Indigenous oyster fisheries persisted for millennia and should inform future management

The study addresses how Indigenous oyster fisheries functioned over millennia compared to the much more recent capitalist commercial fisheries that rapidly collapsed. It situates oysters as ecological keystones and culturally significant resources whose estuarine habitats expanded with post-glacial sea level stabilization. The research question centers on documenting the cultural significance, intensity, duration, and extent of Indigenous oyster harvest across eastern Australia and the Pacific, Atlantic, and Gulf coasts of North America and evaluating sustainability through time. The purpose is to integrate archaeological, paleoecological, sea level, and ethnohistoric datasets to show that Indigenous fisheries were extensive yet sustainable, contrasting with modern collapses, and to argue that contemporary management must incorporate Indigenous histories and participation. This is important for reframing baselines, recognizing managed pre-colonial ecosystems, and informing restoration and co-management.

The paper builds on historical ecology and conservation paleobiology, noting widespread 19th–20th century oyster reef declines and an estimated loss of up to 85% of 19th-century reef area by the early 21st century. Prior scholarship (e.g., Kirby 2004) emphasized capitalist commercial fisheries’ trajectories in North America and eastern Australia. Archaeological and paleoecological studies have highlighted long-term oyster use and resilience, but Indigenous fisheries are often underrepresented or mischaracterized as lightly fished. The authors synthesize these threads, emphasizing Indigenous knowledge systems, shell midden archaeology, sea-level histories, and historical catch records to contextualize Indigenous oyster harvests over thousands of years and to challenge narratives that ignore Indigenous management.

Study design combined regional syntheses across three focal areas: eastern Australia (southeast Queensland), Pacific Coast of North America (San Francisco Bay and Salish Sea/Pacific Northwest), and Atlantic and Gulf coasts of North America (New England to Florida). Data sources included: (1) secondary data from published and grey literature and authors’ datasets, and (2) primary data from recent excavations and museum collections.

• Site selection and variables: For each region, the team compiled oyster-bearing archaeological sites with robust chronologies and quantified oyster abundance, recording location, chronology, site type/use/size, excavation methods, and oyster abundance.
• Temporal analyses: They constructed regional time-series of the relative frequency of oyster-bearing sites per century of occupation (based on radiometric dates or diagnostic artifacts) and overlaid them with region-specific relative sea-level curves (from published sources or ICE_6G_C modeling) to relate oyster exploitation to estuary formation and stabilization.
• Abundance metrics: Relative oyster abundance within sites was assessed via two standard zooarchaeological measures: (a) minimum number of individuals (MNI), calculated by counting sided valves and using the higher of right/left counts; and (b) shell weight proportions. These metrics, while not directly comparable, each inform relative abundance trends and were plotted by site across time.
• Absolute abundance estimation: Where possible, the authors estimated total oysters represented per site by scaling MNI observed in excavated volumes to total site volumes. Site volumes were approximated from excavation data and mapped site extents; in some southern Atlantic and Florida cases, LiDAR and total station mapping provided higher-precision volumetrics.
• Ethnohistoric and ethnographic synthesis: The team systematically reviewed published and unpublished accounts documenting Indigenous oyster harvesting, processing, storage, trading, reef enhancement, and management practices, linking them to archaeological sites.
• Excavation and analysis protocols (primary data): Standardized unit excavations (0.25 × 0.25 m columns to 1 × 2 m units), screening over 3 mm or finer meshes, complete material retention, taxonomic sorting to least inclusive units, shell weighing, and MNI from non-repetitive elements (e.g., hinges). Museum bulk samples (e.g., CA-ALA-307) were processed via flotation; heavy fractions analyzed to >2 mm. Indigenous collaboration and consultation underpinned many recent studies, with acknowledgment of earlier studies lacking such engagement.

• Persistence and scale: Indigenous oyster fisheries were widespread and endured for 5,000–10,000+ years, tracking estuary development following Holocene sea-level stabilization. Despite intensive use, evidence of depletion or size decline is rare and localized.
• Regional abundance patterns:
  • Atlantic/Gulf coasts: Oysters are most abundant. In the southeastern U.S., oysters constitute over half of shellfish at most sites; at least 60% of studied sites have ≥90% oyster by weight. In Chesapeake Bay, 26 of 30 sites contain >90% oysters by weight. In New England, oysters are less dominant than hard and soft shell clams except at large Late Holocene Damariscotta River middens.
  • Pacific coast: Fewer large estuaries; oysters supplement diverse fisheries. San Francisco Bay shows strong temporal variability, with oyster contributions ranging from about 2% to 94% of shellfish weight. Northwest Coast high-oyster sites occur patchily in deltaic settings amid diverse harvested taxa.
  • Southeast Queensland (Australia): Sites show 20%–95% oyster by weight, with lower overall taxonomic diversity at some locations indicating targeted oyster harvest.
• Monumentality and cultural roles: Shell mounds and engineered deposits integrate subsistence with ritual, ceremonial, and political life. Examples include:
  • Crystal River (Florida): Mound A (~9 m high, ≥9,000 m² footprint) likely contained ~20–30 million oysters.
  • Whaleback (Maine): ≥6 m deep, ~105 × 37 m, composed almost entirely of oyster shell.
  • West Berkeley (San Francisco Bay): Massive oyster-rich mound with burials, indicating ceremonialism and feasting.
  • Booral Shell Mound (SE Queensland): ~1.4 m high, ~154 m²; ~5.9 million oysters harvested.
  • Smaller camps and ubiquitous pit features (eastern North America) cumulatively represent sustained intensive harvests; e.g., Chesapeake site 18D0439 (~1,400 m²) yielded an estimated ~2.3 million oysters.
  • Quantitative site-scale estimates (Table 1) demonstrate harvests reaching tens of millions to billions of oysters at some monumental complexes.
• Indigenous management and continuity: Ethnohistoric accounts document techniques such as seasonal harvests, roasting, storage (smoking/drying), reef enhancement with shell to attract spat, and possible oyster farming. Colonial records show early restrictions (e.g., 1622 Virginia oyster licenses limiting Indigenous access). Ethnographic mapping links historic oyster beds to archaeological sites (e.g., San Juan Archipelago).
• Contrast with capitalist commercial fisheries and collapse:
  • Chesapeake Bay: ~17,618,000 bushels (~1.7 billion oysters; ~1.1 billion pounds) in 1891/1892; post-1930 harvest <40 million pounds; 1980s <20 million; 1990s only a few million pounds.
  • Willapa Bay (WA): Native Ostrea lurida harvest peaked at ~150,000 bushels market-size plus ~350,000 bushels seed; fishery collapsed, replaced by non-native Crassostrea gigas; O. lurida now patchy and of concern.
  • Southern Queensland: Saccostrea glomerata peaked (~43.8 million oysters) c. 1891; rapid decline; today cultivated harvests in Moreton Bay are well under 2 million oysters annually.
• Interpretation: Indigenous fisheries were embedded in socio-ecological systems, supported by traditional ecological knowledge, social relationships, territorial governance, and watershed-scale stewardship, enabling long-term sustainability and setting the stage for later commercial exploitation.

Findings demonstrate that pre-colonial nearshore ecosystems were actively managed and closely intertwined with Indigenous cultural systems, contradicting notions of pristine or minimally used environments. Archaeological, ethnohistoric, and ecological records show Indigenous oyster fisheries were intensive yet sustainable over millennia, with monumental shellworks evidencing both scale and cultural significance. The displacement and exclusion of Indigenous peoples under colonial regimes disrupted these socio-ecological systems, contributing—alongside overharvest, pollution, habitat loss, invasive species, and disease—to modern fishery collapses. Incorporating archaeological deep-time records and centering Indigenous governance and knowledge are essential to effective restoration and management. Co-production of knowledge, co-management, and recognition of Indigenous stewardship are presented as pathways to rebuild resilient oyster reefs and associated ecosystems.

The study documents millennia-long, large-scale, and largely sustainable Indigenous oyster fisheries across North America and eastern Australia. By integrating archaeological abundance data, site-scale volumetric estimates, sea-level histories, and ethnohistoric accounts, it reframes baselines for oyster ecosystem health and management. The authors argue that effective restoration and fisheries governance must center Indigenous histories and include Indigenous communities as co-developers of strategies. Future work should: (1) expand standardized quantitative datasets across additional regions and sites; (2) further integrate Indigenous knowledge with archaeological and ecological data; (3) refine methods to detect past management practices (e.g., reef construction/farming) archaeologically; and (4) implement co-management frameworks and culturally grounded restoration initiatives.

• Data heterogeneity: Abundance metrics (MNI vs. weight) are not directly comparable; excavation and analytical methods vary across regions and studies.
• Sampling biases: Site visibility, preservation, discovery histories, and differential research intensity affect the archaeological record. Many sites remain uninvestigated or were destroyed by sea-level rise, development, mining, and other disturbances.
• Chronological resolution: Difficulties dating deposits immediately before European arrival in some regions can obscure late pre-contact trends.
• Environmental variability: Local isostatic and sea-level dynamics introduce regional complexity in correlating estuary development with harvest intensity.
• Management detection: Archaeological correlates of oyster management/farming are challenging to identify, potentially underrepresenting these practices.
• Data availability: Some datasets derive from unpublished reports or repositories requiring permissions; not all potentially relevant sites met inclusion criteria (e.g., lacking volume/MNI data for absolute abundance estimation).