Although there might be difference between a male/female gape of the same length, does it really matter? I think the collective knowledge (average or the upper size gape for each length) is more important. If one wanted to know this mouth gape size to control a species, etc, I think they would say when catfish get to this size they need to be controlled or the catfish will do so-n-so. Would we ever really say something like when males get 18" and females are 21" , do such and such ??? OR... if it is only a 12" female it should be returned but keep a 12" male... this goes against what most advise.
Like Bill mentioned, I think stomach contents along with size and gape are more important.
