tbmanivong,
I ate a few grayling when I lived in Alaska, they had a nice flavor but were very soft. When my grandfather was young he used to catch (dip net) red horse suckers in northern Minnesota, they canned them. He said they were good, I haven't tried one. I ate plenty of carp in China, they were good, dare I say delicious. The bullheads I usually catch are pretty small so I don't mess with them. My guess is bigger ones would be tasty. I ate a some small fish (6" and caught some too) in China that looked like bullheads, they were good.
Terre