A number of US supermarket chains pledged on [March 20] not to sell genetically modified salmon, in a sign of growing public concern about engineered foods on the dinner table. The US Food and Drug Administration (FDA) is in the final stages of deciding whether to allow GM salmon on to the market. If approved, AquaBounty Technology's salmon would be the first genetically engineered animal to enter the food supply. The GM salmon is the first [of some 30 species] of genetically engineered fish under development, including tilapia. Researchers are also working to bring GM cows, chickens and pigs to market. However, those plans could be blocked by Wednesday's commitment not to sell genetically engineered seafood from national grocery chains including Trader Joe's, Aldi and Whole Foods, as well as regional retailers. Between them, the chains control about 2,000 outlets. Campaigners said they represent a growing segment of the population that is concerned about GM food, and willing to pay higher prices for healthier foods. Critics of GM salmon say the FDA has not conducted proper oversight of the fish, which are raised from eggs hatched in a facility in Prince Edward Island, Canada, and grown to maturity in tanks in a remote area of Panama. They say there is insufficient data to back up AquaBounty's claims its salmon can grow to maturity twice as fast as wild salmon. They also dispute the company's claims that there is no increased risk to people with allergies.