Abstract
Shellfish have supported Indigenous lifeways on the Pacific Coast of North America for millennia. Despite the ubiquity of clamshells in archaeological sites, shell size measurements are rarely reported due to a lack of applicable basis for generating size estimates from fragmentary remains. We present a linear regression-based method for determining shell length from hinge and umbo measurements of littleneck (Leukoma staminea; n = 239), butter (Saxidomus gigantea; n = 274), and horse (Tresus nuttallii; n = 92) clams using both contemporary and archaeological shells collected from three regions in coastal British Columbia, Canada. We examine the accuracy of these size estimations, which indicate that 83%–97% of the variability in dorsal shell length is predicted by umbo thickness and hinge length. Hinge length generated higher R2 values yet exhibited greater intra- and inter-observer error. While the predicted dorsal length for each species differed by region, this size difference was smaller than intra- and inter-observer error, suggesting broad applicability for these simple measurements. We applied these formulae to a Tseshaht First Nation archaeological clamshell assemblage (n = 488) on western Vancouver Island spanning 3000 years and observed profiles that resemble contemporary legal size limits, which suggests the sustained use and maintenance of local shellfisheries. The accuracy of these regression models for determining shell length from fragments highlights the utility of this approach as a basis for assessing past shellfish management practices.
Introduction
Information emerging from research in archaeology and historical ecology, as well as work with traditional knowledge holders on the Pacific Coast of North America, indicate that Indigenous peoples have had an active role in managing terrestrial, coastal, and aquatic ecosystems over millennia (Deur 2005; Moss 2011; Mathews and Turner 2017). Such research highlights a diverse and well-established set of stewardship practices informed by Indigenous knowledge, including size-selective fishing technology, plant and shellfish cultivation, rights-based harvesting restrictions, and ceremonial controls that enhanced the productivity and availability of numerous habitats and resources (Deur 2005; Haggan et al. 2006; Turner and Berkes 2006; Menzies and Butler 2007; Moss 2011; Lepofsky et al. 2015). The occurrence and persistence of these Indigenous resource management practices contributed to the resilience of coastal marine ecosystems, which challenge notions of Indigenous peoples as “hunter-gatherers” or “fisher-hunter-gatherers” (Deur and Turner 2005; Moss 2011). The ongoing legacies of these sustained and intentional activities are being further examined through community-oriented research projects that draw together a variety of techniques and knowledge sources, including archaeological data, with the aim to restore ecosystem function as well as revitalize relationships between people and marine foods (Augustine and Dearden 2014; Hatch et al. 2023).
Shellfish are among the most prolific and ubiquitous evidence of edible foods encountered in archaeological sites throughout the Northwest Coast (Moss 2013). Several species of clam and mussel commonly occur, with littleneck (Leukoma staminea), butter (Saxidomus gigantea), and horse (Tresus nuttallii) among the most prominent bivalves. These burrowing intertidal animals occur in soft sediments (i.e., mud, sand, gravel, and mixed substrates) and are harvested as a reliable and nutritious source of food extending back to some of the earliest documented settlements in the region that have preserved evidence (e.g., Fedje et al. 1996; Cannon et al. 2008; McLaren et al. 2011; Toniello et al. 2019). As documented in ethnographic accounts and oral histories, clams have key cultural significance (Moss 1993, 2013; Deur et al. 2015) in addition to their important role in local economies and food systems (Ellis and Swan 1981; Deur et al. 2015). This emphasis is consistent with archaeological evidence, where massive quantities of clams and other invertebrate species occur in “shell midden” deposits observed throughout the coast. Landforms composed of abundant shell have also been interpreted as monumental landscape features, where previous harvests are purposefully used as geoengineering material, altering coastal geomorphology, and shoreline configurations (Blukis Onat 1985; Grier et al. 2017; Letham et al. 2020). Archaeological investigations into past shellfish harvesting locations, coupled with traditional knowledge and ecological science, have demonstrated the enduring use of intertidal “clam garden” features. Clam gardens are cleared beaches with rock-wall terraces built at low tide, which elevate the beach and trap sediment thereby increasing clam habitat, growth and productivity, harvesting accessibility, and help ensure food security for coastal communities (Groesbeck et al. 2014; Lepofsky et al. 2015; Jackley et al. 2016; Lepofsky et al. 2021).
