MORE:
As assessment of the impact of hatcheries on wild salmon in the US found that evidence for pathogen transmission between farmed and wild fish was equivocal (Naish et al. 2007). Although Kurath and Winton (2011) provide evidence for greater wild to farmed transmission of certain viruses, there is support for a directional transfer of parasites from farmed to wild fish (Taranger et al. 2015). Although disease monitoring among captive populations (e.g., hatcheries) is routine, surveillance for disease in free-ranging populations is usually synoptic, anecdotal, or not performed at all, and represents a major information gap in understanding the interaction of farmed fish with wild fish. Furthermore, reduced fitness for sick wild fish is expected to make them vulnerable to predation and other hazards that rapidly remove them from observation. Host tropism is an important consideration for horizontal transmission between farmed and wild fish of different species. Some species are more vulnerable to developing disease upon infection. For example, coho and Chinook salmon are more vulnerable to bacterial kidney disease (caused by Renibacterium salmoninarum than Atlantic salmon and rainbow trout (Starliper et al. 1997).
The risk of exotic or introduced pathogen exposure is substantially reduced by the use of native fish, initially cultured in a pathogen-free setting. However, if the farmed fish become infected by wild fish or pathogens present in the environment, the high density of farmed fish within net pens could amplify transmission within net pens, as well as to wild fish in proximity to the pens. Numerous risk reduction measures mentioned above have been implemented by Cooke Aquaculture to reduce pathogen exposure (e.g., vaccination, judicious use of multiple antibiotics, biosecurity measures to limit pathogen spread, fallow period, an all-in-all-out operation, etc.). Furthermore, the additional measures mandated by WDFW in association with their January 2020 Aquaculture Permit are likely to minimize the risks even further by ensuring timely reporting and increased accountability. Based on the disease history for the PS net pens and the information considered above, we believe the consequences of response of all listed species exposed to pathogens are likely to be low.
As assessment of the impact of hatcheries on wild salmon in the US found that evidence for pathogen transmission between farmed and wild fish was equivocal (Naish et al. 2007). Although Kurath and Winton (2011) provide evidence for greater wild to farmed transmission of certain viruses, there is support for a directional transfer of parasites from farmed to wild fish (Taranger et al. 2015). Although disease monitoring among captive populations (e.g., hatcheries) is routine, surveillance for disease in free-ranging populations is usually synoptic, anecdotal, or not performed at all, and represents a major information gap in understanding the interaction of farmed fish with wild fish. Furthermore, reduced fitness for sick wild fish is expected to make them vulnerable to predation and other hazards that rapidly remove them from observation. Host tropism is an important consideration for horizontal transmission between farmed and wild fish of different species. Some species are more vulnerable to developing disease upon infection. For example, coho and Chinook salmon are more vulnerable to bacterial kidney disease (caused by Renibacterium salmoninarum than Atlantic salmon and rainbow trout (Starliper et al. 1997).
The risk of exotic or introduced pathogen exposure is substantially reduced by the use of native fish, initially cultured in a pathogen-free setting. However, if the farmed fish become infected by wild fish or pathogens present in the environment, the high density of farmed fish within net pens could amplify transmission within net pens, as well as to wild fish in proximity to the pens. Numerous risk reduction measures mentioned above have been implemented by Cooke Aquaculture to reduce pathogen exposure (e.g., vaccination, judicious use of multiple antibiotics, biosecurity measures to limit pathogen spread, fallow period, an all-in-all-out operation, etc.). Furthermore, the additional measures mandated by WDFW in association with their January 2020 Aquaculture Permit are likely to minimize the risks even further by ensuring timely reporting and increased accountability. Based on the disease history for the PS net pens and the information considered above, we believe the consequences of response of all listed species exposed to pathogens are likely to be low.
