In northern ca? Fish, barnacles, crabs, various mollusks. It’s the other three that initially attract the fish, so they do occasionally catch things casting off of a pier, I think. I wish I knew which kinds of fish offhand. In fact, judging by the size of the hooks I’ve seen used, they can catch some reasonably large fish.
I *think* they can “sit”, but it’s not a relaxed position for them.