Estimating the Seasonality of Bent-Nose Clam (Macoma nasuta) Harvesting at a 3,000-Year-Old Ancestral Ohlone Site (CA-ALA-11) on the San Francisco Bay

ABSTRACT

This article investigates the harvest month for bent-nose clams (Macoma nasuta) at CA-ALA-11, an estuarine site in the modern-day city of Alameda along the San Francisco Bay. The archaeological deposit in which the clam shells were recovered dates primarily to the Early Period (3,350–2,550 cal BP) and Early-Middle Transition (2,550–2,150 cal BP), although some activity continues through 2,650 BP. Season of harvest estimates for clams offers insight into Indigenous use of estuarine resources and the degree of sedentism or length of habitation at this locality. Water salinity varies predictably in San Francisco Bay, from annual lows in winter to highs in summer. We used oxygen isotopes (δ¹⁸O) to estimate season of harvest by sampling at the intact terminal growth edge of the shell, which records salinity at the time of harvest. Three additional samples represent earlier periods of shell growth. Results show that while clams comprise a minority of the shellfish harvested, clamming took place between January and August, with a marked peak in mid-winter (February). There is no evidence for fall harvesting, which suggests that people were either not living at CA-ALA-11 during this time or focused on acquiring other seasonally available foods. We compare these results to previously published data on seasonality of clam harvesting from five other San Francisco Bay area sites.

RESUMEN

Investigamos el mes de cosecha de almejas de nariz torcida (Macoma nasuta) en CA-ALA-11, un sitio estuarino en la actual ciudad de Alameda en la Bahía de San Francisco. El depósito arqueológico en el que se recuperaron las conchas de almeja data principalmente del Período Temprano (3,350–2,550 cal BP) y Transición Temprano-Medio (2,550–2,150 cal BP), aunque alguna actividad continúa hasta el 2,650 BP. Las estimaciones de la temporada de cosecha de almejas ofrecen información sobre el uso indígena de los recursos estuarinos y el grado de sedentarismo o la duración de la habitación en esta localidad. La salinidad del agua varía de manera predecible en la Bahía de San Francisco, desde mínimos anuales en invierno hasta máximos en verano. Usamos isótopos de oxígeno (δ18O) para estimar la temporada de cosecha tomando muestras en el borde de crecimiento terminal intacto de la concha, que registra la salinidad en el momento de la cosecha. Los resultados muestran que, si bien las almejas constituyen una minoría de los mariscos recolectados, la recolección de almejas se llevó a cabo entre enero y agosto, con un marcado pico a mediados de invierno (febrero). No hay evidencia de cosecha de otoño, lo que sugiere que las personas no vivían en CA-ALA-11 durante este tiempo o se concentraron en adquirir otros alimentos disponibles estacionalmente. Comparamos estos resultados con los datos publicados anteriormente sobre la estacionalidad de la recolección de almejas en otros cinco sitios del área de la Bahía de San Francisco.

KEYWORDS:

• San Francisco Bay Area
• ancestral Ohlone
• clam harvesting
• oxygen isotopes
• seasonality
• Early Period
• Macoma nasuta
• estuarine resources

Acknowledgements

Thank you to graduate students Roshanne Bakhtiary, Diana Malarchik, and Jessica Morales for providing feedback and support through early drafts of this research. Special thanks also go to Corrina Gould, who is a representative of the Ohlone and supported us through this project. Lastly, we thank Mark Grote for his help with the quantitative analysis included in this article. Funding for this research was provided to the senior author from the Sacramento Archaeological Society and the Pacific Coast Archaeological Society. We thank the Stable Isotope Facility at UC Davis for running the analysis on the clam samples. Finally, we gratefully acknowledge the Ohlone people on whose land Alameda is located and the Patwin people on whose land UC Davis is built.

Disclosure Statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by Sacramento Archeological Society; Pacific Coast Archaeological Society.