I have catch several on dropper nymph type flies when bream fishing. I don't know if they are any spookier than any other fish really however, we tend to see them in shallow water, I have seen them extend their entire head out of the water to get grass off the bank. They do get large, the first I ever heard of anyone catching was back in MS in a state park lake, it weighed 58 lbs. the guy catch it fishing a plastic worm and wanted it certified as a record catch, at the time the state of MS did not consider it a game fish and did not maintain a record for grass carp.

I landed a 7.5 lb. on a 3 wt. several years ago with a 4 lb. tippet, it was fun for several minutes.