If all goes as expected, genetically modified salmon will soon arrive on our dinner plates.
Armed with a gene from the ocean pout -- another kind of fish -- the new salmon, which originally hails from the Atlantic, grows twice as fast as its less endowed peers out at sea.
The Food and Drug Administration has concluded that the new salmon is safe to eat and safe for the environment, suggesting that approval is likely at a hearing planned for later this month. The decision would make the fish the first genetically modified animal allowed for human consumption.
Called AquAdvantage, the fish has revived controversies that already surround genetically modified organisms. The development also raises questions about the future of the environment, the future of evolution and the future of food.
"I think this is a precedent-setter on many levels," said Brian Ellis, a plant biotechnologist at the University of British Columbia, Vancouver. "This is a self-replicating animal whose life cycle is still not very well understood, and most of it takes place far beyond human intervention out in the ocean."
"We're looking here at a scenario where the fish might wind up sooner or later in the ocean," he added. "I think if we go down this route, we have to be prepared to accept some potentially unknown consequences."
For thousands of years, people have been shaping the genes of their crops, pets and livestock by simply breeding individuals with the most desirable traits. Technology first infiltrated the process in the 1990s, when scientists began inserting new genes into plants, giving them resistance to herbicides, pesticides and diseases.
While their ethical and environmental impacts are still a matter of much debate, GM corn and soybeans are now staples of industrial agriculture. Those and other crops -- including cotton, canola, and potatoes -- withstand the spray of chemicals, even as the weeds and bugs around them wither.
GM animals have taken much longer to gain acceptance, even though scientists have been conducting genetic experiments on catfish, tilapia and other fish since at least the early 1990s, said Jeff Hutchings, a fish biologist at Dalhousie University in Halifax, Canada.
Some fish have been engineered to produce insulin for diabetics, he said. AquaBounty, the company that made the new salmon, first sought approval from the FDA in 1995.
One reason for the cautious approach is that scientists don't yet know what would happen if GM animals escaped into the wild. In his work over the last decade, Hutchings has found that mixing farmed Atlantic salmon with wild varieties affects both the growth and survival rates of the wild fish -- usually in negative ways.
All species of wild Atlantic salmon are listed as endangered. Adding any type of new threat could throw them over the edge. Often, Hutchings added, genes that are inserted for one purpose have other unintended and unpredictable effects.
"It's fairly difficult to make precise predictions about what would happen if interbreeding took place between GMO and wild salmon," Hutchings said. "But almost certainly the consequences would not be positive for the wild salmon, particularly given their poor conservation status."
As part of an expert panel in 2001, Hutchings and colleagues recommended that, if approved, GM fish should be raised only in land-based facilities, not in aquatic pens that are prone to frequent escapes. The scientists also suggested a procedure that sterilizes eggs, which would prevent fish from passing on their genes, even if they did get into the wild.
"The chances of some negative evolutionary consequence from the approval or use of GM salmon is pretty low, if not negligible," Hutchings said, at least in comparison to the effects of other human activities. Some studies, for example, suggest that fishing pressure has changed the size and age at which some fish first reproduce.
Several major scientific panels, Hutchings added, have found no sign that GM salmon would harm human health in any way. Tissue for tissue, he said, GM salmon and wild salmon are indistinguishable.
Still, the public remains cautious. With so many unknowns, Ellis said, that may be for the best. Based on ongoing experiments with livestock, he imagines that fish are just the first step toward a future full of genetically modified meat, including beef and pork that are engineered to have ideal profiles of fat and protein.
"The science is amazing," Ellis said. "It's a reflection of how much we've learned about biological systems. The questions we have are a reflection of how little we know about biological systems. There is a lot of uncertainty out there, and there will be for a long time."