I have a lot of experience working with fish (I am a Fish technician at South Dakota State University). I just thought I'd throw in my two cents. It is next to impossible to sex centrarchids outside of the spawn, and during the spawn I don't think there are many very good ways to sex fish unless you can see the eggs, or the fish are spewing eggs or sperm out of the urogenital opening. Visual and physical cues can give you an okay idea towards gender, but I don't think that using just these to determine fish gender will give you 100% success.
