GM salmon and wild brown trout can interbreed

Brown trout and Atlantic salmon are known to interbreed in the wild and produce hybrid offspring (a 2005 study found that 18.48% of juvenile Atlantic salmon in a Lake District stream were trout/​salmon hybrids.) 

A study has just been published demonstrating that genetically modified salmon can breed with wild brown trout, passing on their GM genes. They also produced faster growing hybrids that out-competed wild salmon, albeit in a laboratory environment. To read the study, click the link below:

Oke et al, 2013