"Catfish" is slang for someone who creates a false identity online.
The prosecutor told Newry Magistrate's Court last month they expected to identify thousands of new victims across the world.
McCartney has remained in custody since his arrest in July and will reappear next month.
New Zealand Principals' Federation vice president and Hastings Intermediate School principal Perry Rush said it was time to talk about the effect of social media and the internet on young people.
"That conversation is long overdue and it is not taking place because we have this acquiescence to the power of social media giants within the context of not wanting to crimp and limit this competitive open-knowledge economy that exists.
"It's just simply not appropriate when we talk about children," he added.
Rush noted the minimum age requirement on most social media platforms and questioned why it was not currently enforceable.
"There is a reason why social media puts that age limit of 13 on.
"It is absolutely the case that thousands and thousands of children in NZ beneath the age of 13 are using social media.
"If social media companies themselves have an age limit, then I think it is a question for government to think about the reality of kids having access to these platforms as a consequence of the inability to enforce compliance."
NetSafe chief executive Martin Cocker said it was important for both parents and young people to be aware of the risk that exists worldwide, particularly on all communication platforms.
Cocker said once an offender had connected with a child, they tended to "convince that child to convince their other friends to connect with them".
"When kids go to school and they talk about what apps they're on, that encourages other young people to download those apps and if there is a particular service where risk is occurring, a lot then that can lead to a spike in a region or a localised spike."
He encouraged children to come forward "as soon as possible and for parents and school communities to be as supportive as possible to those that do".
Detective Sergeant Heath Jones said while no other children had come forward as of Tuesday there was still a lot of work being done by the Police Service of Northern Ireland.
"There may very well be more victims."
It was important that parents speak to their children about appropriate and inappropriate contact, and how to stay safe online, he said.
"To help your children stay safe you can also make sure you know who your children are making contact with online and which social networking sites they're using."
