Impacts of Open Pen Freshwater Aquaculture Production on Wild Fisheries

4 Conclusions

Several key points have emerged from this study:

• The theoretical potential for negative impacts on wild salmonids as a result of the presence of freshwater aquaculture is clear where they are physically coincident
• At a national level the large majority of the wild salmon and trout populations in Scotland are not physically coincident with freshwater pen sites
• The actual impacts on wild salmonid populations in Scotland from freshwater pen rearing of salmon and rainbow trout remain more or less unknown. Only a few studies, many quite old, have been carried out to date which address the question of actual interactions and impacts. These studies are restricted in the scope of their investigation on the question of impacts and are confined to investigations of single lochs
• There is no evidence of broad-scale impacts in terms of catch statistics and other obvious measures of wild salmonid stock/population health
• Freshwater pen aquaculture is only one of the several factors that might affect the health of wild salmonid stocks/populations
• Pen-farmed salmonids still escape, and therefore still offer a potential threat to wild salmonids - no matter how remote or how equivocal in terms of current scientific evidence
• There is evidence that some pen escapes have not been reported through the Marine Scotland mandatory self-declaration system
• The benefits of a change of policy now are by no means clear, taking into account current scientific knowledge
• The impact of financial costs on salmon production arising from restrictions in freshwater pen use to rear smolts range from minor to moderate in years of strong market prices and good profitability, to major or possibly prohibitive in years with poor prices and profitability. The impact on trout production is considered major or prohibitive throughout.

On the basis of the above key points and the other wide range of evidence gathered for this study, the authors conclude that:

• There does not appear to be a robust evidential case for suggesting radical and potentially expensive policy change regarding freshwater pen use.
• The least radical option in terms of costs would be mandatory improvement of containment. This would reduce but not eliminate most of the potential risks to wild stocks in those catchments in which pens are located. Tightening of the regulatory regime in this regard would not be unreasonable given the current state of knowledge regarding impacts. It would be logical for improvements in freshwater containment to go hand-in-hand with that for marine pens.
• Associated with improvements in containment, it is recommended that
  • A formalised regime of sampling for escaped fish in catchments containing pens should be established, independent of the industry self-reporting system that currently exists. Details of such a scheme require further consideration: scope of sampling, how much it would cost, and how it would be funded
  • Scientific Assessment of Impacts of Escapes . There should be a robust scientific assessment, probably on a specific catchment/project basis, of the actual impacts of farmed escapes, if and when they occur.