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Summaries of the risk assessments for the Discovery Islands area

Fisheries and Oceans Canada completed nine risk assessments on pathogens known to cause disease from aquaculture operations in the Discovery Islands area.

Risk assessments
Summary of risk assessment Science advice reports and supporting documents Risk estimation
Infectious Hematopoietic Necrosis Virus (IHNV) IHNV is a virus native to the Pacific Northwest. IHNV can cause a disease called infectious hematopoietic necrosis (IHN). The virus can infect several salmon species with varying susceptibility. The disease can cause death of infected fish.

The risk assessment concluded that the risk to Fraser River Sockeye salmon from IHNV is minimal.

There are two key reasons for this:
  • industry vaccinates against IHN; and
  • if infection occurs, industry removes infected fish from the net-pens.
The main uncertainty is that the impact to Sockeye salmon from IHNV exposure in the marine environment is unknown.
Science Advisory Report 2017/048

Research Document 2017/071 - Oceanographic and environmental conditions in the Discovery Islands, British Columbia

Research Document 2017/073 - Characterization of Infectious Hematopoietic Necrosis Virus (IHNV)

Research Document 2017/072 - British Columbia farmed Atlantic Salmon health management practices

Research Document 2017/074 - Ecology to inform pathogen transfer risk assessments in the Discovery Islands, BC

Research Document 2017/075 - Assessment of the risk to Fraser River Sockeye Salmon
Minimal
Aeromonas salmonicida and furunculosis

Aeromonas salmonicida is a bacteria that is native to the Pacific Northwest. It is the cause of furunculosis in salmon and trout species around the world. Salmon with furunculosis may die.

The risk assessment concluded that the risk to Fraser River Sockeye salmon from A. salmonicida is minimal.

The key reason for this conclusion is that the amount of A. salmonicida that is estimated from an infected farm is lower than what is required to cause infection or mortality in salmon. Therefore, A. salmonicida from farmed salmon is very unlikely to infect Fraser River Sockeye salmon.

The main uncertainties are:
  • the number of fish with A. salmonicida infection on farms is unknown; and
  • there is a lack of information on what the consequences to Sockeye salmon from an infection that does not cause mortality.
Science Advisory Report 2019/017

Research Document 2019/016 - Characterization of Aeromonas salmonicida and furunculosis
Minimal
Piscirickettsia salmonis and salmonid rickettsial septicaemia

Piscirickettsia salmonis is a bacteria that can cause a disease called salmonid rickettsial septicaemia (SRS) in marine fish species.

To date, there are no reports of this disease in Sockeye salmon.

The risk assessment concluded that the risk to Fraser River Sockeye salmon from P. salmonis is minimal.

The key reason is that P. salmonis on a farm is very unlikely to infect Fraser River Sockeye salmon.

There are several uncertainties in this risk assessment. These include:

  • a lack of data on how much bacteria is shed by fish infected with P. salmonis;
  • how long the bacteria can survive in the marine environment; and
  • what the minimum dose is required to cause infection and disease.
It is also uncertain what the consequences at the population level are from infections that do not cause death.
Science Advisory Report 2019/020

Research Document 2019/020 - Characterization of Piscirickettsia salmonis and salmonid rickettsial septicaemia
Minimal
Renibacterium salmoninarum and bacterial kidney disease

Renibacterium salmoninarum is a bacteria that can cause bacterial kidney disease (BKD) in salmon. BKD is a global disease and is found in both freshwater and marine environments.

The risk assessment concluded that the risk to Fraser River Sockeye salmon from R. salmoninarum is minimal.

The key reason is that the concentration estimated on a farm is much lower than the one required to cause infection or death in Chinook salmon, which are more vulnerable to R. salmoninarum infection than Sockeye salmon.

There key uncertainty is that the minimum dose of R. salmoninarum needed to infect and cause disease in Sockeye salmon in the marine environment is unknown.

As well, there is uncertainty about the consequences of R. salmoninarum infections in one generation of Sockeye salmon on the next generation.
Science Advisory Report 2019/019

Research Document 2019/018 - Characterization of Renibacterium salmoninarum and bacterial kidney disease
Minimal
Yersinia ruckeri and enteric redmouth disease

Yersinia ruckeri is a bacteria that causes enteric redmouth disease (ERM). It is primarily a freshwater pathogen and rarely causes disease in healthy and unstressed fish.

The risk assessment concluded that the risk to Fraser River Sockeye salmon from Y. ruckeri is minimal.

The key reason is that Y. ruckeri infection on farms in the Discovery Islands area is extremely rare, and there is no evidence of spread within farmed Atlantic salmon in the area.

The main uncertainty in this risk assessment is the susceptibility of Sockeye salmon. To date, there is no evidence of ERM in Sockeye salmon.
Science Advisory Report 2019/018

Research Document 2019/022 - Characterization of Yersinia ruckeri and enteric redmouth disease
Minimal
Piscine Orthoreovirus (PRV)

PRV is a virus found in several countries around the world. There are three distinct types: PRV-1; PRV-2; and, PRV-3. To date, PRV-1 is the only group detected in North America. The virus can infect several salmon species, but the capacity of PRV-1 to cause disease varies from region to region, and between salmon species.

The risk assessment concluded that the risk to Fraser River Sockeye salmon from PRV is minimal.

The key reason for this conclusion is that there is scientific evidence that PRV-1 infection does not cause disease, mortality or swimming impairment in Sockeye salmon.

The key uncertainties for this assessment relate to:
  • how likely it is that Fraser River Sockeye salmon will become infected with PRV-1 from infected Atlantic Salmon farms;
  • a lack of data to estimate the concentration of PRV-1 from infected Atlantic salmon farms; and
  • and the minimum PRV-1 infectious dose for Sockeye salmon is unknown.
Additionally, there is some uncertainty associated with how to apply laboratory study results to interactions that occur in the marine environment.
Science Advisory Report 2019/022

Research Document 2019/035 - Characterization

Research Document 2019/036 - Risk Assessment
Minimal
Moritella viscosa

Moritella viscosa is a bacteria that causes winter ulcer. The disease occurs in farmed Atlantic salmon in the northern Atlantic Ocean. To date, there is no evidence of winter ulcer in Pacific salmon species in British Columbia.

The assessment concluded that the risk to Fraser River Sockeye salmon from M. viscosa is minimal.

The key reason is that infections on farms do not occur when Fraser River Sockeye salmon are in the Discovery Islands area.
Science Advisory Report 2020/043 Minimal
Tenacibaculum maritimum

Tenacibaculum maritimum is a bacteria found worldwide in several species of marine fish. It is an opportunistic bacteria that can cause disease in fish that are stressed. In BC, the bacteria causes mouthrot disease (also called yellow mouth) in salmon. Mouthrot typically affects smolts in their first year at sea.

The risk assessment concluded that the risk to Fraser River Sockeye salmon from T. maritimum is minimal.

One of the key reasons for this conclusion is that mouthrot is a disease that mainly affects young Atlantic salmon shortly after they are transferred from freshwater to the marine environment. Pacific salmon appear to be less susceptible than Atlantic salmon. Fraser River Sockeye salmon have a short and limited interaction with the farms in the area.

The key uncertainty is whether or not Sockeye salmon can get infected with T. maritimum and develop mouthrot. Nevertheless, the risk assessment assumed that Sockeye salmon are susceptible.
Science Advisory Report 2020/044 Minimal
Viral hemorrhagic septicemia virus (VHSV)

VHSV is the causative agent of the disease VHS, which can occur in a wide range of cultured and wild fish species in both marine and freshwater environments. Genotype IVa is the only VHSV type found in BC and the surrounding northeastern Pacific Ocean where it causes noticeable, recurring mortality events in Pacific herring and Pacific sardine. Less commonly, the virus has been detected in farmed and wild salmon. There are no confirmed reports of VHSV in Sockeye salmon in fish health records, published studies and surveillance studies, and together with the results from controlled laboratory studies demonstrate that Sockeye salmon are not susceptible to VHSV-IVa.

The assessment concluded that the risk posed by VHSV-IVa is minimal.

The key reason for this conclusion is that Sockeye salmon are not susceptible to VHSV.

There are few uncertainties in this risk assessment.
Science Advisory Report 2020/049 Minimal
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