Making the most of fragments: a method for estimating shell length from fragmentary mussels (Mytilus californianus and Mytilus trossulus) on the Pacific Coast of North America Gerald G. Singh a , Iain McKechnie b, c, * a Institute for Resources, Environment and Sustainability, University of British Columbia, Vancouver, BC V6T 1Z4, Canada b Department of Anthropology, 308 Condon Hall, University of Oregon, Eugene, OR 97403, USA c Department of Archaeology, Hakai Institute, Simon Fraser University, Burnaby, BC V5A 1S6, Canada article info Article history: Received 8 December 2014 Received in revised form 17 February 2015 Accepted 18 February 2015 Available online 26 February 2015 Keywords: Archaeomalacology Marine ecology Dietary reconstruction Morphometric regression Historical ecology Zooarchaeology Northwest Coast abstract California mussel (Mytilus californianus) are ubiquitous shellfish species in coastal archaeological sites throughout western North America but are often highly fragmentary when recovered in small-volume ‘column’ or ‘bulk’ samples typically used to quantify shellfish assemblages. Archaeological research has predominantly focused on evaluating the dietary contribution of Mytilus but most studies assume an average meat weight or use categorical size classifications to determine subsistence strategies and harvest profiles. In this paper, we develop and evaluate a regression-based method for estimating shell length and meat weight for fragmentary Mytilus remains. Our regressions are based on live-collected M. californianus specimens from multiple locations in California and British Columbia and provide consid- erable statistical confidence for predicting length and meat weight. We also apply the same regressions to a collection of Mytilus trossulus and show similar predictive equations, indicating this method can be used in cases where it is not possible to distinguish morphologically between M. californianus and M. trossulus. We demonstrate how these results improve upon previous size-classification methods and discuss the potential for applying these measurements to enhance the relevance of these zooarchaeo- logical data for modern marine conservation and management efforts. © 2015 Elsevier Ltd. All rights reserved. 1. Introduction The California mussel (M. californianus) is a ubiquitous and protein rich shellfish species found in archaeological sites throughout the coast of western North America (e.g., Braje et al., 2007; Erlandson, 1988; Losey and Power, 2005; Porcasi, 2011; Sumpter, 2005). Mussels are present from the mid-to lower inter- tidal on wave-exposed rocky coasts from Alaska to Baja California (Schmidt, 1999; Suchanek, 1979). Judging from the ubiquity and abundance of M. californianus in coastal archaeological assemblages as well as numerous ethnographic accounts of it use, this species was a widely valued marine food regularly harvested and consumed by coastal indigenous people throughout the Holocene (Braje et al., 2012; Ellis and Swan, 1981; Erlandson et al., 2008; Jones and Richman, 1995; Whitaker, 2008). Mussels are consid- ered ‘ecosystem engineers’ in intertidal ecosystems, providing habitat for many invertebrates and outcompeting intertidal sea- weeds (Menge et al., 1994; Paine, 1974). M. californianus can be long-lived (>20e50 years) and grow to large sizes (over 20 cm in length) and thus can be overharvested by humans (Seed and Suchanek, 1992). Ecologically, M. californianus populations respond to a variety of factors such as climate and oceanography (Menge et al., 2008; Smith et al., 2006), temperature (Ford et al., 2010; Harley, 2011), and intertidal predation by other marine predators such as sea stars (Pisaster sp.) and sea otters (Enhydra lutris)(Menge et al., 1994; Singh et al., 2013). Given the ecological and economic importance of mussels, further investigation into the characteristics of archaeological assemblages has the potential to enrich understanding of coastal adaptations, humaneenvironment interactions, and paleoecology. Coastal archaeologists have a long history of investigating archaeological shellfish assemblages to detect nutritional, cultural, and ecological patterns and changes over time (Cook, 1946; Moss, * Corresponding author. Department of Anthropology, 308 Condon Hall, Uni- versity of Oregon, Eugene, OR, 97403, USA. E-mail addresses: geraldsingh@gmail.com (G.G. Singh), iainm@uoregon.edu (I. McKechnie). Contents lists available at ScienceDirect Journal of Archaeological Science journal homepage: http://www.elsevier.com/locate/jas http://dx.doi.org/10.1016/j.jas.2015.02.029 0305-4403/© 2015 Elsevier Ltd. All rights reserved. Journal of Archaeological Science 58 (2015) 175e183