sex differences in nics

[duanes]

I've been growing out a group of half dozen Hypsophrys nicaraguensis from fry, other than size, for most of the year sexual differences have a bit ambiguous.
pic below is Jan 15

A couple of pairs have formed in the last month, and now dimorphism is quite evident.
pics from the last couple days
male, note the spots in the unpaired fins


female, here lack of spots

 

[henknaert]

Yes the sexual dimorphism in grown up nics is usually quite clear, as juveniles they can be quite hard to sex though.
Some of the fish in your photos seem to show a reddish area around the base of the pectoral fins which I have seen in my fish as well when they were juvenile. I wondered then if this was normal or caused by stress or inflammation? Anyone know?

 

[duanes]

I believe the red is simply a natural color trait of this location variant.