Anja Murray: Epic migration of Atlantic salmon in jeopardy

Wild salmon can leap as high as three metres. Perhaps our ancient forbears were aware of the benefits of the rich fatty acids found in salmon flesh that can help our brains to function well, which would explain the folklore association between salmon, stamina and knowledge

A salmon leaps up a weir. In recent years, conservation efforts have been impressive. Picture: Owen Humphreys/PA Wire

Right now, wild Atlantic Salmon are returning to their natal rivers to spawn. They have left behind the rich oceanic upwellings of the north Atlantic, having travelled as much as 3,000 km to return home. The details of how exactly they find their way over such vast expanses of open ocean are still somewhat of a mystery to us, finding their way to the specific estuary, and then river, tributary and stream where their ancestors have been spawning for more than 10,000 years. As a result, the salmon in any given river are those with distinct genetic lineage that is unique to that river.

Each part of the journey has its own challenges to be overcome. After traversing the ocean and arriving in estuarine waters, each returning migrant must spend some time acclimatising in brackish water, as the transition from salt water to sweet fresh water is uncomfortable. Their skin and scales change tone from pure silver to yellows and browns that blend in better with river water, enhancing the chances that they may escape the paws and talons of potential predators.