I bring this up only to say it is a GOOD thing that you have other types of shiners in addition to having GSH. If you can arrange for your larger fish to eat the larger GSH (before they get too big) then some of the potential negatives go away. If the GSH get beyond the gape size of your predator fish then comes possible issues where the very large GSH eat a lot of young fry and other things and then they do not have their own predator anymore.
The emeralds and common shiners offer the advantage of diversity and perhaps they will also offer an advantage in continuing to reproduce for more years than the GSH.
I don't know if common and emerald shiners need crevices to spawn but if you can create the proper spawning conditions for the various kinds of shiners you can also encourage their survival.
