Survival of young salmon (smolts) as they migrate from river to sea was the subject of an international conference in Berwick last year.
A recently published River Tweed Commission report ‘From Headwater to Headland’ highlights the conference’s key points.
Climate change is a consistent factor impacting on the migration patterns of smolts as they make their way from river to sea. They will be younger, smaller and less fit, reaching the sea when conditions are less than optimal: colder sea temperatures and reduced feeding opportunities reducing their survival.
There is evidence that smaller smolts are less likely to survive and that the smolt age is dropping, with smaller, 1+ smolts running to sea.
Other factors include natural predators, chemical pollution and man-made barriers to migration.
“Addressing smolt decline is an international aim and one of the most important things going on that we can actually influence,” said Fay Hieatt of the River Tweed commission.
“While our surveys show that stocks are healthy, the next step is that as many smolts get to the sea unhindered. It’s important they get the best possible start.
“Over the past 25 years we have removed as many barriers as possible and the water quality is good. Our focus now is on smolt behaviour and predators.”
Anglers blame birds for reducing smolt numbers and the Tweed Foundation is about to undertake a tracking study, in conjunction with the Wildlife Conservation Trust, to look at the movement of birds up and down the river.
“The Tweed Foundation are also building a smolt trap on Gala Water to trap and tag downstream migrating smolts to see how they behave going down river and how they cope with different water heights etc,” added Fay. “It is hoped this will show how many one, two and three year old smolts survive and return to the river.
“Salt water is a challenge and how quickly they transfer from fresh water to sea water is important.
“Our river is in the best possible condition it can be for fish and continued monitoring ensures we are doing all we possibly can for our fish in their nursery stage.”