Nice RES. By Shorty's observations of the fin length in relation to the urogenital opening, looks like a female.
I was thinking male based on the urogenital opening and the brighter colored ear tab. Pelvic fin length seems to vary a little bit between individuals and quite a bit based on body condition. Pelvic fin length is possible indicator of male and female RES, but I would not consider it a very reliable one on its own. When sexing RES look at the whole picture, eartab, urogenital opening, pelvic fin length, and see if everything lines up as male or female like it should.
