Wild Atlantic salmon start their lives in streams and rivers, migrate to the high seas to grow and then return home to spawn.
However, little is known about their migration routes as they leave Scottish rivers. An initiative using transmitters to keep track of the fish is now set to enter its second year, backed by £400,000 from the Scottish Government.
Atlantic salmon travel large distances to feeding grounds and can be found in far-flung places including the seas off Greenland.
But the species is now in serious decline and the West Coast Tracking Project is part of a broad range of measures seeking to help.
It involves tagging young salmon with miniature acoustic transmitters, each with its own unique signature, as their migration begins.
Strategically placed receivers record the signal from each tag, allowing the progress of individual fish to be tracked as they pass multiple listening sites.