杏吧原创

If the US approves genetically modified fish for human consumption, the implications will be global

AT AN undisclosed location in the highlands of Panama, 68 water tanks sit behind a code-protected door. The building鈥檚 ground-floor windows are barred, motion detectors are deployed inside and the exterior steel doors are dead-bolted. To reach this citadel, an intruder would have to breach a fence topped with barbed wire and dodge motion-activated cameras.

What sounds like the lair of a James Bond villain is actually a fish-rearing facility owned by , based in Waltham, Massachusetts. It was set up to win the world鈥檚 first approval to sell a genetically modified (GM) fish for human consumption. Whether or not the safety measures are sufficient will be debated next week, when the US Food and Drug Administration (FDA) holds on AquaBounty鈥檚 to sell a variety of Atlantic salmon that is .

Regulators worldwide have been looking to the FDA to take a lead on the issue of GM fish. If, as seems likely, it gives the green light, engineered fish being developed in labs from China to Cuba could follow (see table). 鈥淭his is precedent-setting, not just in the US but internationally,鈥� says , a fish geneticist at the Virginia Polytechnic Institute and State University in Blacksburg.

AquaBounty鈥檚 salmon owes its rapid growth to . It would be the first GM animal to be approved for human consumption. The main scientific controversy relates not to the safety of eating its flesh, which was given a clean bill of health by the FDA鈥檚 scientists. At issue are the potential ecological consequences should fish escape.

鈥淭he salmon would be the first GM animal of any type to be approved for human consumption鈥�

Farmed fish can wreak havoc if they get into the wild. Large numbers of Atlantic salmon have escaped and are breeding with their wild cousins, producing animals that are less likely to survive. Farmed Atlantic salmon have also escaped into Pacific waters, and there are fears that they may compete with native species of salmon.

Add genes from other species into the mix, and the potential risks become even greater, which explains why AquaBounty has faced formidable hurdles in bringing its salmon to market. The original plan, hatched more than a decade ago, was to grow the fish in conventional salmon farms, using net pens in coastal waters. The risks of escape were deemed unacceptable.

That led to the company鈥檚 current proposal. It states that the salmon will be produced in secure, land-based facilities. Fish will be hatched and grown in Panama, where Atlantic salmon would be unlikely to survive even if they did somehow escape. All-female eggs will be flown in from a similarly contained facility on Prince Edward Island in Canada. Shortly after fertilisation the eggs will be subjected to high pressure, which makes them retain a set of chromosomes that is normally expelled, resulting in sterile 鈥渢riploid鈥� fish. 鈥淎quaBounty has gone to unprecedented lengths to provide a product that can address people鈥檚 concerns,鈥� argues , the company鈥檚 president.

Ecological risk-assessment experts agree that the measures are impressive. But AquaBounty鈥檚 set-up will be just the beginning of the GM fish market. If it is to turn a profit, it will have to sell eggs to other salmon producers, who will need their own facilities. Without knowing their locations and precise safety measures, it鈥檚 hard to judge the likelihood of fish making it into the wild, says of Dartmouth College in Hanover, New Hampshire, who studies the risks posed by GM fish.

Should any fish escape and survive, the risks are uncertain. Hallerman鈥檚 team has found that AquaBounty鈥檚 salmon seem more susceptible to stresses including extremes of temperature and shortages of food. While that suggests that they may struggle in the wild, work on GM by of Fisheries and Oceans Canada in Vancouver and Fredrik Sundstr枚m of the University of Gothenburg in Sweden has shown that the consequences of carrying a foreign growth-hormone gene can vary.

For example, raised in a typical hatchery environment, the GM coho salmon grew bigger, were more voracious predators and took risks that could expose them to being eaten if they were in the wild. But when raised in a simulated natural stream, these differences were much reduced. This makes it difficult to calculate the risks posed by GM fish. 鈥淚f the environment changes you don鈥檛 know how they will respond,鈥� Sundstr枚m warns.

What鈥檚 more, AquaBounty鈥檚 system for producing sterile fish is only about 98 per cent reliable, so there is a small chance of escapees breeding with wild fish. That is a concern, given the 鈥淭rojan gene鈥� hypothesis, which states that a gene which boosts reproductive success but is ultimately harmful to the species can rapidly spread through a wild population if just a few genetically modified fish escape. Studies simulating natural populations suggest that this could cause them to crash.

Beyond the questions surrounding AquaBounty鈥檚 salmon is the precedent that would be set if it is approved for sale. Many more GM fish are being developed in the US and beyond. of Auburn University in Alabama is developing GM that grow more quickly or resist bacterial diseases (see table). He is still perfecting techniques to ensure sterility, by knocking out genes vital for reproduction, but he hopes to bring the fish to market within three or four years. FDA approval for AquaBounty鈥檚 fish would be a significant step towards making that happen, he says.

Others are itching to move straight away. of the Chinese Academy of Sciences鈥� Institute of Hydrobiology in Wuhan has developed a growth-enhanced that he says has been ready to market for a decade, held back only by regulatory concerns in China. FDA approval of AquaBounty鈥檚 salmon would improve the prospects for Chinese GM fish, says Zhu. If that happens his team will 鈥渄efinitely鈥� make an application to the Chinese authorities.

China accounts for about half of the world鈥檚 aquaculture, so any approval could open up an enormous market 鈥� and raise significant questions about how to prevent escapes. As Kapuscinski puts it: 鈥淚t seems to me that achieving multiple confinement, and assuring it, would be very challenging in China.鈥�