Usain Smolt may hold clue to mystery

Earlier this year smolts were caught and tagged in seven rivers in the Moray Firth – the route taken by 20% of salmon leaving the UK.

Each smolt was assigned a number and those that had been sponsored by wellwishers were also given names, including Usain Smolt, Smolt Whisky and Single Smolt.

The smolts were then followed on their journeys as the tags – which had a battery life of six weeks – emitted signals to the 358 receivers placed in the rivers and estuary. One smolt travelled an incredible 200km from the River Shin to Fraserburgh in 14 days. Another gave a significant clue to its cause of death as it did an about-turn and began swimming upstream – but its tag would have been sending out a signal from the belly of another fish. But experts at the Atlantic Salmon Trust had not expected such high numbers to die in the freshwater environment. Now they are studying the 15 million “pings” sent out by the smolts’ tags to find out what killed them.

Mark Bilsby, chief executive of the Atlantic Salmon Trust, said: “We have fish which are missing in action. “We’re moving next to try and find what the different suspects are in the loss of these fish. “You use the acoustic tags to find out where fish go missing then you use different techniques to have at a look at what the likely suspects are.

“It’s about working through a range of suspects right down to one. It’s like Cluedo.” Many salmon experts believe that global warming and changes in the oceans are to blame for the catastrophic decline in the species’ population.