I think mine looks almost exactly like the one on the left in inchworm's link it says Co.agassizii...... I think it's that one, but it looks almost identicle to the one on the left
Yeah, in looking again, I'm leaning away from leucomelas b/c there's just a little bit of black on the dorsal fin. Delphax or agassizii would be more like it.
The best way to distinguish male from female is to look at a whole group of the same age. The females will be larger and fatter - especially when viewed from above.