The “From Headwater to Headland” conference, which took place in Berwick-upon-Tweed in March 2017, examined the critical issue of salmon and sea trout smolt survival in the early stages of their migration, from their headwaters of origin to the first stage of their life at sea. The presentations given at the conference are already available online here: AST YouTube Channel – From Headwater to Headland; and the Atlantic Salmon Trust and the Tweed Foundation have now published a report discussing the main issues it covered. This has been published as a new edition to the AST Blue Book series and can be download here: AST Blue Book – From Headwater to Headland
The report highlights the key points that emerged. For example, it is increasingly clear that the timing of smolt migration is influenced by the length of the journey to the sea and the likely temperature of the sea when they arrive; populations evolve to migrate at the optimum time for their native river. But climate change is disrupting the process, with smolts migrating earlier, when they are smaller and more vulnerable, and entering the sea when there is a mismatch between the river and colder sea temperatures. All this reduces their chances of survival.
Other important factors that influence smolt survival are pollution in freshwater, which reduces their general fitness and ability to adapt to life at sea, barriers to downstream migration and predation. Moreover, these all interact which each other: a smolt weakened by pollution and held up by a weir will be especially vulnerable to predation by other fish or by birds.
A final over-arching section of the report reviews the outcomes of the conference in relation to future research and management needs, with an emphasis on developing measures to improve smolt survival in the face of the many pressures identified during the conference.
The Atlantic Salmon Trust and Tweed Foundation thank the conference sponsors for their support: