Transgenic salmon hybridize with trout, produce sterile offspring

Baby brown trout (CREDIT: Zouavman Le Zouave, Wikimedia Commons).

Researchers in Canada recently confirmed that AquaBounty’s genetically modified Atlantic salmon is able to cross-breed with unmodified brown trout populations, producing viable offspring that grow at an accelerated rate like their transgenic parents. What some of the coverage forgot to note was that the offspring of brown trout and Atlantic salmon (which hybridize naturally) are sterile. Yes, these transgenic salmon could create hybrid offspring with wild fish, but these hybrids would be unable to reproduce.

Furthermore, the specific salmon used were fertile, for research purposes, whereas the fish AquaBounty intends to market would all be sterile females with a third set of chromosomes to effectively eliminate the prospect of them breeding in the wild. And they would be stored under lock-and-key far away from oceans or brown trout populations.

The most frightening ecological bugbear plaguing the development and agonizingly slow approval process of AquaBounty’s fast-growing, genetically modified AquAdvatange salmon is the “What if it go out?” scenario. It’s a scenario that should be evaluated with every transgenic animal. However, the only thing this study proved is that if you try, under laboratory conditions, to breed AquAdvantage salmon with brown trout, you can. This was intentionally a “worst-case scenario” experiment.

The fearful response to this study—Frankensalmon could breed with trout, produce frankentrout,” says Grist—ignores  a mass of important context and assumes that all of AquaBounty and the FDAs fail-safes and safety measures are worth nothing. Traditional fish-farming runs the ecological risk of farmed species getting into local bodies of water and wreaking havoc, but it is not under the same scrutiny (and apparent suspicion) of efforts to farm GM salmon.

If we’re going to have an intelligent conversation about the risks posed (and not posed) by the AquAdvantage salmon, we must take into account the safety measures that will be employed by the company producing the salmon—all of which were intentionally bypassed in this study to test the hypothetical scenario of fertile AquAdvantage salmon breeding with brown trout.

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  • Time and time again we learn that fail-safes and safety measures are worth precisely nothing.

    People make errors in designing systems – such as the design of the vessels in the Fukushima nuclear power plant where the holes for the graphite rods were at the base of the vessel. No one envisaged the graphite melting, but it did.

    There is human error such as the decision by the supervisor in Chernobyl to run the test against the advice of those under him.

    There is human greed, lack of care, and taking shortcuts – too numerous to mention, but the Deepwater Horizon well in the Gulf of Mexico comes to mind.

    The real measure of risk is surely to say that sometimes, when the consequences of the thing guarded against coming to fruition are huge – then just don’t do it.

    • Chris

      Read up on some developmental biology before you compare melting graphite to the inability to produce viable offspring.

      • That’s too vague for me. What do you mean to say?

        • Chris

          I mean to say that you should look at the conditions required for successful cell division before stating that human intervention will subvert its requirements for effective prevention of species interbreeding. The presence of the third set of chromosomes will cause them to not align properly along the spindle during meiosis and thus deposit fractured remnants in any resulting daughter cells. These segments will play havoc with early development and prevent it from dividing beyond the first few cells. Man isn’t orchestrating a new, untested failsafe for these fish; it’s utilizing an existing mechanism.

          • Hi Chris,
            I haven’t forgotten this – I will make time to do so in the next few days.

          • Nigel

            Unless these fish were suddenly able to grow legs, they probably cannot escape. I’m curious whether they taste more like salmon, or trout? What is the fatty-acid profile of the fish? From my own experience, farm raised salmon lacks the higher omega content, and colour is less appealing than wild to may consumers. If the diet of the new breed was of better quality, these fish may be tastier, and indeed healthier than their farm-raised orange cousins!

  • Fred

    Did the original paper ever state that the hybrids were sterile? Or is this just the author’s assumption that because non-GM salmon and trout produce non-fertile offspring, the same must be true for the GM-cross?

    • Carver

      Yes, original paper stated that the fish would be all female triploid organisms. Trying to breed with that extra set of chromosomes makes any eggs that manage to be fertilized (unlikely as that may be) replicate and divide their DNA unevenly during mitosis, resulting in fatality before it’s gone through more than 1 cell division.