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Indigenous people harvested oysters sustainably for thousands of years

Oyster fisheries around the world have suffered collapses over the past 200 years that have been attributed to overexploitation, climatic changes, disease and the introduction of alien species. This is particularly noticeable in countries where colonizers arrived and commercialized the harvest of this shellfish on a large scale. In the process, Indigenous peoples who had used the resource for hundreds, or even thousands of years previously, were displaced and marginalized. Today, as much as 85 percent of the 19th century oyster reefs have been lost and oyster fisheries have declined globally. 

Research into oyster fisheries has often focused on the years subsequent to the arrival of colonizers, and the data has been used to inform management practices, while the earlier use of the resource by Indigenous peoples has largely been overlooked or ignored. And yet these people depended upon oysters as part of their diet and economy, in addition to using them in social, ritual and cultural traditions. They were deeply connected to the coastal ecosystem and had indigenous knowledge derived from the historical use of the resource.

In a new, global study of Indigenous oyster fisheries, published today in the journal Nature Communications, scientists have excavated the remains of shell middens in areas of eastern Australia, the Pacific Coast of North America, and the Atlantic and Gulf of Mexico coast of North America, in order to expand on knowledge about oyster harvesting prior to the arrival of colonial populations. The study was co-led by anthropologist Torben Rick of the Smithsonian’s National Museum of Natural History, and Temple University anthropologist and former Smithsonian postdoctoral fellow Leslie Reeder-Myers.

“Oyster harvesting didn’t start 500 years ago with the arrival of Europeans,” said study co-author Bonnie Newsom, an anthropologist at the University of Maine and citizen of the Penobscot Indian Nation. “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.”

According to Rick, the new research expands on a seminal 2004 paper that documented the collapses of 28 oyster fisheries located along the east and west coasts of North America and Australia’s east coast. But the 2004 paper’s timeline in each location begins with European colonists’ creation of commercial oyster fisheries. In the current study, the aim was to deepen the historical background of those modern declines by documenting the Indigenous oyster fisheries at the same locations as considered in the 2004 paper. 

But the authors also aimed to highlight that Indigenous communities should be included in future management decisions pertaining to these resources since they have a valuable input to make. 

“Conservation today can’t just be seen as a biological question and can’t just be about undoing the environmental damage we’ve done in the modern era,” Rick said. “Instead, global conservation efforts should be coupled with undoing the legacies of colonialism which brought about the attempted erasure and displacement of Indigenous people all over the world.”

Rick, Reeder-Myers and 24 other researchers used information from shell middens at the sites studied in the 2004 paper. The team used data from previously published papers, unpublished records and their own research in order to quantify the numbers of oysters disposed of by indigenous peoples at these archeological sites. Some middens were small and perhaps only used seasonally, while others were massive and towered up to 30 feet in height.

The findings of the research show that oyster fisheries were hugely productive over a timescale of hundreds and even thousands of years, during which the shellfish were intensively harvested. Long before European colonizers arrived, the Indigenous groups in these locations harvested and ate immense quantities of oysters in a manner that appeared to be sustainable, as the availability of oysters did not appear to diminish over time. 

In North America, the highest midden came from an Island called Mound Key in Estero Bay on Florida’s Gulf Coast – it contained shells of an estimated 18.6 billion oysters harvested by the region’s Calusa tribe. About 200 miles north, in Cedar Key, Florida, a site known simply as Shell Mound features the remains of an estimated 2.1 billion oysters. On the Atlantic coast of the United States, the midden at South Carolina’s Fig Island boasts just under 75.6 million oysters, and a number of sites in Chesapeake Bay total around 84 million of these shellfish. In Australia, Saint Helena Island near Brisbane is estimated to contain roughly 50 million oyster shells harvested by Indigenous peoples over more than 1,000 years.

“We knew there were big sites in the southern U.S., but when we started to calculate just how many oysters were in these sites we were astonished,” Rick said.

Dating the shells at various middens revealed that the oldest oyster remains, found in California and Massachusetts, were harvested more than 6,000 years ago. The longest-utilized single sites (though not necessarily with perfect continuity) span some 5,000 years. 

In addition, the researchers measured the lengths of oyster shells dating back in history to find out whether smaller individuals became more common in younger deposits. According to Rick, if the oyster populations were harvested faster than they could recover, smaller individuals would have characterized more recent deposits. But the scientists found no evidence of decreasing shell size, suggesting that the populations were generally healthy and were not overexploited, despite the enormous numbers of individuals harvested.

The information from these ancient, sustainable fisheries offers insights to help restore and manage estuaries today, say the authors. They note that the findings show that Indigenous peoples in these locations had deep connections to oysters and that their living descendants are long overdue to be involved in decisions about how to manage what is left of this precious coastal resource

“The fact that there are so many oysters at archeological sites in so many different regions is an important lesson,” said Reeder-Myers. “These systems have a ton of potential and huge quantities of oysters can be sustainably harvested over long time periods if the ecosystem is healthy.”

Rick said he hopes that their findings are heeded by biologists and environmental managers and heighten public awareness about the deep connections of Indigenous peoples to coastal ecosystems around the world.

“What this study does is it says we need to start a broader dialogue when we look to restore an ecosystem or make conservation decisions,” Rick said. “In this case, that dialogue needs to include the Indigenous peoples whose ancestors stewarded these ecosystems for millennia. This broadening of perspectives can enhance biological conservation and help restore connections between Indigenous peoples and their ancestral homelands.”

Image Credit: Torben Rick

By Alison Bosman, Staff Writer

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