Offering this as a question.
I used to bullhead fish with my grandfather and one of his old buddies in an awesome pond. We caught all three of the bullhead species. The yellow bullheads were obvious.
The coloring of the other bullheads WAS NOT binary, but showed a fairly broad range. The old buddy told me (8-10 y.o.) that the black bullheads had jet black whiskers and the brown bullheads had dark whiskers.
As we compared them on that basis, the shapes of the fish seemed to split fairly well into two distinct categories. (I am assuming black bullheads and brown bullheads.)
I DO NOT know if that is a valid indicator to distinguish between black and brown bullheads. Further, I don't know if he knew the other indicators such as anal rays, etc. and was just dumbing it down for a kid - but his identifications were accurate?
If anyone does know, then I would appreciate a comment. My recollection from childhood is that it was fairly easy to see a distinct color difference on the whiskers, especially if you started the day holding a black in one hand and a brown in the other.
