Don't go by a black spot on the Gill plate but by the Black spot or blotch on the dorsal fin. The Gill plate is VERY inaccurate because Males get them too. But if there is a black blotch on the dorsal fin than it would be Female.
Based on my experiences with keeping and breeding sals, the fish in question appears to be male.
In my experience, males have always lacked a dorsal fin blotch.
In my experience, males have lacked a dark gill-plate blotch, but have oftentimes had a red gill-plate blotch (or no gill-plate blotch at all).
In my experience, males have had the darker red---more present in 'rows'---on the belly.
In my experience, males have possessed more blue spangling on the body than females.
In my experience, males have always had a less vibrant yellow base coloration to them than females.
Individually, many of these may be considered inaccurate/unreliable ways of sexing.
That is why I always look for a combination of these factors when attempting to sex salvinis.