A fine kettle of fish fearmongering

Consumers continue to demand fish at very high levels, and this puts pressure on wild fish stocks. A report recently highlighted the fact that aquaculture is becoming increasingly important:

If we continue to fish at the current pace, some scientists predict we’ll be facing oceans devoid of edible marine creatures by 2050.
Aquaculture could come to the rescue. The Food and Agriculture Organization of the United Nations predicts that farmed fish will soon surpass wild-caught; by 2030, aquaculture may produce more than 60 percent of fish we consume as food.

There are several ways GMOs could help keep us from overfishing while still supplying sufficient resources to salmon-eating humans and their pets. One company is using GMO yeast to feed salmon. Another effort is being undertaken to have plants provide the necessary oils for the fish. Both of these strategies help to reduce the need for smaller feeder fish for the salmon. Another way to reduce the resources required for fish farming is to have the fish grow faster. They convert feed faster, and don’t need to be in tanks or pens for as long a period of time. This could be from conventional breeding [PDF], or it could be from GMO fish, as AquaBounty has done. And the AquaBounty strategy also includes having the fish grown only in inland recirculated tank systems–which the Monterey Bay Seafood Watch team has scored as a “Best Choice” for other salmons.
BBC "Trojan gene" storyFor many years now, we’ve been awaiting the approval of the fast-growing GMO salmon. Of course, the idea of fast-growing fish has ignited fears over the years, and a great deal of ink (or electrons) have been spilled by many of the fearful. (Although I once asked this author if there was evidence of that Norwegian fast-growing salmon causing problems. I think his response means no, he has no evidence.)
Many activists cite the work of William Muir and Richard Howard, who published a research paper about the potential for some fish to become “Trojan fish” which could out-compete fish without a size advantage. The BBC covered this work in 1999, as shown in the accompanying image.
From the beginning, Muir tried to tell people that these results should be interpreted narrowly:

Muir also cautions that the results of his laboratory study should be interpreted conservatively. “The study does confirm there are significant risks to natural animal populations associated with the release of transgenic animals. We assumed a consistent environment with only one variable – sexual preference for size coupled with low life expectancy for the transgenic. The natural world is not nearly as orderly, and genetic background changes could negate the Trojan gene,” he says.

The work involved a gene that offered a mating advantage–the oversized adult growth of the fish under investigation made them popular, it seems. But–not all traits will result in the same outcome. And Muir has been trying to tell this to the activists who have been mis-using this work for all their anti-GMO claims for a long time. A recent example was here: Foes of GE salmon raise specter of ‘Trojan gene’ effect.

Not so, says the author of the Trojan Gene hypothesis, William Muir, an animal science professor at Purdue who has been yelling loudly, to little effect so far, that his work is being misrepresented by the GE salmon’s opponents.

Muir said the assumption at the time of the study in 1999 was that a GE salmon would grow faster and bigger and that its size would be an unbeatable advantage in mating.
But AquaBounty salmon don’t get any bigger than ordinary salmon, they just reach full size faster, so any size advantage they have is temporary.
More importantly, Muir said that studies show that transgenic salmon are lousy at the courtship required for mating.

Of course, the fact that Muir supports the idea that the risk of harm from the GMO salmon is low doesn’t daunt folks opposed to it. Funny how they cling to his initial work, but not what he says about the salmon that doesn’t suit their narrative.
Kettle of GMO FishMuir has continued to study the behaviors of GMO fish. Recently he and his team have produced another paper on the subject. They looked at Glofish®, which have been feared by activists of resulting in the Trojan behavior. This controversy was re-ignited a while back, as you can see from the coverage the glowing aquarium fish got from a number of outlets. Biofortified attempted to put out the flames at that time. Other outlets? Not so much. Threat. Threatens. Worries.

So thousands of shares, propagations, forum posts and comments later–people have the got the fear meme in their heads. But what was the outcome of the new work? Evolution in action: Mate competition weeds out GM fish from population.

Purdue University research found that wild-type zebrafish consistently beat out genetically modified Glofish in competition for female mates, an advantage that led to the disappearance of the transgene from the fish population over time.

Well, that’s data. And their previous model? “The study also showed the effectiveness of a model Muir developed to assess the potential risk posed to natural populations by transgenic organisms. ” Environmental activists should be comforted by the effectiveness of this model, right? They seem comfortable with the ideas and predictions of climate models.
But how did this play out in the media? How much coverage did we see on this important follow-up to the previous fears?

Um. Well, not so much. I’ve been looking, and so far only two media outlets have done the right thing in attempting to un-scare everyone. One piece from Brooks Hays with UPI: Genetically modified fish outcompeted in evolution experiment. Commenters complain about this as evidence of evolution. Heh.

wapo_glofish_2015Congrats to Chelsea Harvey and the Washington Post for being the first ones to cover this work in real depth, with much more than just the press release but other important context: No, genetically modified pet fish are not going to wreak ecological havoc. And this part–where she quotes Muir–is quite nice:

And when it comes to GMOs, looking at these kinds of evolutionary outcomes can be an effective way of approaching conversations about their safety and their environmental risks, according to Muir. “This is such a heated and charged argument and so filled with emotion that as a scientist you say, ‘Let the data speak for itself,’ ” he says.

But does the data speak for itself? The fear was pretty chatty–but the data? It’s been pretty quiet. There’s only one comment at the WaPo piece, and it was mine. But some people don’t think that evidence from evolutionary outcomes is sufficient, as we’ve seen for the recent data from sweet potato sequencing. But in the long run, it will be the data that matters. And it matters to regulators too. If we want to reduce pressures on wild fish, and reduce resources needed to feed fish fans, let’s look to the data instead of the fear.
Muir, W., & Howard, R. (1999). Possible ecological risks of transgenic organism release when transgenes affect mating success: Sexual selection and the Trojan gene hypothesis Proceedings of the National Academy of Sciences, 96 (24), 13853-13856 DOI: 10.1073/pnas.96.24.13853
Howard, R., Rohrer, K., Liu, Y., & Muir, W. (2015). Mate competition and evolutionary outcomes in genetically modified zebrafish (Danio rerio) Evolution, 69 (5), 1143-1157 DOI: 10.1111/evo.12662

Written by Mary Mangan

Mary Mangan has a PhD in cell, molecular, and developmental biology from the University of Rochester. She co-founded OpenHelix, a company that provides awareness and training on open source genomics software tools. She has published numerous articles on biology, biotechnology, biometrics, and genomics.


  1. Thanks, Mary. Well reasoned as usual. Hence this question. Concern has been raised about ocean pen farming in bays and fjords. The fish are concentrated and therefore so is the poop. how much of a problem could this be?

    1. For the non-GMO Norwegian fish, and any other conventional fish, this could be a problem. For the GMO fish from AquaBounty, it’s not at all an issue. Their approval would be specifically for only inland tank farming. There are no ocean pens.
      Another interesting item about tank farming came from this outfit in North Dakota a while ago: Fish farming finds its way to land-locked Midwest. In open pens there’s not a lot of control over microbes, but in these tanked situations:

      Land-based tank fish farming nearly eliminates fish manure runoff and water waste through use of water recirculating and treatment systems, he noted.
      “This technology lets us … raise fish in a very clean environment, very optimized for their health,” said Steven Summerfelt, who is the director of The Conservation Fund’s Freshwater Institute in West Virginia. “It’s free from disease. We haven’t used antibiotics, pesticides, anything, to treat the water or the fish for over a decade, because we keep the diseases out.”

      Another case of reducing antibiotics, pesticides, and runoff with technology. They should do more of this for the conventional fish farming too.

  2. Tank fish farming research incorprating GE seems very good to do compared to ocean near-shore wild environments, where adverse effects if any could not necessarily be controlled as easily. As long as we don’t make the fish pesticide resistant for starters.

  3. Eric
    When fish farms were first started in the mid 80’s it was thought shallow inlets were the ideal sites. Science proved that to be incorrect. Now deep water siting is the norm and with reasonable flow rates benthic impact below fish farms has been greatly reduced. Unfortunately politics is holding up the moving of the last few shallow water sites on the BC coast.

  4. I am fish farmer. your writing is abit technical. But I always learn Something from your articles maryM. Good work.

  5. For one thing; I would counter that consumers are not just demanding fish in high quantities; they are demanding large, carnivorous, unsustainably fished species (tuna, salmon, swordfish), whose fishing practices threaten them and other species with extinction. Were we to develop a taste for sustainable species like mackerel, snapper, and octupus, there would be no need for a discussion around “designer” fish. If countries like Japan were sanctioned for their terrible practices with sharks and for their lust for tuna, there would be enough to go around. Humankind has always been good at engineering their own destruction, which includes the destruction of our food supplies. Remember that science is always shifting, and just because we can do something, it doesn’t mean that we should.

    1. Citation needed. How do you know there would be enough fish for everyone if said sanctions were put in place? Is Japan holding the entire world’s fisheries down?
      Logical fallacy detected. No one is saying that just because something can be done that it must be done. But people are saying that if there is a need then there is a compelling reason.
      You are asking for a cultural change with fish eating preferences to solve the problem. That’s fine, but I lack the confidence that you have that this would work in practice. But we can easily see how a technological intervention can have an expected impact.

Comments are closed.