Here is how AquAdvantage salmon are made. Will Canadians want to make it for dinner?

“For the first time anywhere in the world, a genetically engineered animal has been approved for human consumption” announced Peter Mansbridge on CBC news on November 20. Members of society do not agree on how genetically modified fruits and vegetables should be labelled, if at all, but we are already moving on to genetically modified animals for human consumption. The AquAdvantage salmon by the US company AquaBounty can grow quicker and go to market twice as fast as regular farmed salmon using less feed. This genetically engineered salmon, whose fertilized eggs are produced at an inland facility in P.E.I, Canada and raised at a facility in Panama, has been approved by the FDA after a long 20 year wait. AquAdvantage salmon could be the first genetically engineered meat we eat but opposition to approving it in Canada shows this salmon is not yet finished swimming against the current.

How do you make an AquAdvantage salmon?

This transgenic Atlantic salmon has inserted in its DNA, the genetic code for a growth hormone from Chinook salmon to make it grow faster. The genetic code is a recipe for making a protein. The Atlantic and Chinook versions of this recipe are 90% identical and produce almost identical growth hormones.

Scientists sandwiched the DNA sequence for the growth hormone in between regulatory DNA sequences from a different gene that belongs to the ocean pout fish. Despite how this might sound, this wasn’t a mad experiment to see how many different DNA sequences they could stitch together in one fish. Regulatory sequences control how when and how much a gene is turned on. The normal regulatory sequence for the growth hormone activates the gene in response to certain environmental cues like temperature or amount of daylight but scientists wanted one that would keep the growth hormone turned on year round. Incorporating the DNA sequences of ocean pout antifreeze gene ensured the growth hormone would be turned on all the time.

Rather than being some kind of hybrid between three different fish, as the media tends to portray it, AquAdvantage is Atlantic salmon that produces a little more growth hormone because a slightly different recipe for making growth hormone was added to its ‘recipe box’ of 40,000 genes. There are likely other species of fish that naturally produce similar amounts of this growth hormone. This genetic modification is not as drastic as Bt corn, which contains a bacterial gene sequence for a toxin that kills certain insects, that corn does not normally produce. While it might be harder for the public to accept genetic engineering in animals than plants, the genetic change in AquaAdvantage salmon doesn’t make it that much different to regular salmon.

The genetic changes in the genetically engineered AquAdvantage salmon versus regular Atlantic salmon might seem even less substantial when we consider all the other technical procedures that are done to make the AquAdvantage sterile. Making fish sterile is not only in the interest of preventing contamination with wild salmon but also sterile fish don’t need to waste any energy of sexual maturation, they can use all their energy to grow.

To make them sterile, which also prevents maturation, AquaAdvantage salmon and other farmed salmon are made to contain three chromosome sets instead of the normal two. While birds and mammals cannot be triploid without deformities that are incompatible with life, fish do sometimes become triploid naturally. Recreational fishing lakes are stocked with fish that have been made triploid by using pressure or heat on the eggs.

Since triploid males can sometimes still produce sperm. Making all AquAdvantage salmon female is another safeguard. Reptiles, amphibians and fish are able to sometimes reproduce without contribution from a male. Unfertilized eggs can be triggered to develop into embryos that contain only DNA from the mother, a process called gynogenesis. To make AquAdvantage salmon, transgenic salmon eggs are first treated with Arctic Charr sperm in which the DNA has been destroyed by irradiation. This tricks the eggs into thinking they were fertilized even though they didn’t get any paternal DNA. To produce an egg, cells split their chromosomes from diploid (2 matching sets) to one haploid set for the egg and one haploid set to be discarded. Normally fertilization by sperm carrying its own haploid set brings the egg back to its diploid status and embryonic development ensues. Applying pressure on the eggs causes the other haploid set to be retained making a diploid egg that develops into a fish with only its mother’s genetic material. Gynogenesis is no longer part of the process since AquaBounty now maintains a stock of transgenic diploid breeding of females.

Okay so now we have diploid females with two copies of the transgene, but AquAdvantage are tripoid, with one copy of the transgene. So next, the diploid females are turned into neomales by giving a hormone – no surgery required for gender reassignment in fish. These transgenic neomales mate with non-transgenic females. The pressure treatment is used again to retain that extra set of chromosomes, but this time the sperm supplies one chromosome set making three.

No foreign genes are added and they are not officially considered GMO because they are not engineered but there is a significant change to the genetic material that does affect the health and growth of salmon. Triploid salmon have fewer cells but they are larger, causing an increased oxygen demand, due to the change in surface area to volume. In some countries farmed triploid salmon are used but it has not been widely adopted because they do not grow and perform as well as diploid fish. Growth hormone transgenic salmon that are triploid do not grow as fast as their diploid counterparts but grow faster than non-transgenic salmon. Triploidy does not appear to affect meat quality as much as the season and body size of the salmon.

Reactions to FDA approval

Head of Ocean Sciences Department at Memorial University, Garth Fletcher told The Star he was happy to see his creation get approved as he didn’t think approval would happen in his lifetime. Fletcher is no longer involved with AquaBounty but began working on this growth improved transgenic fish with other scientists back in 1982. On CBC news he said “the risk is as minimal as you could ever expect to get with any product.”

While the salmon is not approved in Canada for human consumption, some grocery store chains have already boycotted AquAdvantage salmon. The first step, the production of eggs in P.E.I has been approved by the federal government. Now there is a court battle with British Columbia’s Living Oceans Society and Nova Scotia’s Ecology Action Centre together challenging the federal government’s approval. They are concerned AquAdvantage salmon would be toxic to the environment as an invasive species if they were to escape and that this was not adequately assessed. Secondly they argue that Environment Canada had a duty to inform the public but failed to do so.

Natalie Huneault at Environment Canada told the National Oberver, “there were no concerns identified to the environment or to the indirect health of Canadians due to the contained production of these GM fish eggs for export.”

Anastasia Bodnar over on Biology Fortified does an excellent job of going through the risks and mitigation of AquAdvantage salmon (here and here) both with respect to safety of eating this meat product as well as in preventing escapee transgenic fish from contaminating wild salmon populations. The Fisheries and Oceans Canada document containing assessment of risks to the environment and health are found here. Due to the containment facility and procedures there is extremely low likelihood that any fertile genetically modified salmon would escape to an area where it could survive and reproduce.

The failure of Environment Canada to properly inform and have a discussion with the public before approving the P.E.I fertilized egg production facility will certainly have increased public mistrust and fear of this genetically engineered salmon. I think that if the public feel that this step has already taken place behind their back, future discussion about approving genetically engineered salmon as safe to eat, is only going to be met with suspicion.

The FDA will not require labelling of the genetically engineered fish. So any consumers afraid of eating the fish or opposed to the generation of these fish might buy more wild salmon. Ironically such an increase in demand might be a greater threat to the wild salmon than the risk of escaped genetically modified salmon.

While I don’t feel I would be risking my health eating AquAdvantage salmon, I am not sure I would choose it in a supermarket over other farmed salmon. I find genetically engineered triploid salmon fascinating….but not so appetizing. I think a similar gut reaction in consumers is the biggest hurdle for genetically engineered foods. There needs to be a good reason to choose genetically modified foods over the alternatives. If AquAdvantage salmon production can be shown to be better for the environment than other farmed fish people might try it and eventually not be turned off by how it was made.

References:

Benfey, T. Use of sterile triploid Atlantic salmon (Salmo salar L.) for aquaculture in New Brunswick, Canada. ICES Journal of Marine Science, 525-529.

"Canadian Aquaculture R&D Review 2015." Government of Canada, Fisheries and Oceans Canada, Communications Branch. Web. 3 Dec. 2015.

"Canadian Scientist Thrilled to the Gills by U.S. Approval of Genetically Modified Salmon | Toronto Star." Thestar.com. Web. 3 Dec. 2015.

"Court Battle Begins over AquAdvantage Salmon, World's First Genetically Modified Food Animal." National Observer. 17 Nov. 2015. Web. 3 Dec. 2015.

"An Overview of Atlantic Salmon, Its Natural History, Aquaculture, and Genetic Engineering." An Overview of Atlantic Salmon, Its Natural History, Aquaculture, and Genetic Engineering. Web. 3 Dec. 2015.

"Genetically-modified Salmon Production Appealed to Federal Court - Prince Edward Island - CBC News." CBCnews. CBC/Radio Canada, 16 Nov. 2015. Web. 3 Dec. 2015.

"Information on Genetically Engineered Salmonids." White Paper by the Association of Fish and Wildlife Agencies. Dec. 2012.

"Preventing Escape of GMO Salmon"  Biology Fortified Inc. 20 Nov. 2015. Web. 3 Dec. 2015.

"Risk assessment and mitigation of AquAdvantage salmon"  Biology Fortified, Inc. 16 Oct. 2010.

Summary of the Environmental and Indirect Human Health Risk Assessment of AquAdvantage Salmon - Fisheries and Oceans Canada - Science Response. 2013.

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