Quirks & Quarks

Indigenous people harvested huge amounts of oysters sustainably through history, study finds

A recent study shows that for thousands of years, Indigenous peoples were harvesting tonnes of oysters sustainably. Researchers say this shows that it’s possible to do large-scale harvesting without harming ecosystems.

Researchers studied huge shell piles dating back thousands of years to understand ancient harvests.

In a new study, archaeologists analyzing ancient shell piles found that they reveal a history of a very active yet sustainable oyster fishery. (CRISTINA QUICLER/AFP via Getty Images)

A recent study has shown that for thousands of years, in sites around the world, Indigenous peoples were sustainably harvesting large quantities of oysters.

Researchers believe this could inform modern-day fisheries about how to harvest large amounts of food without harming ecosystems.

"People were harvesting just a massive amount of oysters. Some of these sites have over a billion oysters, and many have over tens of millions of oysters in them," said Torben Rick, a curator of North American archeology with Smithsonian's National Museum of Natural History.

The research built upon a landmark 2004 study, which looked at the collapse of 28 oyster fisheries along the coast of North America and Australia since the 1700s. Rick and his colleagues wanted to extend the history of those fisheries back several thousand years to get a broader understanding of oyster populations over time, and found that prior to colonization, the fisheries were thriving.

"That abundance doesn't really drop out. It's continuous all the way up through early contact and with Europeans and the onset of colonialism," he said.

The study was published this month in the journal Nature.

Billions of shells, dating back thousands of years

Rick and lead co-author Leslie Reeder-Myers assembled an international team of 24 researchers, including several Indigenous scientists, specializing in the areas that were analyzed in the 2004 report.

To get a clear picture of the history of the fisheries, they looked at mountains of discarded oyster shells, called middens, which date back thousands of years. The largest sites studied were in Florida, where one midden contained the remains of an estimated 18.6 billion oyster shells.

"They're really just a treasure trove for telling us all about the things that people were doing in the past," Rick told Quirks & Quarks host Bob McDonald. "There's literally a story written in the landscape."

A mountain of discarded oyster shells dating back thousands of years as seen in Florida. Florida's Gulf coast contains some massive shell piles that are estimated to contain billions of oyster shells. (Victor Thompson)

Another such site was along the Damariscotta River in Maine, where towers of white oyster shells are still visible today.

"You would have been able to travel up and see these massive white mounds over six meters deep. They're like mini mountains, actually," said Bonnie Newsom, an assistant professor of anthropology at the University of Maine and citizen of the Penobscot Indian Nation. Newsom was also a co-author of the study.

It shows us the strategies that work... It is a different type of harvest. It is a different approach on a different scale.- Torben Rick

The shell heaps were far more than just a place to dump kitchen waste — archaeologists have found numerous structures within the middens to suggest that people would often live on top of the shells, or use them as important sacred ceremonial spaces.

"The shell mounds or shell heaps were used in a variety of ways," said Newsom. "We often find house floors within them. We often find other kinds of hearth features. People were living their day-to-day lives at these locations on occasion. We also know that people bury their dead at these locations."

Close-up of a deposit of oysters on the Damariscotta River in Maine. Sites like this contain massive quantities of oysters harvested some 2,200 to 1,300 years ago. (Bonnie Newsom)

The layers of shells in the middens showed a consistent pattern at the many sites they studied. The oyster harvest was intensive but reliable throughout the centuries. They also found that the oysters themselves remained a similar size over time, which also suggested a sustainable harvest. The animals would have gotten smaller over time if they'd been stressed by over-fishing, Rick explained.

"When you think about that kind of harvest, it's pretty amazing," he said. 

Informing modern fisheries

As for how the fisheries were able to be so consistent despite the intensity of the harvest, Newsom suggests that the Indigenous worldview of seeing animals as equals alongside humans played a large part.

"To harvest things sustainably, it requires a respect for the species that you are engaging with. But it also requires an acknowledgement that this quote-unquote 'resource' is not exclusively yours. It belongs to everybody living today and as well as those that are coming behind us."

Rick believes that this could help guide modern fisheries, which are not only important for human sustenance, but also for the health of the watershed.

"Oysters are amazing engineers. They provide habitat for other organisms. They're great for seagrass. They filter out excess nutrients out of the water. So they're really keystone, important ecological organisms."

A dense shell midden deposit spanning the past 1,000 years is exposed during excavation at a Tseshaht First Nation village on Vancouver Island. (Iain McKechnie)

The results suggest, he added, that people can keep fisheries healthy as long as they take care of the ecosystem first, before worrying about extracting as much food as possible.

"It shows us the strategies that work," he said. "It is a different type of harvest. It is a different approach on a different scale."

Rick added that Indigenous people "were seeing [oysters] as something integrally linked to the entire watershed, to the entire land and seascape in which they're living, which all of those things are interrelated and which they're a fundamental component of, not something they're separate from.

"And I think that part of it is a very important part of why it worked."

Produced and written by Amanda Buckiewicz.