Many organisations work hard to address bottlenecks in the lifecycle of the Atlantic salmon within river systems. Approaches can be at a catchment scale targeting diffuse impacts and habitat degradation or they can be at local scale addressing specific point issues. The impacts of these actions are positive and well documented. The proportion of salmon successfully returning from the sea to their natal river to spawn is, however, known to vary greatly between rivers and between years and the causes of the variation remain poorly understood.

There are many potential candidate factors: commercial exploitation, by-catch, predation, climate change and the variability in the quality and location of feeding grounds at sea. Some of these factors are natural and some are unnatural (caused by human action). The problem is that we don’t know which, if any, of these factors has a pervading influence. Some of these factors can be directly controlled, others cannot be controlled at all and others require political negotiation and even global political change. Understanding the causes of mortality at sea is however crucial for the sustainable management of Atlantic salmon.

So far information on natural and unnatural mortality at sea has been derived from tagging experiments. Salmon from a river are tagged and tags found in fish caught at sea are collected. The tagging of Atlantic salmon has thus far yielded vital but limited results. Too few fish are tagged and too few return to identify with any certainty a levels of natural and unnatural mortality.

The Westcountry Rivers Trust won ERDF funds to use genetic markers to identify the profiles of Atlantic salmon populations in river systems on the Western coast of Europe. Once a population is profiled, any fish from that population can be identified from a simple scale sample. It is anticipated that the method will provide a system whereby fish caught at sea can be assigned to their natal river or region. This will provide an invaluable shared resource for all involved, and once set up, data can continually be added and further conclusions drawn about the movements and mortality at sea of specific Atlantic salmon populations.

 The project was called the Atlantic Salmon Arc Project (ASAP) and was worth 1.5 million euros. ASAP was led by the Westcountry Rivers Trust and had an auspicious set of partners including World Wildlife Fund, Environment Agency, Atlantic Salmon Trust, Exeter University, University of Wales Bangor, Central Fisheries Board of Ireland, Association of West Coast Fisheries Trusts in Scotland, and all their equivalent organisations in Spain and France.