Concurrent jellyfish blooms and tenacibaculosis outbreaks in Northern Norwegian Atlantic salmon (Salmo salar) farms

• Published in: PloS one Vol. 12; no. 11; p. e0187476
• Main Authors: Småge, Sverre Bang, Brevik, Øyvind Jakobsen, Frisch, Kathleen, Watanabe, Kuninori, Duesund, Henrik, Nylund, Are
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 02.11.2017; Public Library of Science (PLoS)
• Subjects: Animals; Aquaculture; Aquaculture industry; Aurelia aurita; Bacteria; Bacterial diseases; Bacterial infections; Bacteriology; Biology; Biology and Life Sciences; Chemical analysis; Dipleurosoma typicum; Disease Outbreaks - veterinary; Disease transmission; Earth Sciences; Economic impact; Electron microscopy; Farms; Fish; Fish Diseases - epidemiology; Fish Diseases - etiology; Fish Diseases - microbiology; Histology; Jellyfishes; Management; Medicine and Health Sciences; Mortality; Norway - epidemiology; Outbreaks; Pens; Plankton; Polymerase chain reaction; Research and Analysis Methods; Salmo salar; Salmon; Scyphozoa - growth & development; Seawater; Sediments; Skin; Tenacibaculum; Tenacibaculum finnmarkense; Transmission electron microscopy; Water analysis; Norway
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0187476

Tenacibaculosis is an increasing problem in the Norwegian Atlantic salmon aquaculture industry causing significant economic losses. In September 2015, two separate outbreaks of suspected tenacibaculosis occurred at two Atlantic salmon farms in Finnmark County in Northern Norway. The events resulted in major losses of smolts newly transferred into seawater. Prior to, and during the outbreaks, large numbers of small jellyfish, identified as Dipleurosoma typicum (Boeck) were observed in the vicinity of the farms and inside the net-pens. This study investigates the possible link between the jellyfish, Tenacibaculum spp. and the tenacibaculosis outbreaks. Bacteriology, histology, scanning and transmission electron microscopy, and real-time RT-PCR screening were performed on both fish and jellyfish samples. Based on the findings, Tenacibaculum finnmarkense was found to be the dominant bacteria associated with the tenacibaculosis outbreaks at both sites and that D. typicum is unlikely to be a vector for this fish pathogenic bacterium. However, results do show that the jellyfish caused direct damage to the fish's skin and may have exacerbated the bacterial infection by allowing an entry point for bacteria.