If you Google Redhorse Minnow you will see that there are several different species that have that nickname. So If you could find a picture of what you are looking for you could probably find out what you want to know. But I am guessing the operative work here is "minnow". Unless you can find it on the endangered list it is probably legal bait.
I catch Redfin Shiners often, and they make good bait.http://126.96.36.199/JonahSite/piclumbratilcrail01.htm
Legal bait according to:http://www.tpwd.state.tx.us/huntwild/wi ... finshiner/