The publication of that assessment initiated the public comment period, now extended to April. After reviewing the comments — more than 30,000, so far — the F.D.A. will be free to issue its final ruling.

WE should all be rooting for the agency to do the right thing and approve the AquAdvantage salmon. It’s a healthy and relatively cheap food source that, as global demand for fish increases, can take some pressure off our wild fish stocks. But most important, a rejection will have a chilling effect on biotechnological innovation in this country.

Some scientists may move abroad, to China, Argentina, India or another nation where the political climate is more favorable. (Indeed, some have already done so — researchers at the University of California, Davis, who have developed goats whose modified milk could be used to treat and prevent childhood diarrhea, are moving much of their operation to Brazil.) Others may decide not to pursue such research at all. If a company that has done everything right can’t get its product approved, who else will be foolish enough to embark upon this kind of research? Who will finance it?

Of course, all this would be just fine with some anti-biotech groups, which traffic in scare tactics rather than science. But it shouldn’t be fine with the rest of us.

Genetically engineered animals could do real good for the world. Scientists at Cambridge University and Scotland’s Roslin Institute — the facility that created Dolly, the cloned sheep, in 1996 — have been working to genetically engineer chickens that are resistant to bird flu. They haven’t pulled that feat off yet, but they have managed to engineer birds that can’t spread the flu to others in their flock, which is a good start. Given how hard it is to develop vaccines to combat the rapidly evolving flu virus, this genetic modification could end up saving the lives of many birds, and perhaps humans.

Then there’s the Enviropig, a swine that has been genetically modified to excrete less phosphorus. Phosphorus in animal waste is a major cause of water pollution, and as the world’s appetite for meat increases, it’s becoming a more urgent problem. The first Enviropig, created by scientists at the University of Guelph, in Canada, was born in 1999, and researchers applied to both the F.D.A. and Health Canada for permission to sell the pigs as food.

But last spring, while the applications were still pending, the scientists lost their funding from Ontario Pork, an association of Canadian hog farmers, and couldn’t find another industry partner. (It’s hard to blame investors for their reluctance, given the public sentiment in Canada and the United States, as well as the uncertain regulatory landscape.) The pigs were euthanized in May.

The F.D.A. must make sure that other promising genetically modified animals don’t come to the same end. Of course every application needs to be painstakingly evaluated, and not every modified animal should be approved. But in cases like AquaBounty’s, where all the available evidence indicates that the animals are safe, we shouldn’t let political calculations or unfounded fears keep these products off the market. If we do that, we’ll be closing the door on innovations that could help us face the public health and environmental threats of the future, saving countless animals — and perhaps ourselves.