He allegedly learned of her age in early March and in an online conversation told the girl she was "beautiful for only 9 years old".
A 14-year-old Wellington girl who has used the site said it contained "lots of nudity".
Florida newspaper the Ledger reported that the investigation into Fenstermaker began in June when New Zealand police contacted the FBI's violent crimes against children task force.
They told the FBI a man who called himself Mac and lived in Florida had been inappropriately chatting with a young girl for three months before her father became aware of it.
"You usually come across people who are a bit weird so you exit out of them until you find someone that you want to talk to.It's mainly just old men who probably just go on there for a bit of a sexual good time."Cocker's advice to parents was to teach their children to use the internet ethically and safely."There are basic conversations that adults should have with their children about people misrepresenting themselves, and that some people would want to do you harm, and you and the child should work together to make sure this doesn't happen."Omegle does not pretend to be suitable for children.