If the river has some deep spots, structure/cover (like rocks/rip rap) and also has carp in it, then I would suspect that there are also bass present. Have you walked around shore to check if there are empty bags of plastic worms, or discarded packages for hooks, spinnerbaits etc, stuff one would use for bass? That, besides other bass fishermen, is always a pretty good indication.

I’m having trouble understanding trout and the river tarpon in same water. Thought the river tarpon were only in lower stretches of rivers here. Trout unless in a stocked pond are mostly in small streams in mountains or maybe below dams in some places.

What water were you fishing? Steve, Rob, Nomad big trout jumping around in a Korean body of water?

To answer your question on the bass, they are usually in slow moving or still water around cover rather than in the river current. But Stever and Nomad can give much better info than me.