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Fisheries and Oceans Canada (DFO), under the Aquaculture Science Environmental Risk Assessment Initiative, is conducting a series of assessments to determine potential risks to Fraser River Sockeye Salmon (Oncorhynchus nerka) due to pathogens on marine Atlantic Salmon (Salmo salar) farms located in the Discovery Islands area in British Columbia (BC). This document is the assessment of the potential risk to Fraser River Sockeye Salmon due to viral haemorrhagic septicaemia virus IVa (VHSV-IVa) on Atlantic Salmon farms in the Discovery Islands area of BC under current farm practices. All the VHSV detected in BC belong to the genotype IVa, therefore, this risk assessment focuses only on the risk associated with genotype IVa. The assessment was conducted in three main steps: (1) likelihood assessment which includes four consecutive steps (farm infection, release, exposure, and infection assessments); (2) consequence assessment; and (3) risk estimation. Viral haemorrhagic septicaemia virus has occasionally been reported on Atlantic Salmon farms in BC between 2002 and 2019, it is therefore unlikely, with reasonable certainty, that Atlantic Salmon infected with VHSV would be present on one or more Atlantic Salmon farm(s) in the Discovery Islands area in any given year. Despite knowledge gaps around the infection dynamics and shedding rates of VHSV in Atlantic Salmon, it was concluded that the release of the virus from infected farms was extremely likely, with high certainty, given evidence of horizontal transmission of the virus in cohabitation trials. However, the release of the virus through vectors or fomites is unlikely, with reasonable certainty, under the current farm practices given that effective biocontainment measures are in place. It was concluded that the likelihood of juvenile Fraser River Sockeye Salmon to be exposed to VHSV through seawater during migration was unlikely, with a reasonable certainty, given the limited temporal overlap between Fraser River Sockeye Salmon and occurrence of VHSV on farms. Of the five years (out of 18; 2002-2019) in which VHSV was reported, only one year had evidence of VHSV during the time period that juveniles migrate through the Discovery Islands area. For adult Fraser River Sockeye Salmon, it was concluded that the likelihood of exposure to VHSV through seawater during migration was extremely unlikely, with a high certainty, given there was no temporal overlap between the migrating adults and the occurrence of VHSV on Atlantic Salmon farms in the Discovery Island area. It was concluded that the likelihood of juvenile and adult Fraser River Sockeye Salmon to become infected with VHSV is extremely unlikely with reasonable certainty given that Sockeye Salmon are not susceptible to VHSV infections. As the consequences are dependent on the susceptibility of Sockeye Salmon, the magnitude of consequences to the abundance and diversity of Fraser River Sockeye Salmon are both estimated as negligible. As Sockeye Salmon are not susceptible to VHSV infections, without infection, there will be no consequence (which is captured in the negligible consequence category) to the abundance and diversity of Fraser River Sockeye Salmon attributable to Atlantic Salmon farms in the Discovery Islands area. Overall, the assessment concluded that VHSV attributable to Atlantic Salmon farms in the Discovery Islands area poses minimal risk to Fraser River Sockeye Salmon abundance and diversity under the current farm practices. [ABSTRACT FROM AUTHOR]

Fisheries and Oceans Canada, under the Aquaculture Science Environmental Risk Assessment Initiative, is conducting a series of assessments to determine potential risks to Fraser River Sockeye Salmon (Oncorhynchus nerka) due to pathogens on marine Atlantic Salmon (Salmo salar) farms located in the Discovery Islands area in British Columbia (BC). This document is the assessment of the potential risk to Fraser River Sockeye Salmon due to Tenacibaculum maritimum on Atlantic Salmon farms in the Discovery Islands area of BC under current farm practices. The assessment was conducted in three main steps: first, a likelihood assessment which includes four consecutive assessment steps (farm infection, pathogen release, exposure of Fraser River Sockeye Salmon, and infection of Fraser River Sockeye Salmon); second, a consequence assessment; and third, a risk estimation. Mouthrot has commonly been reported on Atlantic Salmon farms in BC, it is therefore very likely, with reasonable certainty, that Atlantic Salmon infected with T. maritimum would be present on one or more Atlantic Salmon farm(s) in the Discovery Islands area in any given year. Despite knowledge gaps around the infection dynamics and shedding rates of T. maritimum in Atlantic Salmon in BC, the bacterium is extremely likely, with high certainty, to be released from infected farmed fish given the evidence of horizontal transmission of the bacterium in cohabitation trials. Given evidence of mouthrot on Atlantic Salmon farms while juvenile and adult Fraser River Sockeye Salmon are migrating through the Discovery Islands area, it is very likely, with reasonable certainty, that at least one juvenile or adult will be exposed to T. maritimum attributable to the farms in any given year. Taking a conservative approach in this risk assessment, Sockeye Salmon were assumed to be susceptible to infection with T. maritimum. Given the limited direct interaction of Fraser River Sockeye Salmon with farm sites, the lack of published reports of clinical signs associated to T. maritimum infection in Sockeye Salmon and the five positive detections of T. maritimum out of 2,006 juvenile Sockeye Salmon sampled around and north of the Discovery Islands area, it was concluded with high uncertainty that it is unlikely that juvenile Fraser River Sockeye Salmon will become infected with T. maritimum attributable to Atlantic Salmon farms in the Discovery Islands area under the current farm practices. Given that mouthrot is primarily a disease of concern for farmed Atlantic Salmon smolts, no report of mouthrot in the second year of production, very limited direct interactions of returning adults with the farms, quick migration of returning adults to freshwater, it was concluded with reasonable uncertainty that it is very unlikely that adult Fraser River Sockeye Salmon will become infected with T. maritimum attributable to Atlantic Salmon farms in the Discovery Islands area under the current farm practices. The potential magnitude of impacts on the abundance and diversity of Fraser River Sockeye Salmon was determined to be negligible given that mortality attributable to T. maritimum infection from Atlantic Salmon farms was estimated to be less than one percent. This conclusion was made with reasonable uncertainty. Overall, the assessment concluded that T. maritimum attributable to Atlantic Salmon farms in the Discovery Islands area poses minimal risk to Fraser River Sockeye Salmon abundance and diversity under the current farm practices. [ABSTRACT FROM AUTHOR]

Fisheries and Oceans Canada, under the Aquaculture Science Environmental Risk Assessment Initiative, is conducting a series of assessments to determine risks to Fraser River Sockeye Salmon (Oncorhynchus nerka) due to pathogens on marine Atlantic Salmon (Salmo salar) farms located in the Discovery Islands area in British Columbia. This document is the assessment of the risk to Fraser River Sockeye Salmon due to Moritella viscosa on Atlantic Salmon farms in the Discovery Islands area of BC under current farm practices which was conducted in three main steps: first, a likelihood assessment which is the outcome of four consecutive assessment steps (farm infection, pathogen release, exposure of Fraser River Sockeye Salmon, and infection of Fraser River Sockeye Salmon); second, a consequence assessment, and third a risk estimation. Moritella viscosa and winter ulcer have been reported on Atlantic Salmon farms in BC. Based on detections and/or winter ulcer diagnoses since 2012, it is very likely, with reasonable certainty, that farmed Atlantic Salmon infected with M. viscosa will be present on one or more Atlantic Salmon farm(s) in the Discovery Islands area in a given year. Shedding rates from Atlantic Salmon infected with M. viscosa have not yet been quantified; however, the bacterium has been isolated from skin lesions. It is therefore extremely likely, with reasonable certainty, that M. viscosa could be released from an infected Atlantic Salmon on a farm. M. viscosa detections and/or winter ulcer diagnoses have been reported on Atlantic Salmon farms during the months of December to February, while the migration timing of Fraser River Sockeye Salmon in the Discovery Islands area occurs from May to October. Given the lack of temporal overlap between M. viscosa occurrence and the Fraser River Sockeye Salmon migration, it is extremely unlikely, with reasonable certainty, that at least one juvenile or adult Fraser River Sockeye Salmon would be exposed to M. viscosa released from the Atlantic Salmon farms in the Discovery Islands area in any given year. The infection assessment was not performed given the outcome of the exposure assessment. The likelihood assessment concluded that it is extremely unlikely that an infection with M. viscosa attributable to Atlantic Salmon farms in the Discovery Islands area will occur in Fraser River Sockeye Salmon. Given the lack of temporal overlap resulting in the likelihood assessment concluding that it is extremely unlikely that Fraser River Sockeye Salmon would become infected with M. viscosa released from Atlantic Salmon farms in the Discovery Islands area, the consequence assessment was not performed. Overall, the assessment concluded that M. viscosa attributable to Atlantic Salmon farms in the Discovery Islands area poses minimal risk to Fraser River Sockeye Salmon abundance and diversity under the current farm practices. Conclusions of this risk assessment should be revised if winter ulcer on Atlantic Salmon farms in the Discovery Islands area were to occur between May and October. [ABSTRACT FROM AUTHOR]

Fisheries and Oceans Canada, under the Aquaculture Science Environmental Risk Assessment Initiative, is conducting a series of assessments to determine risks to Fraser River Sockeye Salmon due to pathogens on marine Atlantic Salmon farms located in the Discovery Islands area in British Columbia. This document is the assessment of the risk to Fraser River Sockeye Salmon due to piscine orthoreovirus (PRV) on Atlantic Salmon farms in the Discovery Islands area of British Columbia (BC) under current farm practices which was conducted in three main steps: first, a Likelihood Assessment which is the outcome of four consecutive steps (a farm infection assessment; a release assessment; an exposure assessment; and an overall infection assessment); second, a Consequence Assessment; and third, a Risk Estimation. PRV, of which only the PRV-1 genogroup is found in the Eastern Pacific, is endemic to BC where it has been detected both in wild and farmed salmon. PRV infections are ubiquitous, highly prevalent and persistent on Atlantic Salmon farms in BC; it is therefore extremely likely with high certainty, that farmed Atlantic Salmon infected with PRV would be present on one or more Atlantic Salmon farm(s) in the Discovery Islands area in given year. Shedding rates from PRV-infected Atlantic Salmon have not yet been quantified; however, laboratory studies provide evidence that infected Atlantic Salmon can shed the virus. It is therefore extremely likely, with high certainty, that PRV could be released from an Atlantic Salmon farm through infected fish. PRV stability in seawater has not been characterized; however, given evidence of temporal overlap between PRV on Atlantic Salmon farms and migration timing of Fraser River Sockeye Salmon in the Discovery Islands area, it is extremely likely, with reasonable certainty, that at least one juvenile and adult Fraser River Sockeye Salmon would be exposed to PRV released from Atlantic Salmon farms in any given year. Finally, under such exposure, given evidence of infection in cohabitation studies, it was concluded that it would be very likely, with high uncertainty, that at least one Fraser River Sockeye Salmon would become infected. Overall, it was concluded that it is very likely that at least one Fraser River Sockeye Salmon would become infected with PRV released from Atlantic Salmon farms in the Discovery Islands area under current farm practices. The potential magnitude of consequences to the abundance and diversity of Fraser River Sockeye Salmon was considered to be negligible given that current evidence cannot support the conclusion that PRV-1 causes disease or mortality in Sockeye Salmon. This conclusion was made with reasonable certainty and reasonable uncertainty for potential consequences resulting from juvenile and adult infection, respectively. Overall, the assessment concluded that PRV attributable to Atlantic Salmon farms in the Discovery Islands area poses minimal risk to Fraser River Sockeye Salmon abundance and diversity under the current farm practices. Conclusions have been reached based on a series of rankings estimated with a range of uncertainties. Conclusions should be reviewed as new research findings fill knowledge gaps. [ABSTRACT FROM AUTHOR]

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