At my local river almost all of the smallmouth have a gash in the middle of there jaw, any reason for this? it makes them hard to lip sometimes.

It's probably from chasing crawls/bait in the rocks on the bottom. I have had a lot of smallies dive to the bottom rubbing the bottom to get rid of a bait once hooked. 

so would using a tube be a good option for these fish?

Tubes are always a good option when fishing for smallmouths in a river. 

Do you think you could post a pic sometime of this? Just curious as to what this looks like. Thanks. 

Yea im going today, if I catch one I'll post it

Basically the hard part/ bone of there jaw is cut and there jaw looks like this \/ pretend that's the jaw and right at the point there's a cut