i found these really cool and acurate artist renderings of a blue, a channel and a bullhead. they should help with identification issues. i would like to have got them all on the same page but i don't know how. also, i found out earlier while reading my field guide to north american fish another way to tell channels from blues. the posterior end of the adipose fin( the little nub on the cats back past the dorsal) is absent in blues. it has one but not as as protruding as channels. kind of like how some people have big earlobs and some people dont hardly have any. just thought i would pass that along.