It doesn’t happen often in nature, but now and then, a wild Atlantic salmon (yes, there are still a few left) mates with a brown trout and has hybrid offspring.

This ability to reproduce between species had some Canadian scientists curious: If a genetically modified Atlantic salmon were to come in contact with a brown trout, would it too be able to have little transgenes babies? The answer is yes, according to a new study published in the Proceedings of the Royal Society B. And it turns out that those offspring carry the genetically inserted trait that allows them to grow faster than their Mother-Nature-made cousins. Much faster. In fact, the hybrid offspring outgrew their genetically tweaked parents as well.

‘When the fish were placed in a mocked-up stream inside the laboratory, the researchers found that the hybrids were out-competing both the genetically modified salmon and wild salmon, significantly stunting their growth,