Occurrence of Flavobacterium psychrophilum at four rainbow trout hatcheries was investigated to proved more knowledge about the reservoirs and transmission of this bacterium. Incubating water, ovarian fluid, milt, unfertilized eggs, fertilized eggs, eyed eggs and fry stages were sampled. Flavobacterium psychrophilum was not found in milt while the pathogen was found ovarian fluid. Indicating that broodstock may serve as a reservoir and are latent carriers of the pathogen. F. psychrophilum was determined on eggs and from water samples. F. psychrophilum 44 isolates was isolated from four rainbow trout hatcheries in Fethiye region during January and February 2007. The F. psychrophilum isolates obtained from different farms proved to be homogeneously phenotipic characteristics. The F. psychrophilum isolates represented a biochemical and physiological characteristics were observed. Enzym production was tested using API ZYM strips. In the result of API ZYM test, the F. psychrophilum isolates produced lipolytic and proteolytic enzymes but not utilise simple or complex carbohydrates. Isolates from all of the four hatcheries studied showed differences in estrase and cyctin arylamidase production within a group.