Protestors against dredging to deepen Fremantle Ports Inner Harbour have promised to continue their fight despite work beginning on the project, the Freemantle Cockburn Gazette reported.

The dredging is part of a US$250 million expansion to ensure the port can cater for larger container ships.

Excavated sediments from the seabed will be suctioned into self-contained hoppers and transported to a pipeline offshore from Rous Head, before being pumped from the dredge into the enclosed Rous Head reclamation area.

Residents have expressed concern about the project, claiming plumes have already been detected in local waters, including the Swan River.