UC Davis

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.