3500 years of shellfish mariculture on the Northwest Coast of North America

Abstract

Ancient systems of mariculture were foundations of social-ecological systems of many coastal Indigenous Peoples. However, since such systems either do not leave tangible remains in the archaeological record, and/or are hard to date, we know little about their development and use. Clam gardens, traditional mariculture features located within the intertidal zone along the Northwest Coast of North America, are composed of a rock wall positioned at the low tide mark and a flattened terrace on the landward side of the wall. Because these features are largely composed of rock and sediment, and have complex formation histories, they can be difficult to age. On northern Quadra Island, British Columbia, we identify three variations in clam garden form, constructed in different geomorphological settings, each of which require different sampling approaches to obtain ages on construction and ongoing use. To age the clam gardens, we consider radiocarbon dating of invertebrates that inhabit beach deposits (both pre- and post-garden construction), and the relationship of the gardens and clam samples to the local sea level history and taphonomic processes. Within our study area, we find clam gardens have been in use for 3500 years, likely corresponding to other social and ecological changes of the time. These data allow us to formulate guidelines on samples most suitable to constrain the age of initial and on-going wall construction and use of clam gardens, which can be extrapolated to dating other ancient mariculture features in other regions. Such dating programs are the foundation for understanding the long-term development of traditional marine management practices and how they are situated in broader social-ecological systems.

11,500 y of human–clam relationships provide long-term context for intertidal management in the Salish Sea, British Columbia

“…After ∼3.5 ka, human–clam relationships in our study area intensify as indicated by the building of some of the first clam gardens (24). At this time, large settlements increase in number in Kanish and Waiatt Bays, filling all inhabitable coastal landforms and reflecting an increase in local human populations.…”

“…Many large villages established at that time continued to be occupied until the late 1700s CE, at which time European diseases severely decreased Indigenous populations (25). Clam gardens were first constructed at some time around 3.5 ka, and they continued to be built and maintained, although in a much reduced way, into the mid-1900s (24). The number and extent of shell midden sites and the density of clam garden features (Fig.…”

“…In our study sites in Kanish and Waiatt Bays, the coevolved history of humans and clams is reflected in the expansive archaeological shell middens with deposits dating to as old as 9 ka and the plethora of clam gardens dating from sometime after 3.5 ka (Fig. 1) (24).…”

Saving the planet with appropriate biotechnology: 2. Cultivate shellfish to remediate the atmosphere

“…The antiquity of this technology is truly prehistoric, meaning that there is no written tradition relating to it, but there is an aural tradition which is conserved by present day First Nations peoples, some of which can be found in the YouTube videos listed in Table 4. This coastal engineering activity, called clam gardens by western science, has played a significant role for many millennia in First Nations communities of the Pacific Northwest; certainly, for up to 11,500 years (Smith et al, 2019;Toniello et al, 2019). However, most of the gardens have not been tended for many decades and are in need of restoration.…”

Shellfish subsidies along the Pacific coast of North America

“…These intertidal rock walls and associated terraces represent one of several coastal habitat alterations created over millennia by Coast Salish people to steward marine resources, increase clam productivity and ensure stable shellfish abundances adjacent to coastal communities to support economies, cultural practices and governance (Lepofsky et al 2015, Hul'q'umi'num -GINPR 2016. Recent radiocarbon dates and scientific investigations into taphonomic processes, indicate clam garden construction throughout Northern Quadra Island, British Columbia, began at least 3500 yr before present (Smith et al 2019). In addition to supplying a reliable food source for communities, clam gardening is integral to governance systems that dictated land use and stewardship, which continues to the present day (Deur et al 2015, Lepofsky et al 2015, Hul'q'umi'num -GINPR 2016.…”