My guess was also male(because he's more then twice the size of some of the other jags I bought at the same time). But I wanted to make sure he looked like a male down there. If you can't tell in the pic the tube sort of sticks out and then points backwards.
BTW I bought 5 ~1" Jags awhile ago, now this one is about 3.5", one is about 3", and the other 3 are just barly over an inch. I was guessing that the two big ones would be dominant and subdominant males, and the other three would be females. But the two big ones compleatly ignore the other three and always swim side by side. Do you think its posible that the second biggest one is a female?
I'll post a pic tonight, I'm at school right now
From the jags I have seen it looks to me like a pointed tube(male) and developig spotting(male) , females and subdominant males seem to keep the large blotches where the alphamale developes spotting. However I have only seen the small spotting on large jags - which means this one may be developing it.
IMHO it is hard to tell the sex of a fish strictly from the size - even if it is from the same hatch.
There will always be runts.
Before the disaster with the icestorm here when I lost almost all my fish , I raised some angels from one batch. I started with 16 and after a few unfortunate deaths I had several pairs. The bigger males were 7" high or so with females about 5" and there was one runt that hung in but never grew much over 2.5" along with one at 3.5".
Some others I have grown from small schools incluce JD, GT, Salvini, firemouths, discus and a few others.(also have a few young jags at present).
The firemouths and JD exhibit a big difference in growth pattern while the others stay relativley close.
My guess would be that it could have something to do with the fishes genetics and possible inbreeding as usually only the strong survive in nature while some weaker individuals are allowed to live and even breed in captivity - however that is a different discussion.