The abstract is:
The salmon farming industry uses coastal, temperate marine waters to culture salmon in flow-through net pens. As marine currents pass through salmon farms, pathogens are carried in both directions between two highly contrasting environments. When wild fish are infected with pathogens spilling from the farm environment, the natural mechanisms that work to prevent epizootics become inoperative. The 18-year decline of Canada's largest salmon fishery, on Fraser River Sockeye Salmon, triggered a comprehensive federal commission to determine the cause. Two of the recommendations from this commission call for removal of the salmon farms from the Discovery Islands of British Columbia (BC), a bottleneck in the Sockeye Salmon migration route, if the evidence indicates that the industry generates greater than minimal risk of serious harm to the Fraser River Sockeye Salmon. Risk is interpreted as a probability and ‘minimal risk’, in the context of the Precautionary Principle, as a cut-off level on the strength of the scientific evidence needed to justify precautionary measures. Here the available evidence of the risk caused by sea lice and viruses from salmon farms on wild salmon is considered. From this perspective, the evidence is unambiguous. Salmon farms in the region of the Discovery Islands generate greater than minimal risk of serious harm to Fraser River Sockeye Salmon. Furthermore, there is no evidence that the risk factors identified are specific to Fraser River Sockeye Salmon, as many of them apply to other areas and salmon species in the north eastern Pacific and globally.
From the introduction:
The threat to ecological systems posed by agricultural activity is significant . The risk of pathogen transmission from farmed to wild salmon has been demonstrated  and , and open-net sea-pen salmon culture is recognized as a coastal ecosystem modifier across trophic levels , epidemiologically linking vastly separated wild salmonid populations . There is also a long history of large-scale, unforeseen, negative consequences due to accidental import of exotic pathogens . It is the primary cause for disease emergence in wild fish , with potentially irreversible effects .  reported reduced survival and abundance of wild salmonids for all populations exposed to salmon farms in North America and Europe as compared to both (i) unexposed populations in Alaska and the western Pacific and (ii) less-exposed regions within salmon farming countries.
This image shows the resultant populations of Harrison and other Fraser River sockeye that migrate either past fish farms, or not past fish farms. You will see that the Harrisons that don't migrate past fish farms are doing far better.
This is the migration routes of Fraser/Harrison sockeye fry out to the Pacific, You will note the high number of fish farms on the route used by most of the Fraser stocks and why getting fish farms out of the ocean is important. You will see from the image above that Harrisons are doing just fine, but not the rest of the Frasers. Wonder why? Hmm.