Populations of wild salmon from different rivers are genetically distinct due to their evolutionary adaptation to the specific characteristics of that river. As long ago as 1991, it was known that farmed salmon (critically lacking these specific genetic characteristics) were able to successfully breed with wild salmon, and more recent research has highlighted the reduction in genetic ‘fitness’ of subsequent generations in a process termed ‘out-breeding depression’. The extinction of specific wild populations of Atlantic salmon has been proposed as a possible consequence of repeated interactions of escaped farmed salmon with vulnerable wild populations.

The potential for escaped farmed fish to have a direct impact on wild populations of the same species is perhaps unique amongst modern farmed livestock animals, however with total farmed fish greatly outnumbering their wild counterparts, the potential for a significant impact must not be underestimated

Closed pens have been suggested as the only way to avoid escape related impacts on wild salmon, but organic principles would prohibit these relatively ‘unnatural’ systems from organic certification.

Over recent years, equipment failure has been the main cause of escapes in Scotland in recent years. Although only a small percentage were due to bad weather. While it may not ever be possible to avoid escapes due to extreme weather events, these figures show that a large reduction in escapes can be achieved simply by avoiding unnecessary equipment failure.

The banning of toxic nets means that nets on organic sites must be checked, cleaned and exchanged more frequently, providing increased opportunities to inspect equipment and prevent or reduce damage related escapes.

Improving pen designs, the use of modern materials and a better understanding of structural requirements in exposed sites should help to further minimise escapes in the salmon industry as a whole, however it is difficult for organic farmers to improve on these industry wide practices and initiatives.

Future developments in selective breeding may result in fish which are incapable of breeding with wild fish, but continued escapes during that domestication process have an increasing potential to damage the wild genetic structure until the end point of that process is successfully reached.

The potential for escaped-farmed salmon, including organic salmon, to have a negative impact on wild salmon and sea trout populations is a serious concern. The salmon farming industry as a whole has the ability to significantly improve its escape record, and is making considerable efforts to do so, however while open sea pens continue to be the industry’s typical holding unit, the risk of extreme storm related equipment failure remains.


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