Atlantic Salmon Arc Project

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.