The Wellstead Estuary is a 13-kilometer-long tidal estuary fed by the Bremer River, which rises near Jerramungup and flows for 70 kilometers before meeting the Southern Ocean. This expansive aquatic habitat is globally significant, serving as a major feeding and recuperating ground for over 100 species of birds migrating along the East Asian-Australasian flyway. The estuary comprises a large lagoon and nine kilometers of narrow river channel, creating a dynamic environment where freshwater mixes with the ocean. When the estuary mouth is closed and the system is full, it becomes a highly productive fishery. The connection to the ocean, when the sand bar at the mouth breaches, can introduce marine species like blue swimmer crabs and prawns into the river system, further enriching the fishery.