Genotyping of Flavobacterium psychrophilum Isolated from Chum Salmon Oncorhynchus keta in Hokkaido, Japan

Abstract

We examined matured female chum salmon Oncorhynchus keta returning to a river, at a hatchery three times a year between 2006 and 2008, and chum salmon fry suffering from bacterial coldwater disease at the same hatchery in 2008 for Flavobacterium psychrophilum isolation. The isolates were genotyped by plasmid and RAPD analyses. In adults, the frequency distribution of genotypes varied among different years but was seemingly similar among different sampling opportunities within the same years. The RAPD genotype of the isolates from fry was one of major genotypes isolated from their parental group, which suggests vertical transmission of the bacterium.