An oyster bed in the Pacific Northwest. Toan Chu, Unsplash

Oysters were harvested sustainably for thousands of years by Indigenous peoples, study finds

Could traditional knowledge hold the answers for future oyster fishery management?

Indigenous communities had harvested oysters for thousands of years before they were colonized by Europeans, who then oversaw the rapid collapse of these sustainable fisheries, according to research published this May in Nature Communications.

The study authors looked at ancient oyster fisheries across the Atlantic and Pacific coasts of North America and eastern Australia and found evidence of intensive oyster harvesting dating back more than six thousand years in some areas. These oyster fisheries appeared after sea levels stabilized following the end of the last ice age, when the estuaries that many oyster species depend on became established.

“An interesting finding from this study is that many locations on the coast have had stable oyster populations for thousands of years. As we work toward restoring this species, these data can help guide where restoration should occur,” says Marco Hatch, an associate professor of environmental science at Western Washington University and an author of the study.

“Rather than relying on models and assumptions of where oysters might thrive, we can use thousands of years of data to direct restoration efforts,” adds Hatch, who is also a member of the Samish Indian Nation, the territory of which covers the central and southern San Juan Islands in Washington State.

That such a finding has only now appeared in a scientific journal is no accident. Indigenous traditional knowledge, developed through observation by communities over thousands of years, has long been viewed as less reliable than modern science because it is perceived as “anecdotal” or “imprecise” when it appears to challenge scientific “truths,” Biodiverse lands have also at times been regarded by non-Indigenous researchers as “wildernesses” that, ironically, must be protected from the Indigenous peoples who have shaped and managed such landscapes for millennia.

“Until recently, many scientists perceived Indigenous people as having a very ‘light’ footprint on their landscape and, living in such small communities, that they had minimal impact on their environment,” says Leslie Reeder-Myers, an assistant professor of anthropology at Temple University and an author of the study. “This paper shows that this is a false impression – Indigenous peoples in some areas harvested billions of oysters at just a single location.

“Their light footprint, even if it existed, wasn’t due to population numbers but to landscape management practices. This is of increasing interest to many ecologists, and the study of traditional knowledge or local knowledge has recently become much more widespread.”

Researchers at a dense shell midden deposit spanning the past 1,000 years that was exposed during excavation at a Tseshaht First Nation village in the Pacific Northwest. Photo by Iain McKechnie
Researchers at a dense shell midden deposit spanning the past 1,000 years that was exposed during excavation at a Tseshaht First Nation village in the Pacific Northwest. Photo by Iain McKechnie

Aside from being a delicacy, oysters, when clustered naturally in reefs, also clean the local water and prevent coastal erosion. Yet an estimated 85 percent of oyster reefs have disappeared globally due to overharvesting, land development, pollution, disease and other factors. “Even a good harvest today is just a fraction of what it was a few hundreds of years ago,” says Reeder-Myers.

The Nature Communications study found that rather than the coastlines being “pristine” or untouched by people, that they were in fact sustainably managed landscapes. As an example, the research cited a technique still used by the Quandamooka Aboriginal people living today in Australia’s Moreton Bay, who use old oyster shells to construct artificial reefs for raising young oysters that are used to restock depleted reefs and thereby extend the seasonal availability of the shellfish.

Besides looking at sea level data and historic accounts of oyster harvests, the researchers also studied shell middens – archaeological sites where shells were dumped after shellfish were consumed – to gauge the intensity of oyster consumption in an area, as well as oysters’ relationships with Indigenous peoples’ culture and society. 

Some shell middens were found to have a ritual or ceremonial significance: a massive shell mound in San Francisco Bay dating back 6,000 years contains burials, and a mound on Florida’s Gulf Coast that once contained possibly 30 million oyster shells was flattened at the top to form a platform for ritual activities.

But these sustainable fisheries collapsed soon after Indigenous peoples were colonized by European settlers due to overharvesting, pollution and other developments. In one example cited by the study, 1.1 billion pounds of oysters (or 1.7 billion individual oysters) from Chesapeake Bay were harvested within one year in the 1890s alone. But such unsustainable harvests led to a decline in output over time, down to only a few million pounds in the 1990s. 

“It is important to recognize the connections between environmental justice and conservation biology,” says Torben Rick, the curator of North American archaeology at the Smithsonian Institution’s National Museum of Natural History and an author of the study. “There are direct links between colonial atrocities waged on Indigenous peoples and the subsequent degradation of marine and terrestrial ecosystems.”

The Crystal River site in Florida is a massive shell mound, mainly oysters, that shows the dense accumulation of shell and other material. Photo by Victor Thompson
The Crystal River site in Florida is a massive shell mound, mainly oysters, that shows the dense accumulation of shell and other material. Photo by Victor Thompson

Although much damage has already been done, efforts are now underway in some places to restore ancient fisheries. Around Chesapeake Bay, restoration initiatives have been introduced in several rivers, with some water-filtering benefits already visible.

“There are signs that some of the fisheries are recovering – although not to historical abundance – but climate change and other processes pose significant challenges, and we need concerted effort to ensure oyster sustainability in the future,” says Rick.

The study authors recommended that oyster fisheries management involve Indigenous communities, such as by applying more traditional knowledge in research and involving Indigenous peoples in management processes, all the way up to setting aside oyster fishery areas for their direct management. Aside from boosting oyster harvests, such efforts could be a step in returning stewardship of the land back to the groups who had lived there for millennia.

“Archaeology can show the depth of Indigenous connections to ecosystems and the breadth and intensity of ancient fisheries,” says Reeder-Myers, “but there is no need to extract Indigenous knowledge from the past when we can simply include Indigenous people and their knowledge in the present.

“There are descendants of these people alive today – some of them helped write this paper. However damaged these fisheries might be, they still represent the ecological heritage of people who were forcibly removed from these areas in the past. If we continue to make the decision to exclude them, we are continuing to practice colonialism.”

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