The Department of Environment and Primary Industries and Victoria Police allege that abalone, rock lobster and shellfish were taken from the south-west Victorian coast to Melbourne, where they were sold on the black market over the past year.

They executed warrants in Melbourne's western suburbs earlier this month, arresting 14 people over offences against the Fisheries Act. Police also seized 12 vehicles and cash, and froze assets worth millions of dollars.

It is understood that people regularly drove overnight to raid reefs near Port Fairy, and returned to Melbourne in the mornings. The abalone was reportedly worth hundreds of thousands of dollars.

Seven of those arrested appeared at the Melbourne Magistrates Court on Monday.

Phuc Nguyen, Thanh Hai Nguyen, Thi Hung Van, Ca Nguyen, Ne Huynh, Han Dang and Van Nguyen were charged with trafficking commercial quantities of abalone, and selling and receiving abalone, rock lobster and other molluscs without authorisation. They were also charged with dealing with the seafood as proceeds of crime and agreeing with others to commit indictable offences.

All except Thi Hung Van were also charged with conspiring to traffick a commercial quantity of abalone, and taking seafood for sale without authorisation.

Magistrate Kay Robertson extended their bail until their next court appearance on March 3 on the same conditions.

They were all ordered not to associate with the other accused, except for those whose partners are also accused. They were not to possess any abalone or fishing equipment or engage in fishing activities. They were also ordered to surrender their passports and to stay away from any marine environment.

The other seven people arrested over the alleged syndicate are expected to appear in court on Tuesday.