The 47-year-old man has been charged with 46 offences after police launched an investigation in far north Queensland’s Gulf of Carpentaria.
Police said the probe began last year after reports a man allegedly threatened numerous deckhands on board his fishing vessels.
The man is also accused of assaulting crew members and withholding food and water.
Police said an illegal firearm was located after detectives searched a Karumba address and four fishing boats last week.
The Karumba man was on Wednesday charged with a string of offences including 18 counts of common assault and five counts each of torture and slavery.
He has been remanded in custody and is set to appear in Cairns Magistrates Court on February 9.
Police said they were appealing for “witnesses and victims” to come forward.
“If you have information that could assist this investigation, we want to hear from you,” Detective Sergeant Bradley McLeish said.
“Victims who may be subject to harassment or intimidation in relation to speaking to police are assured that all offenders will be held accountable for their actions.
“Anyone making threats to potential witnesses or victims can expect a visit from detectives very soon.”