A “secret slaughter” of seals is being carried out by fish farmers around the coastline of Scotland, campaigners have claimed.
The Seal Protection Action Group told the BBC’s Countryfile programme that as many as 5,000 of the mammals are shot in Scotland every year.
The salmon farming industry disputed the figure, and said shooting seals was necessary to protect stocks.
It is currently legal to shoot seals outside their breeding season.
Although seals have become one of Britain’s most iconic and best-loved wild animals, their love of fresh salmon has brought them into increasing conflict with a fish farming industry looking to cash in on the growing human appetite for cheap salmon.
More than one million salmon meals eaten in the UK every day, and the industry is one of the biggest employers in the Scottish Highlands.
Common seal numbers have plummeted by a third in Britain over the past seven years, with ecological changes and a shortage of wild fish generally thought to be behind the drop.
But Andy Ottaway, of the Seal Protection Action Group, said he believed the shooting of seals was another major factor behind the animal’s decline.
The group was established 30 years ago oppose the mass culling of seals on Orkney.
Mr Ottoway said: “Little did we realise then that the cull would simply be driven underground and continue in secret to this day.
“The seal shooting takes place in very remote locations in sea lochs around Scotland and there are no witnesses, and under the law the industry doesn’t even need to release the figures of the numbers they have killed.
“We believe there is a mass slaughter of seals in Scotland – up to 5,000 each year.”
Mark Carter, of the Hebridean Trust, said he believed the general decline in seal numbers was particularly noticeable in the areas surrounding fish farms.
“Scientifically we don’t know the real reason behind the total decline, but what we do know is that when they are situated near a fish farm then there is a decline and shooting is probably one of the main reasons,” he told Countryfile.
“We have got people who have actually witnessed the shooting on fish farms, and we have had several seals washed up with bullet holes in their heads.
“The problem is it is not just adults that find them – my children found one washed up on the beach in front of the house. We did an autopsy and the skull was completely shattered.”
It is not just conservationists who are worried. Donald McLean has been taking tourists seal watching in the Sound of Kerrera, off the west coast of Scotland, for 30 years.
The area is traditionally one of the best places in the world to see common seals in their natural habitat.
But Mr McLean said a big increase in the number of local salmon farms – there are currently some 300 in the area – had coincided with a sharp drop in seal sightings.
“When I first started you would come out and see between 60 and 80 seals on average, but now you are down to 10 or 20,” he explained.
Mr McLean claimed a large colony of seals which would regularly bask on a rocky outcrop in the Sound disappeared completely when a salmon farm opened up nearby and started shooting them.
But Scott Landsburgh of the Scottish Salmon Producers’ Organisation, said a single seal attack could kill several thousand farmed salmon.
He said: “The seals are very aggressive – they attack the nets and can bite through them, and they can also actually use their flippers to steal salmon out of the cages.
“It’s not just a few – it is thousands of salmon.
Indiscriminate attacks by seals can cause trauma throughout the cages and we can lose 2,000 or 3,000 salmon at a time, not only by attacking them but also just be being in the vicinity.”