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

PLoS One. 2017 Nov 2;12(11):e0187476. doi: 10.1371/journal.pone.0187476. eCollection 2017.

Abstract

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.

MeSH terms

  • Animals
  • Aquaculture*
  • Disease Outbreaks / veterinary
  • Fish Diseases / epidemiology*
  • Fish Diseases / etiology
  • Fish Diseases / microbiology*
  • Norway / epidemiology
  • Salmo salar
  • Scyphozoa / growth & development*

Grants and funding

The study was partially funded by the Research Council of Norway (Norges Forskningsråd) (Project number 241364, https://www.forskningsradet.no/prosjektbanken/#!/project/241364/no). This study was also partially funded by Cermaq Norway (www.Cermaq.no). Neither of these funders had a role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Cermaq Group AS received this funding. Cermaq Group AS provided support in the form of salaries for authors [SS, KF, ØB, HD], and also played a role in the study design, data collection and analysis, decision to publish, and preparation of the manuscript. Two of the authors [KW, AN] are employed by the University of Bergen (UiB); however UiB had no role in study design, data collection or decision to publish. The specific roles of these authors are articulated in the ‘author contributions’ section.