Bassmaniac,
I am simply saying that some people will trap there own minnows in ponds or creeks nearby to use for bait. 99% of the time they are using fathead minnows, but sometimes other species such as suckers, carp minnows and shad minnows can be mixed in, even if it is only 1 or 2 out of 2 dozen.

I have personally found shad minnows, suckers, carp, and even a pickeral in my bucket that I have purchased from bait stores, so it does happen and the novice fishenman that goes once or twice a year does not know the difference. And often times when they are done fishing they dump the minnow bucket in the lake, even though we know you are not supposed to.

Furthermore, I believe it is illegal to intentionally use LIVE shad as bait in Indiana anyway, so even if you used a casting net to catch them it would be illegal to use them for bait.(while alive)