Flavobacteria Isolated from the Milt of Feral Chinook Salmon of the Great Lakes

Abstract

AbstractFish diseases caused by multiple genera within the family Flavobacteriaceae (Phylum Bacteroidetes) are a major impediment to farmed teleosts. At least one fish‐pathogenic flavobacterial species (e.g., Flavobacterium psychrophilum) is transmitted from parents to progeny via infected sexual products, but the majority of research has focused on the role that ovarian fluid and eggs play in bacterial transmission. However, a handful of studies have revealed that milt can also harbor F. psychrophilum. Herein, we report on the isolation and molecular identification of multiple Flavobacterium and Chryseobacterium spp. from the milt of feral Great Lakes Chinook Salmon Oncorhynchus tshawytscha. Some of the milt‐associated flavobacteria were identified as well‐known fish pathogens (e.g., F. columnare, etiological agent of columnaris disease), whereas others were most similar to emerging fish pathogens (e.g., C. piscium) or were distinct from all our described Flavobacterium and Chryseobacterium spp., according to partial 16S rRNA gene sequencing and phylogenetic analyses. Although systemic F. psychrophilum infections were detected in the kidneys of 35% of the 120 sampled male Chinook Salmon, the bacterium was never detected in the milt. The findings of this study highlight the role that milt can play in the transmission of a diversity of flavobacterial species.