Ancient Australians and Americans Ate Billions of Oysters Over Millennia

Precolonial indigenous communities in Australia and North America harvested and gorged on vast quantities of oysters. Yet, this copious consumption did not cause oyster populations to crash and become endangered, or even disappear as they have in many places today, new research published in the journal Nature Communications suggests. Precolonial oyster fisheries provided astonishing yields and were sustainably managed over thousands of years of intensive harvesting.  

The study, co-helmed by the Smithsonian Museum of Natural History’s anthropologist Torben Rick and Temple University anthropologist Leslie Reeder-Myers, investigated historical indigenous oyster fisheries in eastern Australia, and the North American Pacific, Atlantic and Gulf of Mexico coastal regions. To arrive at its findings, the study combined historical catch records with archaeological data on oyster abundance and geographical distributions, as well as ethno-historical accounts from indigenous communities.

Oysters played a central cultural and dietary role in these communities, and they were actively managed and sometimes “farmed” by the communities, the study claims. The authors also urged that modern oyster harvests and degraded reefs could be revived by using their study insights and “relearning” how ancient indigenous communities managed this resource. According to The Guardian, almost 85 per cent of the world’s 19th-century oyster reef areas have been lost in the past 200 years.

This is a giant shell mound of mainly oyster shells at the Crystal River site in Florida. This image shows an archaeological mapping project at the site, where a modern staircase and platform have been built on top of one of the huge prehistoric shell mounds. (Victor Thompson / Smithsonian)

Indigenous Oyster Farming Wisdom Offers Modern Insights

The authors documented shell middens or mounds in both the US and Australia that contained literally billions of oyster shells. Mound Key on Florida's Gulf Coast contained the largest amount, with some 18.6 billion oyster shells consumed by the region's Calusa tribe, reports CNN. The biggest shell middens were up to 30 feet (9 meters) high and served as important sacred ceremonial structures. Smaller middens were likely only in use seasonally. The oldest shell middens in California and Massachusetts date back nearly 6,000 years and some sites remained in continual use for over 5,000 years.

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Along Australia’s Great Sandy Strait in Queensland these middens were “deliberately made mounded structures as monuments on the landscape,” said Professor Ian McNiven, a study collaborator, reports the Guardian. The Booral shell mound, containing some 5.9m oyster shells, on the mainland opposite K’gari (Fraser Island), is 1.4 meters (4.5 feet) high, and covers an area of 154 square meters (1,657 square feet). “It [Booral] goes back 3,000 years – it is just jam packed with millions of oyster shells, showing that there was very intense harvesting of oysters in the past,” McNiven added.

This giant Crystal River shell mound in Florida, primarily made of shells from oysters, shows just how rich these oyster beds were thousands of years ago when the indigenous ensured they remained a sustainable resource with their management wisdom. (Victor Thompson / Smithsonian)

Stupid, Disastrous Modern Oyster Farming “Management”

Oyster populations in these regions, both in Australia and North America, began to dwindle soon after European colonizers arrived and began to practice commercial oyster fishing. The annual harvest in southeast Queensland of the native Saccostrea glomerata, commonly known as Sydney rock oysters, peaked in 1891 with about 43.8 million oysters, reports CNN.

This rapid drop in modern oyster harvests, on beds that the indigenous managed sustainably for millennia, caused a rapid population declines from places like Chesapeake Bay on the US east coast, San Francisco Bay on the west coast, and Botany Bay near Sydney. “Whatever the oyster fishing technique was, it was clearly unsustainable and it literally collapsed,” McNiven said to the Guardian. 

A dense shell midden deposit, spanning the past 1,000 years, during excavations at a Tseshaht First Nation village in the Pacific Northwest. (Iain McKechnie / Smithsonian)

Indigenous Knowledge Indispensable for Oyster Reef Survival

McNiven explained that the indigenous people sprinkled empty oyster shells back on the sand flats to create a base for the next generation of oyster larvae to attach to. Oysters weren’t collected year round but only in the “right” seasons.

Licensing of oyster banks and greedy commercial harvesting, without any effort to replenish stocks, resulted in the massive drop in oyster populations across the modern world. A combination of overfishing, runoff from agriculture, and clear-cutting of forests, basically “killed” the huge oyster beds that the indigenous managed so well for so long.

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Any serious solution to revitalize existing oyster populations must make use of this reservoir of indigenous knowledge. “Oyster harvesting didn't start 500 years ago with the arrival of Europeans. Indigenous peoples had a relationship with and understood this species well enough to use it as part of their subsistence and cultural practices. Indigenous peoples have a lot to offer in terms of how to engage with this natural resource in ways that are sustainable,” said study co-author Bonnie Newsom to CNN.

Top image: Thousands of years of oysters and oyster farming by the indigenous peoples of Chesapeake Bay lay hidden in this coastal oyster shell layer. A recent study on oyster farming by indigenous peoples in Australia and North America is supplying new insights for managing highly degraded modern oyster beds.   Source: Torben Rick / Smithsonian

By Sahir Pandey