One day in 1992, a technology entrepreneur sat down for a meeting with a pair of biologists who were studying the genes of fish. The scientists, Choy Hew and Garth Fletcher, were working on a method of purifying “antifreeze proteins” that would help Atlantic salmon (Salmo salar) survive so-called superchill events in the North Atlantic. Normally these salmon migrate out of the subzero ice-laden seawater of the far North Atlantic to overwinter in less frigid waters. Increasingly, though, such fish were being farmed, penned year-round in offshore cages, in near-Arctic waters to which they were not adapted. Fish farmers were looking for a way to keep the fish alive through the winter, and the antifreeze protein seemed like a possible solution.

As the meeting drew to a close, Fletcher and Hew showed Elliot Entis, the entrepreneur, a photo of two fish of equal age. One dwarfed the other. “I sat back down,” Entis recalled recently.

But there is something about genetically engineered fish that many find uniquely disturbing. In a 2013 poll by The New York Times, 75 percent of respondents said they wouldn’t eat genetically modified fish. (That number dropped to two-thirds for other forms of GE meat.) The nation’s largest grocery chains, including Safeway and Kroger as well as Whole Foods and Trader Joes, have signed a statement saying they will not sell genetically modified fish.

There’s also a tangle of bureaucratic red tape to get through before GE fish finds its way into U.S. grocery stores. The U.S. Food & Drug Administration approved AquaBounty salmon for sale in this country more than two years ago, in November 2015. But an obscure rider attached to a budget bill by Alaska Senator Lisa Murkowski in December of that same year effectively blocked the FDA from allowing GE salmon into the U.S. That import ban still stands.

It’s a strange paradox: If you could get the fish here, you could sell them; but you can’t legally bring GE salmon into the country.

Opposition, naturally, is fierce. But to AquaBounty CEO Ron Stotish, bringing superfish to global markets is not just a promising business opportunity; it also has the potential to change an industry.

“We are providing technology to improve food production and make it sustainable,” Stotish says. This, he says, will put society in a better position “to address the global food security issues we’ll face as the world’s population approaches 10 billion.”

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Eager to see how AquaBounty got to this point and what the future of fish farming might look like, I travel to the company’s hatchery at Bay Fortune, on Prince Edward Island. The island—known as PEI—forms an arc in the southern Gulf of St. Lawrence, just off the coasts of New Brunswick and Nova Scotia. Driving out from Charlottetown to the far eastern peninsula, we pass small, picturesque fishing villages and tidy farms flying Canadian flags. AquaBounty’s lab and hatchery is a metal-sided, two-story building, painted the cheery shade of ocean blue that has become the company’s trademark color. Belying the research and engineering underway inside, the exterior looks more like a roadside warehouse than a lab for mad fish science.

Inside, in big green fiberglass tanks, swim the salmon: conventional and transgenic in separate tanks, each fish individually microchipped. Called “AquAdvantage Salmon” in the company’s marketing materials, the genetically engineered fish are more than twice the size of conventional fish at 12 months of age—around 1 kilogram (2.2 pounds) compared to 300 to 400 grams (0.7 to 0.9 pounds) for the regular salmon.

This is Fletcher and Hew’s innovation, pictured in the photo they showed to Entis 25 years earlier. Entis, whose father ran one of the first companies to import farm-raised salmon from Norway, had seen a revolution in the making. “The first thing I thought was, ‘My God, these guys don’t know what they’re sitting on.’ To raise fish in half the time, that has enormous implications. I pretty quickly realized that this is the kind of massive breakthrough that could be critically important to an entire industry.”

What Entis didn’t realize at the time was just how long it would take to bring that breakthrough to market—nor that he would no longer be there to see it through. Along the way, both Entis and Fletcher—who joined the company in 1994—were ousted.

In 2012, the company’s primary investor, Kakha Bendukidze, a biologist and entrepreneur who’d served as Minister of Economy in the former Soviet Socialist Republic of Georgia, lost patience and pulled out. AquaBounty was close to collapse before receiving a $6 million investment in 2012 from Intrexon Corp., a synthetic biology company.

Today, AquaBounty’s fish are available in Canadian grocery stores. Five tons were sold there in 2016 without being labeled as such. Canada has no law that requires labeling of genetically modified seafood.

Dawn Runighan, the facility manager, shows me the miniature tanks where the baby fish are raised, and the grow-out area where they reach maturity. There are big bags of fish feed, and canisters of sperm lined up like old-fashioned milk tanks. In another room are tubular incubators containing the eggs that will become superfish. If I was expecting a high-tech sanctum where Faustian scientists use supercomputers to meddle with the building blocks of nature, what I found was more quotidian: a few technicians in rubber boots moving equipment around and checking water levels. Much of the space in an adjoining room is taken up by an elaborate, three-phase filtration system that includes settling tanks, “bio-beads” impregnated with organisms that remove ammonia and organic matter from the water, and finally a UV-light filter to finish the cleansing process. “It’s basically a wastewater treatment plant, with fish,” cracks Runighan.

Upstairs there is a lab where quality control and R&D on the company’s proprietary gene technology takes place. A white-coated technician dips a pipette and fills tiny tubes in a rack. These will go into a machine that multiplies copies of a specific sequence of DNA for later analysis. No actual gene-splicing goes on at Bay Fortune. In fact, none has gone on for 13 generations of AquaBounty salmon, dating back to a single ancestor fish that reproduced and died in 1992. Each descendant carries a copy of the genetic construct that combines the Chinook growth hormone gene with the promoter gene from the ocean pout.

After a period of incubation at the Bay Fortune hatchery, the sterile, all-female transgenic embryos are then flown to a rearing facility in the highlands of Panama, where the resulting salmon are grown to maturity before being re-imported into Canada. (According to Conley, Panama was selected because the president of the company at the time had contacts there and the cost of building a facility was far less than it would have been in North America.) Eventually, AquaBounty plans to produce market-ready fish at a new facility now under construction at Rollo Bay, on Prince Edward Island, and at the Indiana facility—an existing fish production factory that belonged to a now-defunct aquaculture company.

The key fact about all of these places, existing and under construction, is their location: They’re on land. Nearly all other aquaculture takes place in ponds, lakes, or the sea—in pens designed to keep farmed fish in and wild fish out. Unlike fish produced using this conventional approach, AquaBounty salmon have no chance of escaping into wild habitats. That was key to the company’s application for approval by the FDA. But land-based aquaculture is expensive, and many previous attempts have failed. Finding cost-efficient ways to maintain water temperature and quality at levels needed to grow healthy fish—things nature does for free—is critical to AquaBounty’s business success.

“We saw the convergence of these two technologies: the improved biology of the fish, and the improved technology of contained aquaculture systems,” says Stotish, a former pharmaceutical executive. He says the company has “altered the economics of growth and production.”

Most scientists who have studied the matter concur—and believe that the significance of AquaBounty salmon extends far beyond the fishing industry. A 1992 article in Nature Biotechnology by Fletcher, Hew, and five other scientists laid out the evidence behind the company’s claims, and since then those claims have been validated by a number of other studies. An article published in the journal Aquaculture in 2013 (by seven scientists independent of the company) concluded that transgenic AquAdvantage salmon had higher feed-conversion ratios, retained nitrogen more efficiently, and achieved their target weight 40 percent faster than conventional Atlantic salmon fed the same diet.

“In 20 or 25 years we’re all going to be eating genetically modified animal products,” says Eric Hallerman, a professor of marine biology at Virginia Tech who served on an expert panel that reviewed AquaBounty’s technology for the FDA application. “What’ll make it attractive to producers is the benefit to consumers.”

That potential benefit has not allayed the concerns of the vocal movement opposed to GMOs in general and to genetically engineered “Frankenfish” in particular.

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Humans have been consuming salmon virtually since we first arrived in North America, and salmon have become deeply intertwined with both the cultures and the ecosystems of the places where they thrived. Indeed, salmon in many ways shaped both the civilization and the environment of those places. And salmon have been an intensely managed food source all along.

“The anadromous fish resource was perhaps the most intensely managed and ecologically manipulated food resource among these aboriginal societies,” wrote the anthropologists Sean Swezey and Robert Heizer in a 1977 study.

“Ecological manipulation” is a good description of today’s salmon market. Even the wild salmon fishery of Alaska is helped along by human intervention: Each year the Alaska Department of Fish and Game releases nearly 2 billion juvenile salmon spawned in hatcheries into the waters of Prince William Sound and Southeast Alaska. In 2015 Alaskan fishermen caught 93 million hatchery-born salmon, more than one-third of the total harvest of 263 million. Salmon stocks in the northern Pacific have recovered since bottoming out in the 1970s; that would not have happened without the coastal hatcheries.

U.S. imports of salmon totaled 339,000 metric tons in 2016, worth more than $3 billion. The vast majority of that came from farmed Atlantic salmon raised in floating cages off the coasts of Canada, Chile, Norway, and Scotland, and flown into the U.S. According to SINTEF, an independent research institute in Norway, accounting for feed, aquaculture, and energy to freeze and transport the fish, 1 kilogram of farmed salmon eaten in Paris or New York produces the equivalent of 2.9 kilograms of CO2 emitted into the atmosphere. A 2016 paper in Aquaculture Engineering found that the carbon footprint of salmon produced in land-based closed systems, like AquaBounty’s, is less than half of that from salmon produced in conventional fish farms in Norway and delivered to the U.S. by air.

In July 2016, the Quinault Indian Nation joined a lawsuit put forth by environmental groups and recreational fishermen in March of that same year. It challenged the FDA approval, saying the agency “has not adequately assessed the full range of potentially significant environmental and ecological effects presented by the AquaBounty application.” That lawsuit is still pending. Led by the Center for Food Safety, anti-GMO activists are concerned that GE salmon could threaten native species if some fish Houdini escaped and spread its transgenic kind in the wild.

But scientists who have followed AquaBounty’s long road to regulatory approval believe that the quarter-century process signals a flawed and politicized approval mechanism. The delay “sends the message to the rest of the world that the science-based regulatory oversight as embodied in the FDA review process is subject to political intervention,” testified the late Calestous Juma, of Harvard’s Kennedy School of Government, in a 2011 hearing before House Agriculture Committee’s Subcommittee on Rural Development, Research, Biotechnology, and Foreign Agriculture. “Furthermore, it signals to the world that the United States may cede its leadership position in the agricultural use of biotechnology.”

According to the scientific panel that reviewed the evidence submitted by AquaBounty to the FDA, the genetically engineered salmon “is as safe as food from conventional Atlantic salmon, and … there is a reasonable certainty of no harm from the consumption of food from this animal.”

The agency concluded that because AquaBounty salmon is “not materially different from other Atlantic salmon”—meaning it is nutritionally and chemically indistinguishable—no additional labeling was required.

In simple terms, Muir’s method quantifies the probability of an escaped transgenic fish interbreeding in the wild, and the level of harm it would cause if that should happen. The first part is itself the product of two factors: “the probability of the organism escaping into the wild, dispersing and becoming feral” and the ability of the new gene to spread.

If either of those terms is zero, according to the model, the risk of environmental damage from transgenic fish farming is zero. It’s a simple matter of multiplication. “If it can’t escape, then don’t worry about it,” Muir says. “Or if it escapes and then can’t proliferate, don’t worry about it.”

By raising the fish on land, in contained tanks, far from cold-water environments, AquaBounty has reduced the risk of escape to near zero (unlike conventional aquaculture, where the farmed fish can and often do escape into the wild). The second factor—the risk of an escaped fish spreading its genetic material—should also be zero, because AquaBounty produces sterile, triploid females. Even if these fish did escape, wild salmon couldn’t successfully breed with them, so they wouldn’t be able to reproduce and persist in the environment. In contrast, when a net pen containing conventional farmed salmon breaks, the escapees can overwhelm an environment with their sheer numbers, and since they’re fertile, they can interbreed and bring down the fitness of native salmon.

“In my view the risk of harm from GE salmon as developed and managed by AquaBounty is less than that of farmed salmon,” says Muir, who is now retired.

Alison Van Eenennaam, an animal genomics and biotechnology specialist at the University of California, Davis, who served as a subject matter expert for the scientific panel that evaluated AquaBounty’s FDA application, says that conventional farmed fish carry different, and arguably higher, risks. “Conventionally bred Atlantic salmon undergo no food safety tests, grow faster as a result of selective breeding, are fertile, and are raised in ocean net pens where they can escape to the ocean and transmit/acquire diseases and parasites,” she says.

Like most scientists who have examined the matter, Hallerman dismisses the claim that GE salmon pose a threat to existing fisheries. “This technology has been sitting on the shelf for way too long. People want more meat and this is a way to get it to them.”

But not all scientists agree with this consensus. In 2013, after the FDA issued its draft environmental assessment of the AquaBounty breeding program, Anne Kapuscinski, a professor of sustainability science at Dartmouth College, and Fredrik Sundström, an assistant professor of ecology and genetics at Uppsala University in Sweden, submitted comments criticizing the agency’s finding of “no significant impact.”

“The future of GE fish farming will surely involve larger fish farms, with less confinement, in many different environments,” wrote Kapuscinski and George Leonard, the chief scientist at the Ocean Conservancy, in a 2015 opinion piece. The risks posed by those hypothetical future farms are harder to determine.

Meanwhile, Murkowski, whose legislation is at this point the only remaining legal obstacle for AquaBounty in the U.S., has said allowing GE salmon would amount to “messing with nature’s perfect brain food.” In July 2017, vowing to continue her “years-long fight against ‘Frankenfish,’” Murkowski introduced the Genetically Engineered Salmon Labeling Act, which would not only require plain-English labels for GE salmon but would mandate a review of the FDA’s procedures for approving AquaBounty’s fish. AquaBounty officials say they have no problem with labeling their fish, if regulations require it; but Murkowski’s bill, co-sponsored by senators from Washington and Oregon, would effectively maintain the ban on AquaBounty salmon in the U.S. market.