Oyster farming on Georges River, commercial aquaculture of Sydney Rock Oysters, in the Georges River estuary of New South Wales, Australia, occurred between around 1870 and 2023. Production peaked in the 1970s. In the financial year 1976–1977, the river produced 2,563 tonnes of oysters, over a quarter of the record statewide production total of 9,375 tonnes (the state total being equivalent to 204 million individual oysters). Following a series of setbacks after that year, an outbreak of QX disease in 1994, all but totally destroyed the industry on the Georges River; the development of QX-resistant strains came too late to save much of it. In 2023, the last oyster farm in the estuary was forced to close, and its future as an oyster growing area is now uncertain.
Before commercial exploitation
Before the arrival of the first European colonists, Georges River was different in several ways to now. The land adjacent to its shores was not urbanised, nor had there been extensive land clearing within the river catchment. The river itself was less silted. Mangrove forests were not as extensive, and much of their ultimate area was salt marsh habitat, now vestigial and endangered in the estuary. There were also large, naturally occurring oyster reefs in the estuary and Botany Bay.
The extent of the natural oyster beds in New South Wales was mapped, as part of the work of a Royal Commission into the oyster industry in 1876, but these records were lost in the Garden Palace fire in 1882. It is known, however, that the natural beds in the Georges River estuary were once extensive; one natural bed, off Connells Point, was recorded as being a long by wide. The Royal Commission's report described the natural beds as, "close set clumps of five or six oysters and two or four clumps thick all over the bed, averaging about eighteen mature oysters beside spat on every 5 square inches over an unbroken bed of shell on a tolerably hard bottom".
The river was used as a food source by the Aboriginal people who lived along its shorelines. The harvesting of seafood from the estuary by the traditional owners had little if any impact on the otherwise pristine state of the estuary environment.
Oysters thrive in the waters downstream of Salt Pan Creek. In this part of the river, the right bank of the river (southern side) is a part of the traditional land of the Gweagal clan of Dharawal people. Opposite, on the left bank (northern side), are traditional lands belonging to either Dharug people or coastal Eora people, both of whom spoke a common language. Georges River Council acknowledges that the Biddegal/Bidjigal/Bedegal clan of the Eora are the original inhabitants and custodians of land and water in the Georges River LGA.
For people living by the estuary, oysters were an important food. Over thousands of years, large middens consisting largely of oyster shells accumulated near the river. The contents of the Aboriginal middens reveal the species of oysters that were present before colonisation. The middens contain a mixture of the Native oyster (Ostrea angasi), also known as the flat or mud oyster, and the Sydney Rock Oyster (Saccostrea glomerata). The Native oyster became locally extinct in the Georges River, in 1896.
The Aboriginal presence continued for many years after colonisation. An early oyster farmer recalled that there was a lone Aboriginal man living traditionally, in a rock shelter at Audrey Bay, Illawong, as late as the 1880s. There was also an unofficial Aboriginal settlement at Salt Pan Creek, until the early 1940s.
Early commercial activities
Lime burning The predominant bedrock of the Sydney region is Hawkesbury Sandstone and, in some areas, Wianamatta shale. The sandstone was useful as a source of stone blocks for building and the shale for making bricks. However, there was no limestone, conveniently near to Sydney, which could be burnt to create lime, used to make lime mortar for masonry building work. Lime was also needed to treat acid soils for agriculture.
In the early decades of the colony of New South Wales, oyster shells were burnt to create lime. Because the Georges River was naturally endowed with oysters, some early colonists in the area were lime burners. One was John Alford, after whom Alfords Point is named, who supplied lime from the Georges River for the construction of the Landsdowne Bridge. The practice of lime burning gave rise to the name of Lime Kiln Bay, where there were lime kilns near the shore, in what is now Oatley Park. There were also lime kilns, on Cooks River, which used shells from Botany Bay and Georges River.
Because of its large and heavy shell the Native, flat, or mud oyster was preferred for lime production. Colonists had a preference for the taste of the 'cluster' or rock oyster, which also had better keeping characteristics. The sub-tidal oyster beds in the river contained mature oysters of both species.
Demand for lime outstripped what could be obtained from dead shells, and live oysters were dredged from the estuary, and burnt to make lime. In 1868, after sources of limestone had been found outside Sydney, and the oyster beds were becoming depleted, the colonial government banned the practice of dredging live oysters for lime. Lime burning continued, resulting in the destruction of some Aboriginal middens.
An early attempt at oyster farming A colonial politician and landholder, Thomas Holt, had made a tour of the French oyster farming industry around 1863. After returning to Australia, he bought land on the estuary foreshore, in 1864. On that land, he attempted to emulate the French technique of oyster farming using claires, which are long rectangular ponds excavated into former salt marshes. The water in the claires was refreshed using tidal flows, but is also augmented by rain, keeping it slightly less saline than seawater and so more suitable for fattening oysters. Holt was intending to farm the Sydney Rock Oyster, but the method he used was possibly more appropriate to a sub-tidal species such as the Native flat or mud oyster (Ostrea angasi); although a different species, Ostrea angasi has a superficial resemblance to the European flat oyster (Ostrea edulis), which when finished in claires becomes the renowned Belon oyster.
Around 1870, Gwawley Bay, since redeveloped as the canal estate, Sylvania Waters, was the site of Holt's oyster farming project. Its shore was also the site of Holt's house, Sutherland House. He had a bridge built across the opening of the bay, into which were incorporated flood gates to control the tidal flow, and had claires dug into low-lying land bordering the eastern side of the bay. The land alongside the claires, which had been raised using spoil dug from the claires, was used for grazing cattle and alpacas. Holt's claires were 22 feet wide (another report stated from 14 to 33 feet wide) and totalled 30 miles in length, with water depth at low tide varying between four inches and two feet. Holt had earlier enclosed nearby Weeney Bay, using piles, and oyster spat was gathered there. Oysters were lost due to the climatic temperature and turbidity of the water in the claires. With hindsight, it was also much more labour-intensive than necessary, under the conditions prevailing on the Georges River. Production actually increased once the flood gates at Gwawley Bay were removed, and some large and good quality oysters were grown. However, the venture was uneconomic, and it ended after a few years. Holt was reported to have spent £10,000 on the venture, a large sum for the time.
Holt's venture was an early attempt at sustainable oyster aquaculture in the estuary, and his oyster beds in the bay were still producing oysters as late as 1888. However, the French technique of oyster growing would never be reattempted in Australia. The claires, locally called 'channels', were still there in the early 1920s, and still discernible in a 1953 aerial photograph of the area. Both Gwawley Bay and Weeney Bay would later be and long remain the sites of commercial oyster farms, using other methods.
A lasting legacy of Holt's time was that Gwawley and Weeney Bays were, uniquely in New South Wales, privately owned waterways. Much later, in 1963, that privately owned status would lead to the end of oyster farming at Gwawley Bay.
Dredge harvesting and diving The focus shifted, from lime production, to dredge harvesting of oysters as a food, taken from the remaining naturally occurring oyster beds. In the 1870s, the natural oyster beds in the estuary were leased to two brothers named Emerson, one of whom, Alfred Emerson, was the proprietor of the Sea Breeze Hotel, at Tom Uglys Point, now the most southerly part of Blakehurst. He established his depot on O'Connells Bay, now known as Connells Bay.The Book of Sydney Suburbs, Compiled by Frances Pollon, Angus & Robertson Publishers, 1990, Published in Australia , page 70
Each oyster dredger typically had their own boat, equipped with an oyster dredge and a windlass. The oyster dredger would row to the dredging location. He would then either anchor his boat or attach it to a stake driven into the bottom. He would then let out a warp line to allow the boat to drift with the tide, out to the length to be dredged. The dredge would then be thrown over the stern, and the windlass first used to haul in the warp line, both pulling the boat back to its starting position and dragging the dredge along the bottom. The windlass was then used to raise the dredge, containing oysters, and empty its contents into the boat. The dredge itself consisted of an iron frame with a rectangular opening that led into a net, made of interlocking iron rings, closed at the far end. The dredges used on Georges River were around 4 foot six inches wide (1.372 m), but would be substituted with a narrower one, 2 foot six inches (0.762 m) wide, if there were likely to be rocks or other obstructions on the bottom. The water in which dredging operations took place in the Georges River estuary varied between 14 feet (4.3 m) and 50 feet (15.2 m) in depth. In shallower water, tongs were used.
For a time, large harvests were taken, depleting the natural sub-tidal beds. Criticisms of dredging were that it damaged many of the oysters, so that a portion were unsalable, and it was indiscriminate, resulting in many immature oysters being lost. It was also ultimately unsustainable and damaged the natural oyster beds and disturbed the bottom of the estuary.
As oysters became scarcer, divers were employed by Emerson to harvest the remaining oysters growing in parts of the estuary that were unsuitable for dredging. Diving was used as early as 1876. Divers worked from punts, and up to around forty-five feet of water. An implication of divers working to those depths is that the turbidity of the river water, in those times, was lower than it is now.
The river has sharks, but divers believed that they were able to deter these sharks by opening the wristband of their diving suit and releasing large air bubbles into water; divers were more concerned about annoying bream attracted by broken oysters. A criticism of the divers was that, being paid by the bag, they indiscriminately took both large and small (immature) oysters, inhibiting the breeding of oysters in the natural oyster beds.
Oyster beds were replenished using small oysters that had settled on rocks and mangroves elsewhere in the estuary, from around 1873. Smaller oysters from Port Hacking were relocated to the Georges River, to replenish the natural oyster beds. Even with some replenishment, by the beginning of the 1890s, New South Wales oyster production became unable to fully satisfy domestic demand for oysters, and large numbers of oysters were imported from New Zealand and Queensland.
Oyster farming
Suitable conditions