How do you sex yellow labs?

[ManannanMacLir]

I recently put two yellow labs in my 55 gallon tank, and I was wondering: how does one tell the difference between males and females? Is there a difference in color, or size? I noticed that one of them is a much brighter yellow than the other. I'm thinking that I have one male and one female, but that is just conjecture at this point.

[Fishyfanatic]

Labs are very difficult to sex until they reach maturity. And even then it can be very difficult. We have a female and I thought for the longest time that it was a male. She has the darker black coloration and distinct forehead. It wasn't until I saw her holding fry that we realized she is a female. Venting is the only way to 100% be sure of the sex.

[Thebluyak]

the females will generally have a white belly while the males will be solid yellow. The female will have a light dark ridge on her back fin while the males will be dark and distinct. The pec and anal fins will be very dark for the male while not at all for the female. Also the male will have a black line through his eye going vertically if I remember correctly. I could go look at mine now but the lights off.

[ManannanMacLir]

Thank you for the advice. I'll have to take a closer look at them tomorrow, with the information you gave me in mind. The reason I asked is that I'd like to add mostly females so as to reduce aggression.

[DeFeKt]

the females will generally have a white belly while the males will be solid yellow. The female will have a light dark ridge on her back fin while the males will be dark and distinct. The pec and anal fins will be very dark for the male while not at all for the female.

No offence intended here but basically you just described a poor quality yellow.
Fishy fanatic is right, the only sure fire way of telling is by venting...and waiting till the hold :P

The black line through the eye is also a 50/50 chance either way..

[FishAddict]

yes its hard to tell until the reach maturity the male will have a black ring around his mouth so thats an easy way to tell

[triazole]

reiterating what DeFeKt said, barring is a sign of questionable breeding, and not a way to sex yellow labs. and as fishy said earlier, venting or holding is the only surefire way to sex a lab.