See more from this Division: Topical Sessions
See more from this Session: Geochemical and Geoarchaeological Analysis of Shell Middens: Climate, Ecology, and Culture
Abstract:
Modern shells collected alive on a monthly basis for a period of one year from Pender Island, southern BC, were analyzed to determine the life history traits of this species (timing of growth line formation, duration of growing season, growth rate etc.). Oxygen isotope analysis confirms the seasonal variation in growth increment formation, with the most positive δ18O values of -0.37 associated with winter line formation (annual growth lines), and negative values (on average, -3.13) with more rapid warm-temperature growth. Intra-annual increments show clear seasonal oscillations with broadest increments (age four: 137µm) in summer and very narrow increments (age four: 6µm) or a growth cessation during winter months. A fortnightly pattern of microincrement width identified by frequency analysis suggests a diurnal periodicity in formation of intra-annual increments.
This research provides new insights into the biology and seasonal growth cycles of the butter clam, which is crucial information for interpreting the season of shellfish collection and paleotemperature. Biological and local environmental factors must be taken into consideration when using this species to determine patterns of seasonal shellfish collection in the archaeological record.
See more from this Division: Topical Sessions
See more from this Session: Geochemical and Geoarchaeological Analysis of Shell Middens: Climate, Ecology, and Culture