It is believed a man has been arrested over the discovery of a human head on Rottnest Island, off the Perth coast.

Stephen Ramon Cookson's head was found by an 11-year-old girl while beachcombing at Porpoise Bay earlier this month.

A team of forensic officers descended on a property at Golden Bay, south of Perth yesterday.

It is understood a man was arrested and taken in custody over the incident last night.

Cookson was a player in a major Western Australia crime syndicate and was due to stand trial later this year on serious allegations of drug trafficking.