Trawlers responsible for salmon decline?

The AST and its colleagues have been worried for some time that there may be accidental killing of salmon by pelagic trawlers at sea during migrations from and to their rivers of origin. The Atlantic Ocean SALSEA project confirmed the presence of salmon among catches of other pelagic species, such as mackerel and herring. 

The extent of such catches is not known, but it is certain that accidental by-catch does take place, probably in many parts of the Atlantic Ocean, including the Barents, Norwegian and North seas, as well as in the European western approaches and seas surrounding Iceland and Greenland. 

The risk of substantial loss of post-smolts and larger salmon later in their life cycle as accidental by-catch, gives urgency to finding ways of analysing the seriousness of that risk and, if it is found that it impacts on stocks, to find ways of remedying the problem. 

The AST estimates that for every 1,000 smolts that leave their rivers of origin an average of about 80 adult salmon return. If it were found that 2% of post-smolts are being killed accidentally by pelagic trawlers, there could potentially be 20% more adult fish returning. While there are many variables that could render such a claim unrealistic, it is clear that the potential increase is worth serious investment. It should also be noted that this model concentrates on post-smolts outward migration, and does not consider salmon killed at other stages in their lives.

The AST is therefore seeking partnership funding of £180,000 over three years to coordinate a project to:

•Assess and quantify the risk of accidental ‘by-catch’ to Atlantic salmon migrations.

•Define the areas and times of year when interception of salmon migrations is most likely.

•Discuss options for research and remedies with the Pelagic Regional Advisory Committee.

•With Pelagic Regional Advisory Committee (PRAC) partners devise methods of avoiding accidental damage to salmon migrations.

•Implement remedial measures then monitor, evaluate and report back to PRAC.

•Provide information for stakeholders and fishery managers of project efficacy.

The Trust has already invested over £50,000 in the development of the project, and will continue to invest its own resources.

Tony Andrews, Director of the AST, explains: “Wild Atlantic salmon are without doubt intercepted as a by-catch of commercial fisheries. Interceptions often occur at predictable times and in certain locations, probably to a greater extent than earlier anticipated. There is no doubt that the pelagic fleets will continue to seek out new grounds and that the efficiency of fishing vessels will increase. As they do so, further determined efforts will be required by the international community to quantify the extent of by-catch of salmon in these fisheries, and the opportunities for timely mitigation measures to be introduced.”