observe the recovery pro-cess. The rapid recovery of the lesions was observed at the temperatures more than 27.5°C.
From these results, it is conceivable that the harmful temperature for the ulcer disease of goldfish is about 18 to 23°C, for within it the disease infection was easily and ulcer formation was much faster and not recovery.
