Environmental DNA from multiple pathogens is elevated near active Atlantic salmon farms

The spread of infection from reservoir host populations is a key mechanism for disease emergence and extinction risk and is a management concern for salmon aquaculture and fisheries. Using a quantitative environmental DNA methodology, we assessed pathogen environmental DNA in relation to salmon farms in coastal British Columbia, Canada, by testing for 39 species of salmon pathogens (viral, bacterial, and eukaryotic) in 134 marine environmental samples at 58 salmon farm sites (both active and inactive) over 3 years. Environmental DNA from 22 pathogen species was detected 496 times and species varied in their occurrence among years and sites, likely reflecting variation in environmental factors, other native host species, and strength of association with domesticated Atlantic salmon. Overall, we found that the probability of detecting pathogen environmental DNA (eDNA) was 2.72 (95% CI: 1.48, 5.02) times higher at active versus inactive salmon farm sites and 1.76 (95% CI: 1.28, 2.42) times higher per standard deviation increase in domesticated Atlantic salmon eDNA concentration at a site. If the distribution of pathogen eDNA accurately reflects the distribution of viable pathogens, our findings suggest that salmon farms serve as a potential reservoir for a number of infectious agents; thereby elevating the risk of exposure for wild salmon and other fish species that share the marine environment.

Comparison of Taut and Catenary Mooring Systems for Finfish Aquaculture

Finfish aquaculture has been expanding in areas like Norway and Canada over the last 20 years, and is projected to expand further in the next decades as the planet’s population and demand for seafood increases. Finding appropriate salmon farm sites is becoming increasingly difficult, as there are fewer protected nearshore locations available for development. As a result, there is interest in increased utilization of existing leases (i.e. permitted sites). These leases have a boundary in which the anchors and mooring lines must be contained. Reducing the footprint of the mooring arrangement will allow for an increased utilization of existing leases. A possible method to reduce the footprint of a spread moored salmon farm is to use a taut mooring rather than a chain catenary mooring. This requires the use of mooring materials and components that allows for handling of tidal elevation changes and wave action. This paper investigates the performance of a taut moored configuration with integrated Seaflex elastomeric mooring components in comparison with a conventional chain catenary configuration using dynamic analysis. The results show that a reduced footprint taut mooring configuration with integrated elastomeric mooring components can be substituted for a typical chain catenary mooring with no significant increase in peak mooring line loads at extreme sea states and significant reduction in peak loading at moderate and calm seastates.

Draft Genome Sequence of a New Zealand Rickettsia-Like Organism Isolated from Farmed Chinook Salmon

We report here the draft genome sequence of a rickettsia-like organism, isolated from a New Zealand Chinook salmon farm experiencing high mortality. The genome is approximately 3 Mb in size, has a G+C content of approximately 39.2%, and is predicted to contain 2,870 coding sequences.