AquaGen, the Norwegian salmon breeding company, is this year delivering a million genetically engineered 'triploid' salmon to farms in Norway.
The salmon have three sets of chromosomes instead of two, making them sterile.
Ingeborg Myhr, the acting director of the GenØk Centre for Biosafety, warned that because of this, the new salmon might reach an unnatural size.
"Salmon stop growing when they reach sexual maturity. Would sterile salmon continue to grow so that we would get the media talking about 'monster salmon at large'?," she asked.
Triploid salmon have previously suffered serious skeletal weaknesses which have made them unviable for salmon farming.
But AquaGen has developed a special diet, which when fed to the parr (juvenile salmon) offsets the problem. The salmon will be harvested in 2015.
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Nina Santi, a spokesperson for AquaGen, said that using sterile fish was the best way to prevent GM salmon escaping and breeding in the wild.
"With farmed fish in the sea there remains the possibility that human error will result to an escape, so to avoid the industry needing to move on land, it is better to look for a solution with sterile farmed fish."