A recent question we were asking has been, how to identify a male or female Carp?
I started to investigate the question and found a few links/ websites and resources which seem to contradict themselves, one states:
The identification of the male and female of Common Carp is not difficult, if it is practiced. Generally at the early stage of its maturation the fish show orange coloration on the lower portion of caudal fin and anal fin (shown right top). The coloration turns deep and deeper as it proceeds to maturation.
The male Common Carp is generally identified with its elongated body (shown above), as compared to the female. The male is further confirmed by its genital opening in concave form.
Afterwards the development of gonad advances, so the other characteristic becomes more and more distinct and identification get's easier. With the development, the male fish's operculum and the pectoral fin's upper surface develop some tubercles and turns rough in compare to the female. Moreover, the mature male oozes out white milt from its genital opening on even slight pressure of abdomen.
Similarly, the female possess genital opening with convex surface. As it matures, the female becomes easier to identify by its swollen belly. At this stage, its genital opening bulges out and forms distinct convex surface. It even protrudes bunch of eggs even on slight pressure on belly. Source01:
The second resource stated:
Cyprinids, Barbs and other members of the cyprinid family are rather difficult to sex. Differences will vary by species, but generally males are more intensely colored and slimmer than females. Source02: