The Maritime Union of Australia plans to hold protests until Friday.
About 100 waterside workers are protesting over pay and conditions outside the Kwinana Bulk Terminal in Naval Base.
The MUA and Fremantle Port held an emergency meeting a short time ago but failed to reach an agreement.
Earlier in the day the West Australian Transport Minister, Troy Buswell, accused the union of holding the port, and the state, to ransom with planned industrial action over roster changes.
Mr Buswell says its demands are fanciful, particularly in the current economic climate. He also took a swipe at the Federal Government’s Fair Work system saying it is failing the State’s economy which depends on the port.