"We don't have any monster pigs in Europe, or monster cows, and there's no need for such a salmon," said Geir Isaksen, the chief executive at big Norwegian fish farmer Cermaq.

Genetically modified (GM) Atlantic salmon patented by U.S. biotech firm AquaBounty are widely billed as growing at double speed and could be approved by U.S. regulators as early as this summer, taking the global GM food fight to the fish counter.

"This is a safe and stable construct," AquaBounty CEO Ronald Stotish told Reuters, explaining how technicians inject Atlantic salmon eggs with genes from Pacific Chinook and bottom-dwelling ocean pout.

The result -- three species in one, thus transgenic -- would be the first GM animal approved for human consumption, joining GM plants like soy and corn that have been altered to tolerate harsh herbicides.

"If it (GM salmon) becomes a big thing, it's clearly negative for the existing salmon farmers," said Dag Sletmo, an analyst at Oslo investment bank ABG Sundal Collier.