THE Tweed Foundation has recently received reports concerning a number of dead and dying fish in the Tweed, but the foundation’s director Nick Yonge says that the deaths are perfectly normal.
Diseased and dead fish can look surprisingly gruesome to passersby, in this case prompting concerned members of the public to contact staff at the centre after viewing the distressing sights.
However, Mr Yonge said: “It looks alarming but, in fact, is just a normal event.”
The fish are most likely to be salmon or sea trout that have already spawned – commonly known as kelts.
Mr Yonge explained that most Atlantic salmon do actually die after they have spawned, either in the river or after they have returned to sea.
“Very few recover and return for a second time as multiple spawners, although some do,” he said.
According to The Atlantic Salmon Trust, an estimated 90-95 per cent of all Atlantic salmon will die after their first spawning, with studies showing that on very rare occasions a fish may return for as many as four spawnings.
For The Tweed Foundation, the process of ascertaining whether fish have returned multiple times is similar to finding the age of a tree by its rings. Scale samples are collected from returning fish, from which biologists can “read” the growth rings that are laid down in the scales. These ‘concentric’ rings show the life cycle of individual fish.
Live fish that are spotted at this time of year may be covered in a fungus called Saprolegnia which appears as white or grey patches. These fish are most likely to be male and the fungus infection is usually a result of the fish having sustained physical damage or skin breakdown.