The life and times of the local oyster

Mary Gardner

In some daring moment, you may have proclaimed ‘the world’s my oyster!’ But exactly what is an oyster’s world? Salty wet morsels on a half shell, what sort of life leaves them finally exposed on a plate at a fancy dinner?

Pearl oysters, a separate group from the edible oysters, live in the tropics of Australia. Here in the northern rivers, the rock oyster and flat oyster were foodstuffs of the Aboriginal people for thousands of years. Large middens hint at centuries of bygone meals.  Most of these are hard to find now because, from the mid 1800s, many were dug up and burned to create lime. This product was used partly in farming but more urgently for building. The British, wanting the type of housing they knew best, needed lime for mortar and cement. When the more obvious middens were used up, they pulled up live oyster reefs. This process was called ‘skinning’.

Another word that makes a person think. ‘Skinning’ meant peeling away from river banks and coastal areas kilometres of structures made over centuries by oysters. These reefs were like coral reefs: layers of dead shells glued together and topped with a living layer of animals.  (A variation of this communal living was the oyster bed.)

In either setting, these animals are filter feeders. They open their shells and circulate water across their gills for both oxygen and particles of food. In great numbers, they once cleared vast amounts of water. Individual oysters are clocked at clearing up to 190 litres of water a day.

Adult rock oysters change sex several times a year. Rock oysters simply shed eggs and sperm into the waters. Flat oysters are also sex changers but in a female mode the oyster collects sperm and broods the young inside the shell. About a week later, the youngsters are sent off. By either process, a new generation swims away, attaches somewhere and grows.

Either type of oyster reproduction en masse was also an opportunity for a feed by different schools of fish. Reefs were generally good for a meal of oysters or of other animals that made their homes there. The complexity is hard to picture. Different predators were a hazard for different sizes of shellfish. Certain sharks also ate oysters.

Still, many oysters survived. Oral histories suggest that Aboriginal people encouraged settlement of oysters by deliberately placing old shells or sticks in the water. Shellfishing was often considered women’s work. Is it possible that coastal regions were partly shaped by generations of women ‘gardening’ young oyster spat?

Back to ‘skinning’. Since shellfish doubled as everyday foodstuff for Aboriginal people and immigrants alike, laws tried to stop the destruction of live reefs and beds. ‘Skinning’, along with deforestation, literally muddied the waters. One place after another ‘lost’ their oyster reefs or beds. Marine food webs changed, as did water quality.

By the turn of the 20th century, legislation formalised oyster farming as a strictly commercial industry. Farmed shellfish were served in the oyster saloons of Lismore, Mullumbimby, Byron Bay and Brunswick Heads.  The best oysters in the country were said to come from ‘the Bruns’. They were sent to Sydney, Brisbane and overseas. The question today is which species of oysters were they? The ones now found at the markets are rock oysters. Old photos from before the cyclone of 1954 suggest that flat oysters were more abundant.

There isn’t an ending to this story. Exactly what happened in Brunswick Heads? How extensive were the oyster beds and reefs from Richmond River to the Tweed? An oyster on a plate may be two or three years old. Given the chance, they can live for decades, building reefs and beds, feeding fish and filtering water. Would we give these small animals such an opportunity?

Do you know about local oysters past? I would love to hear from you.

You can reply to Mary’s query about oysters by leaving your comment in the space below.