First report of tenacibaculosis in wild-caught Pacific salmon.

Understanding disease dynamics in wild fish populations is essential for effective conservation and fisheries management, yet diagnosing marine diseases in wild organisms is challenging. Tenacibaculosis, a bacterial disease caused by Tenacibaculum spp., is emblematic of this challenge, having been widely reported in farmed Atlantic (Salmo salar) and Chinook (Oncorhynchus tshawytscha) salmon, but never confirmed in any species of wild Pacific salmon (Oncorhynchus spp.). Here, we present the first report of tenacibaculosis in wild-caught Pacific salmon. During holding experiments conducted with Chinook salmon captured in Barkley Sound, Canada in 2022, we observed external lesions in 16 of 99 fish and associated high mortality. Through molecular screening, analysis of genetic sequences, and microscopic localisation of the infectious agents present, we identified Tenacibaculum dicentrarchi as the likely causative agent of tenacibaculosis in the fish with the most severe lesions.