Epidemiologic survey on incidence rate of fin rot in cultivated rainbow trout (Oncorhynchus mykiss) in Urmia, Iran

Objective: To determine incidence rate of fin rot in cultivated rainbow trout (Oncorhynchus mykiss) in Urmia, Iran and to identify environmental factors affecting the incidence rate of fin rot. Method & Materials: Questionnaire from 10 fish farms of rainbow trout in Urmia, Iran, was completed in summer 2008. Questionnaire was designed to gather epidemiologic data from cultivated rainbow trout. Then sampling was performed randomly. From each pond 100 fish were surveyed to determine fin rot incidence rate. Then, physico-chemical characteristics of water of each pond was measured, separately. The consuming feed of the fish was also undergone nutritional analysis using GC. Association between ration total fat and fin rot was studied using SPSS statistical software. Results & Conclusion: The surveys and statistical analyses showed that incidence rate of fin rot in cultivated rainbow trout farmed in rectangular and circle ponds were 70% and 57% respectively. Mean value of incidence rate in the rainbow trout farms of Urmia was 65.47% .Results of this study also showed that the highest incidence rate of fin rot related to dorsal fin and the highest rate of fin rot was seen in fingerling fish and the lowest rate in juvenile fish. Fin rot incidence rate in larvae, fingerling, juvenile and adult were 71.66%, 76%, 57% and 61%, respectively. Affecting environmental factors and their association with incidence rate of fin rot showed significant difference between fin rot rate and density of fish (p<0.01) and total fat of the ration (p<0.05). The results showed that there was a direct relationship between density of fish (19 number/m3 to 857 number/m3 ) and fin rot rate (30% to 85%). Based on results showed the increase in feeding (increase organic load of the fish ponds) the increase in incidence rate of fin rot.