Hi Guys,
Thanks for taking interest in my article.
Just a couple of points to clear up. The article only discusses both melanura/synspila populations and not any other fishes assigned to the same group, so I can't say for sure if they display similar sexual traits regarding eye colour. We can always sex fish by morphology observations, such as flowing unpaired fins, cranial profiles, colour, venting etc....
The eye colour is only displayed when both fish are showing dominance or sexually active (pre-spawning behaviour). This doesn't mean sexually mature. I doubt you will notice this eye colour by just keeping single sexually mature specimens?
Just a couple of photo examples to give a better idea of my point, both photos show pre-spawning fish.
Vieja melanura (synspila) pink headed morph
Vieja melanura, orange morph, male and two females.
Cheers,
Lee.