Reefs Return to Western Australia’s Swan River

The Nature Conservancy began restoring shellfish reefs in Western Australia’s Swan River around Attadale and Freshwater Bay five years ago. Before the 1920s, the river, known as Derbal-Yerrigan to the Noongar people, thrived with reefs built from millions of tonnes of shellfish. Roughly one million tonnes of limestone were removed from the riverbed from the 1920s to 1950s for building materials, degrading the habitat.

In 2023, the conservancy placed about six hectares of limestone on the riverbed and added 160 tonnes of mussels grown in Cockburn Sound to jumpstart growth. Though warm water caused initial mussel loss, shellfish populations—including oysters and scallops—have rebounded. The restored reefs now support fin fish and breeding stocks of recreational species like snapper.

The Department of Biodiversity, Conservation and Attractions will monitor the existing reefs. The Nature Conservancy now plans to install pilot reef structures near shorelines to combat erosion and protect habitats. Further study will determine the long-term success of these measures.