Restoring Botany Bay’s historic reefs

The disappearance of shellfish reefs 

Since the arrival of European settlers, shellfish reefs have all but disappeared. Records show that oyster reefs were once plentiful in the Bay, with James Cook himself describing the “largest oyster shells” he ever saw. Interestingly, these oysters were likely to have been the Australian Flat Oyster (Ostrea angasi), which is now locally extinct in Botany Bay.

For European settlers, oyster reefs provided easily accessible food and building material. With a lack of limestone quarries, early colonial buildings such as the first Government House were built using shell mortar produced from shells and living oyster beds. The new colony was literally built and fed on a foundation of oysters.

The first sign of overfishing and over-dredging was seen in the rapid depletion of the Botany Bay oyster stocks. Unfortunately by 1896, the natural mud oysters of Botany Bay were declared extinct. 

With the exhaustion of natural oyster reefs, the local aquaculture oyster industry developed to meet demand. However, by 2001 disease killed up to 90% of the oyster population. This outbreak marked the fall of the local industry, with many farmers closing their business in the bay. 

A hopeful future

In recent decades, the river’s water quality has been recovering. With the introduction of eco-friendly practices, land re-development, and regulations on sewages. The natural populations of Sydney rock oysters in the estuary have shown an incredible resilience with signs of good health and growth. 

With cleaner water, less pollution and a healthy remnant oyster population, Botany Bay and Georges River is ready for the recovery of these lost ecosystems.

The Nature Conservancy, together with our partners Greater Sydney Local Land Services and NSW DPI Fisheries are working to restore these lost shellfish reefs.

With the support of the Australian Government, we’re committed to bringing these shellfish reef ecosystems back from the brink of extinction — for the benefit of both people and nature.

To kickstart this, the Botany Bay and Georges River Oyster Reef Restoration project was established in 2021. The goal of the project is to restore up to five hectares of the locally extinct Australian Flat Oyster (Ostrea angasi) and depleted Sydney Rock Oyster (Saccostrea glomerata) reefs, across three sites, one in Botany Bay and two in the upstream shores of the Georges River.

Benefits for people and nature

The return of the shellfish reefs to Botany Bay has multiple benefits, for the local community and nature. This includes:

• improved local fish populations, with beds and reefs acting as fish foraging, hiding, resting nursery grounds
• increase in local biodiversity, with reefs providing habitat for more than 200 species, including invertebrates, fish and birds, some of which are considered threatened and critically endangered
•  improved water clarity 
• protection of adjacent habitats from erosion 
• opportunities for people to enjoy recreational fishing, snorkelling and diving
• a boost for local, sustainable tourism and bird watching

Shellfish ecosystem restoration across Australia

With successful reef builds already in places like Victoria’s Port Phillip Bay and South Australia’s Adelaide, we’re excited to begin reef restoration in Botany Bay.

This project is a part of The Nature Conservancy’s national Reef Builder initiative to bring shellfish reef ecosystems back from the brink of extinction — for the benefit of both people and nature. The national Reef Builder project is currently restoring shellfish reefs in 13 sites across Australia.