A jet ski equipped with an “acoustic startle device” is being used to scare seals out of the River Dee in order to protect spawning salmon.
For years, the Dee District Salmon Fishery Board has been working to reduce the number of seals which swim upriver from the sea and feast on fish in the Dee.
Although only a small number of the marine mammals make the journey up the river, the fishery board is concerned about the impact they are having on struggling salmon population numbers.
In order to help safeguard the fish from the predators, the board has for the past few weeks had its fisheries protection officers jump on a jet ski and ride around in an attempt to “displace seals downstream”.
Lorraine Hawkins, river director with the board, said the action is being taken now because spawning season is “a key moment to protect the salmon”.
How does the jet ski method work to rid the Dee of visiting seals?
Lorraine explained that in the past, the board has tried all sorts of methods to deter seals from coming up the River Dee.
From acoustic deterrent devices placed in the water that are “uncomfortable for a seal to hear”, to trying to shoo them back to the mouth of the Dee by standing at the riverside, no approach so far has yielded consistently good results.
But she hopes that the new trial technique of attaching one of the sound devices to a jet ski and getting it out into the river could prove to be a winner.
Lorraine said: “Seals usually live along the coast and don’t generally venture upriver, but we’ve just got a handful that seem to specialise in coming up the Dee, some as far as Banchory, 20 miles inland.
“Individually, they can have quite the impact on dwindling salmon numbers.
“They’ve been coming upriver for a few years now, but this year is by far the worst, which is why we’re trialling this new method.
“The jet ski is a way of getting the acoustic deterrent a bit closer to the seal, and shepherd it downstream, towards the coast.
“It’s not every single day we’re doing this by any means, but it’s enough to stop the seals from habituating to living in the river.
“We’ve only just started it, but the couple of times we’ve trialled it so far do suggest it resulted in the seal swimming downstream, so it’s a good starting point.”
Lorraine explained the acoustic devices being used utilise a “sound frequency specifically targeted at seals”, and said it shouldn’t harm any other river denizens.
Currently, the initiative is targeting the lower parts of the River Dee, particularly downstream of Drumoak.
Salmon numbers dropping in the River Dee
Lorraine said the move to use jet skis on the River Dee is in response to the “salmon crisis, and the fact that numbers of salmon are dwindling, not just on the Dee but throughout their range”.
She continued: “We are in the peak of salmon season right now, so it really is a key moment to protect the salmon.
“The way we most frequently measure salmon numbers and salmon populations is the rod catch in the year.
“Last year, 2021, Scotland had the lowest salmon catch on record — so it’s not just the River Dee, just about all the rivers in Scotland are really struggling.
“This year we have caught just over 3,000 salmon on the River Dee, and that is about 50% of what were seeing about 10 years ago, so that’s quite a drop in just 10 years, and part of a long-term decline of salmon numbers in the Dee.”
Conversation