The growth rings of clam shells from two pentlatch middens as indicators of seasonal gathering
Date
1976
Authors
Keen, Sharon Denise
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Abstract
Until recently, there have not been effective or reliable techniques that enabled archaeologists to infer site seasonality or seasonal resource usage from their data. This has been a major problem in the reconstruction of Gulf of Georgia prehistoric ways of life for although the ethnographic record at the time of contact is reasonably clear on the seasonal nature of subsistence activities it has been very difficult to ascertain how far into the past these economic patterns existed. As many shellfish fauna now have been found to exhibit different anatomical characteristics in their growth rings at specific times of the year, and as shellfish, such as clams, are frequently more common and more easily sampled in archaeological strata than are other vertebrate seasonal markers, this study attempted to use clam remains from two Pentlatch middens to help reconstruct patĀterns of seasonal clam resource usage for the northern Gulf of Georgia area. Northwest Coast ethnographic shellfish gathering data were reviewed and, from this information a hypothesis was constructed regarding the likely seasons of clam exploitation at the Tsable River Bridge and Buckley Bay sites. In order to test the hypothesis, growth increments beyond the last winter ring before death were measured on midden bivalves and then compared to the average annual growth increases of recent clams that were the same species and age at death. Gathering seasons were then inferred for the midden clams as the annual growth increases for the various beach clam species had been divided into four quarters that corresponded to certain seasons. In many of the natural strata the seasonal clamming pattern that prevailed was Salishan in nature: some gathering was done year-round, but most gathering was done in the summer months with a lesser amount in the spring period. Chi-square figures calculated for the larger of these distributions from the various strata indicated that they were significant (.05-.001). This seasonal patterning of clam gathering also seemed to remain virtually unchanged through time in the excavation units of both sites. In terms of the species being exploited, both butter clam and littleneck were present in virtually every season. Rock cockle was present in most matrices as well but sampling difficulties due to breakage made it difficult to deterĀmine in which seasons it had been taken.