oh good link there Chi
It can help to swipe a bit of gentian violet over the region and wipe it off to help show the parts a little easier.
It is also possible they are still too young to make identification difficult.
You can post the pictures right in the post using the image button to the right of the link button at the top of the post box like this.
Right. I've seen that picture, it doesn't help with these do they? If you base it on those pictures all my fish look like males, and I know that's not true because they bred. The second picture has me putting red coloring on it, that doesn't help either... These are 7-9 inches fish, they can't possibly be too young. I guess no one want to give it a guess?
one on the bottom looks male.
angle is kinda poor for me to tell the one on top.
One in the middle might be a cross dresser I don't know.
The last tilapia and the bottom one in the 2nd to the last picture are females. (they have slits that they use to release the eggs).
Cant tell about the others. (this is common, even the scientist types make a lot of mistakes when using visual identification.).
The best technique we've had (so far) is to let the alpha male chase off the smaller males and court the females.
Challenging, is why so many grow out operations use the hormone treated fish.
I've asked the same question and the experienced folks (professional breeders) recommend sexing by observed behavior over genetalia (sp?). Anyway, they recommend putting 4-6 breeding aged Tilapia together, preferably in a 55gal + size tank and observing behavior. The dominant male/males with show themselves quickly and can be separated as required. Females will avoid conflict and stay back until they've produced eggs, then at that point will come to the nest area to deposit eggs. The goal being to pair a female with a large, dominant male to insure a good line.
I know my nutshell explanation is not the best, but dig a little on the subject - it works. A while back I lost my breeding pair and recently used the "behavior method" to find my new pair. It was a bit confusing at first because I believe I confused lower ranking males with females. It just took some time and observation and they pretty much work it out before your eyes.
Like Joel, I was not successful sexing by comparing pictures online with my fish...even large fish. The behavior method did eventually get me a breeding pair.
I found when we had tilapia, some you could definitely see the gender by looking at the parts while others were so ambiguous that is was impossible to tell. I don't know if this was due to age, or "time of the month so to speak."
To manage the more controlled breeding you will definitely want a large aquarium where you can see them well and learn to distinguish behavior as well as the variations in coloration between male/female.
If you are just trying to get lots of fingerlings and not really worried about breeding quality, I had my best luck throwing a dozen tilapia into a duckweed pool of over 300 gallons and ignoring them other than to toss some feed in once a day. I got lots of small fingerlings that were great chicken treats. (my chickens love the pumpkin seed size fingerlings, easy to see and bite size yummies to them.)
There is simply no substitute for spending lots of time observing your fish.
I used to breed angelfish commercially,
and they are notoriously difficult to sex.
When I began, I almost never could sex them better than flipping a coin.
After raising twenty thousand or so
I could sex them with about 85% reliability
from across the room!
Just watch them.
It's more fun than television anyway.
There was some confusion when my breeding tanks got move and I was sick with chicken gunya, so all the fish got mixed up.
I went through all my tanks to today and found a number of the above, as i was a little unsure I put then into a open top IBC and will have to wait to see who nest and who hides?