I don't think the city has ever put Koi in Hickory
I think they are pets that have gotten too big and has been turned loose. I've seen goldfish in there occasionally as well. And somebody found an iguana a year or so ago.
Ahhh those crazy Islanders!
No I have never fished for them in Shoal. I thought about it many many times though.
I'm not sure how you do it,you may be going to do it on the fly, but I like to bait up a hole in catch them on doughbait with a rod and reel.
Which you could still bait the hole and then use the fly rod.
If you do that I would bait the bottom end of the riffle. It will draw every one of them up out of that long pool.