Scientists have created a genetically modified 'monster' salmon which could soon be on dinner tables around the world.
A U.S. company claims it has been given initial approval by American safety authorities to produce the GM fish which grow two to three times faster than normal varieties.
The net result is that the fish convert their feed to muscle much more quickly and can be killed for the table at a younger age, assuring producers bigger profits.
British scientists have also been working on genetically modified versions of tilapia fish and edible carp.
However, critics of GM food fear the technology leads to the creation of mutant misshapen fish and could harm wild populations if they escape.
Research on GM trout in Canada found that while they grew faster and were many times larger than the wild species, they were likely to die before maturity and a number developed deformed heads and bloated bodies.
Genetic engineers at Aqua Bounty, a company based in Waltham, Massachusetts, have been manipulating fish growth hormone to make the GM salmon grow more quickly. This involves taking genes from the ocean pout and the chinook salmon, which trigger the release of growth hormone in the GM fish during their development.
One year after the salmon eggs hatch, those that have been genetically modified reach an average of 1,340g, compared to 663g for the ordinary Atlantic salmon. The AquaAdvantage salmon reach a marketable size within 18-24 months, as opposed to 30 months for the normal variety.
Supporters of GM foods have always argued that there are no significant differences compared with those grown or bred through conventional means.
Aqua Bounty takes the same view of its salmon, which has been nicknamed the 'Frankenfish' by critics.
Chief executive, Ron Stotish, said: 'In every measurement and every respect, these fish are identical to Atlantic salmon.'
The firm hopes U.S. veterinary authorities will approve its GM salmon eggs for this year's breeding season.
In theory, the fish would then go into stores and restaurants by 2012.
It seems likely that a pack of GM salmon would have to be identified on the label in a supermarket. However, there is no requirement to label GM fish on restaurant menus, which means diners may consume the salmon without realising it.
The campaigning consumer and green group GM Freeze is anxious about the arrival of GM fish. Its director, Pete Riley, said: 'We are extremely concerned about the potential for these fish to escape.'
Aqua Bounty said there is no danger of its fish cross-mating with wild fish because only female eggs that have been treated to ensure they are sterile will be created.