Aquaculture and wild salmon

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Ian Roberts, a salmon farmer in B.C., in his letter of June 4, correctly criticizes me for claiming sea lice have been blamed as a major reason for the collapse of sockeye runs in the Fraser River. It is difficult to define a precise cause for the declines of some runs.

However, a number of recent scientific articles have shown correlations of proximity of salmon farms with wild salmon declines (e.g Connors, B.M. et al. 2012, Migration links ocean-scale competition and local ocean conditions with exposure to farmed salmon to shape wild salmon dynamics, Conservation Letters), and in the Cohen report to Michael Kent (Technical Report 1) it is suggested that Caligus sea lice should be considered as a candidate for parasite-associated mortality of sockeye salmon smolts, the stage migrating to sea.

Roberts, therefore, throws doubts on my criticism of Trevor Taylor’s column in my letter of May 25. Trevor Taylor’s main points were: (1) salmon escaping from aquaculture sites were not a matter of concern; (2) sea lice occur naturally, so are not a problem in farmed salmon; (3) infectious salmon anemia is a naturally occurring disease, and may equally affect wild salmon, which have a natural mortality rate of around 20 per cent.

Taylor was incorrect on all these points, which anyone can read up on Google. Too bad natural marine mortality isn’t 20 per cent, although we’d probably be up to our necks in salmon if it were. However, a nasty fact remains, that wherever salmon farms are located in proximity to wild salmon rivers, the local wild stock declines.  

John Gibson

St. John’s

Organizations: Google

Geographic location: Fraser River

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Recent comments

  • Petertwo
    June 12, 2013 - 09:57

    There has been concern regarding the relationship of wild salmon smolts going out to sea and the lower than expected returns of wild spawning salmon to the rivers. The smolts may be being infected with ISA by the lice having to pass through the area where the salmon are being farmed and not able to cope being juvenile and vulnerable. While it is said that ISA originates with wild populations of trout and salmon there is very little written about it historically, it is only since salmon farming, 1984, that is has come to even being realised and be a serious concern. The other concern is ISA is also known as an Orthomyxovirus, of which there are two noted strains the European and North American. This virus is of the same family as the avian flu and swine flu virus and there is some concern that it could also affect humans given the right conditions. Science Daily, article "Salmon Virus With Potential For Change", quoting Norwegian Turhan Markussen and the Norwegian School of Veterinary Science.

  • PaulNorthRiver
    June 12, 2013 - 09:57

    When DFO decided to allow massive Atlantic salmon feedlots to be established in the midst of wild salmon habitat, they rolled the dice on those wild fish populations and put the entire coastal ecosystem at risk. When DFO allowed these same Atlantic salmon feedlots to be established on Canada's Pacific coast, it became clear to me that science and the precautionary principle were being ignored in the interests of short-term gain. The picture is clear...DFO has dropped out of the business of protecting wild fish and their habitat. The Fisheries Act has been gutted to remove almost all reference to fish habitat. The decline of wild fish populations and industrial encroachment into the marine coastal environment will continue until Canadians act to stop it.

  • owen myers
    June 11, 2013 - 14:04

    John Gibson's is correct in his recent assertion that "wherever salmon farms are located in proximity to wild salmon rivers, the local wild stock declines." A recent study in Scotland by the Atlantic Salmon Trust found that wild salmon stocks in Scotland's aquaculture areas experienced a marked decline compared to salmon in rivers in non-aquaculture areas. This pattern has been reproduced everywhere that salmon aquaculture has set up. In recent years Salmon Farming propagandists have coordinated their information campaigns to put salmon farms in a better light. Examples of this are pro industry sites such as and the anonymous The fact is that these salmon farms are incubators of salmon diseases and should never have been allowed to open in the beginning. DFO have once again failed to do their job but I suppose we should be used to that by now.