I made a deliberate effort to purchase fish off the fish truck rather than the hatchery, last year. No unwanted hitchhikers at all. Course' I was purchasing HBG in the first place, so my idea of a trash fish would've been a HSB or perhaps a stray WE or two........no such luck.

But more to the point, there weren't any FHM or BH in the mix either. This particular truck is operated by a hatchery right here in state, and they claim to raise their own fish. At least that's the case for the HBG I purchased, anyway.
Perhaps all companies running fish trucks are not cast from the same mold.