Farmed salmon should be sterilised to prevent them breeding with wild fish and introducing genetic weaknesses, experts have urged.
Millions of salmon escape from fish farms each year, and can get into wild spawning populations where they can reproduce and introduce negative genetic traits.
"Farmed salmon grow very fast, are aggressive, and not as clever as wild salmon when it comes to dealing with predators.
"These domestic traits are good for producing fish for the table, but not for the stability of wild populations". Lead researcher Professor Matt Gage said.
A fisherman on the River Tweed has landed the biggest salmon to be caught on Scottish waters since 1928.
Shamus Jennings caught a fish weighing 50lb - roughly the same as a 7-year-old boy.
"I dreamed about it that night and I have thought about it since, and I think for the rest of my life I will always remember that fish," Mr Jennings said of the salmon that took around 45 minutes to land.
After posing for a photograph, the fish was returned to the water.