FARMED salmon should be sterilised to prevent them breeding with wild fish and introducing genetic weaknesses, experts have urged.

New research shows that while salmon bred in captivity for food consumption are genetically different from their wild relatives, they are just as fertile, potentially damaging wild populations if they escape and breed with them.

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.

Lead researcher Professor Matt Gage, from the University of East Anglia's school of biological sciences, said: "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.

"The problem is that farmed salmon can escape each year in their millions."

He said a solution was to induce a condition called "triploidy", by pressure-treating salmon eggs just after fertilisation, so the fish grows as normal but with both sex chromosomes, which makes most of them infertile.