Only the brave: Scientists to ask if some salmon are too timid to survive

Salmon born with an adventurous streak might be more likely to perish because they swim into harm’s way, scientists suspect.

Fish are known to have traits such as boldness or caution and their personalities could contribute to their chances of survival.

Now experts are to study the DNA of salmon smolts from the Moray Firth to see whether some have inherited a genetic advantage.

Factors being considered will include their temperaments, metabolism and resistance to parasites or disease.

Tissue samples were taken from the fins of smolts being tagged for a project examining the reasons behind the collapse in Scotland’s wild Atlantic salmon population.

Early findings from the Missing Salmon Project have shown that half of the 850 tagged smolts did not make it out of their home rivers after embarking on their migration.

Only around 35% got as far as the sea, as another 10 to 15% vanished in the estuary.

Experts at the University of Hull will now analyse some of the smolts’ DNA to look for clues, such as whether a tendency to gain weight quickly boosts their prospects.

Dr Domino Joyce, senior lecturer in evolutionary biology at Hull, said: “We’ll know which of the fish have made it to the end of the river, which ones made it all the way out to sea, and another group which haven’t made it anywhere.

“We’re going to see if we can find any genetic differences between the groups.

“It depends on the reason the fish are being lost. If it’s completely predation then it might be that there’s no genetic differences and it’s purely random.

“But there could be things like differences in when they move. So if some of them are much more cautious and only move at night then they might be less likely to be predated.

“In fish and lots of animals, you do often see personalities. Boldness is quite a common personality trait in animals where they’re more likely to explore or come out of hiding.

“The genetic basis for things like that are difficult to find and it might be that we don’t find it.

“But it might be that there’s something there.

“It might also be that there are fish with a more efficient metabolism and are better at putting on weight so they might be more likely to make it down the river.”

The research – scheduled to take place over the next year – is part of a wider Cluedo-style investigation being led by the Atlantic Salmon Trust (AST).

Young salmon – or smolts – migrate to sea from the river of their birth before eventually returning to spawn.

But in the past 25 years, the numbers coming back have dropped by 70%, and fewer than 5% make a successful return journey. Last year was the worst on record

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.

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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.