Many different species of shiners, and even several different families.

Have you identified the type of shiner?

I posted a thread question about using the shiners and other "minnows" native to my creek in my ponds. Most of the people said that switching fish that prefer a certain environment such as a creek would probably have a tougher time in a pond.

OTOH, they said it certainly wouldn't hurt to experiment with a species that has a very low chance of overpopulating in a pond. The only price of failure would be the effort to catch and transport the shiners.

If you can't find shiners from a fish supplier, do you have any buddies in the area with shiners in their ponds? I would minnow trap some of those to identify. Then if you need more, ask if you guys could do some limited seining.

However, from reading on the forum, the local fish suppliers generally stock species that perform well in the region in the typical pond. Although perhaps there are a few species that are good for ponds, but they don't stock because they can't make a profit for whatever reason.

If you are talking about golden shiners, then there are lots of threads on Pond Boss to read.

P.S. Are you going to add fathead minnows to the pond to jumpstart the re-stocking project? If so, do any suppliers also carry gambusia (mosquitofish)? There are some owners on Pond Boss that stocked both types and still have gambusia in their ponds long after the predators have cleaned out the FHMs. I think this is more likely in a pond with decent weed cover.

Good luck helping your buddy get his pond back in shape!