The top mouth gudgeon shouldn't have survived in the wild but it has and decimated the natural population of fishes in quite a few tarn's in the Lake District, their numbers have gotten so bad that some of the tarn's have been poisoned to try and get rid of the fish
I may be wrong but certain parts of China have pretty cold winters similar to ours or worse so in theory some of these species could survive and establish them selves, although like Mick said I think a lot of it has to do with the risk of introducing disease's or foreign bodies to waters.
Pardon my honesty - I am a Northerner
14 loach species bred, which will be next?