Male nics have Black or grey spotting on the dorsal..
Female JD's have a more Oval shape and More splotchy gill plates that the blue spltching most of the tiem runs all the way under neath the jaw. As well and the Females usually carry a lower spotting.
Where as the Male carry a higher spotting on the body level as well as more literal spots (circles) rather than splotches that the female has.