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Archaeological sites represent long-term biological repositories, relevant for understanding ancient economies and ways of life that can provide historical baseline data for contemporary conservation biology, restoration ecology, and fisheries management. Small-scale excavations at nine archaeological sites within Point Reyes National Seashore, on the central California coast, led to the recovery of a large assemblage of fish remains from deposits dated from 800 to 770 cal BC to the historical era. These assemblages contained over 9000 fish remains identified to at least a family. Applying quantitative analysis and morphometric studies, these data suggest the indigenous fishery of Point Reyes in the homeland of the Coast Miwok people was directed toward the acquisition of mass-captured forage fish from the families Clupeidae, Atherinopsidae, and Engraulidae in addition to Embiotocidae. Perceived declines in contemporary forage fish populations within Point Reyes National Seashore, specifically Pacific herring (Clupea pallasii), an important keystone, indicator, and umbrella species, suggest further protections are needed to ensure continued ecosystem services and prevent ecological extinction.

A new method developed by Schweikhardt et al. (2011) for the geochemical analysis of bay mussels is applicable (when combined with radiocarbon assessments) for examining the seasonal construction patterns and growth cycles of coastal mound sites over time. Ideally suited for the analysis of mollusk fragments in museum collections, this method allows archaeologists to evaluate divergent models about the functions of mound sites, as well as the mobility practices and social organizations of the mound builders. In this case study, the method is employed to examine two adjacent mounds (Ellis Landing, Brooks Island) in the San Francisco Bay Area, California to assess whether their occupants may have participated in a broader multi-site community dating to the Late Period (1100–250 BP).

Seasonal patterns of Native American residence and use of shell mounds of the San Francisco Bay area, California are of great interest. This work investigates seasonal occupation by means of a new method for interpretation of geochemical data from Mytilus trossulus specimens recovered from one of these structures, the Ellis Landing Shell Mound (CA-CCO-295). The approach, which is suitable for relatively small shell fragments from a variety of archaeological contexts, is used to infer the environmental conditions (temperature and salinity of ambient water) at harvest time, compared with average conditions for the period, and thus estimate the season during which the shells were harvested. This information, in turn, is employed to evaluate current models about the growth and construction of prehistoric shell mounds in San Francisco Bay. The method was applied to seven different lenses in the shell mound ranging in age from ∼240 cal yr BP to ∼3510 cal yr BP. We found that, although seasonal occupation varied over time, it generally was confined to summer through late fall, with little indication of winter gathering. Our findings suggest that California shell mounds, such as Ellis Landing, were constructed in a very different manner than some other mounded places used by contemporaneous hunter-gatherers elsewhere in North America.