Estimating Crown Conch (Melongena Corona)
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Journal of Archaeological Science: Reports 21 (2018) 107–116 Contents lists available at ScienceDirect Journal of Archaeological Science: Reports journal homepage: www.elsevier.com/locate/jasrep Estimating crown conch (Melongena corona) tissue weight from archaeological shell measurements: An allometric methodology for coastal T historical ecological research ⁎ Kendal Jacksona, , Elizabeth Southarda, Sharlene O'Donnellb, John Arthurc a Department of Anthropology, University of South Florida, Tampa, USA b Department of Anthropology, University of Florida, Gainesville, USA c Department of Society, Culture, and Language, University of South Florida, St. Petersburg, USA ARTICLE INFO ABSTRACT Keywords: Coastal archaeologists and historical ecologists are taking an increasingly robust interest in marine shell as- Experimental zooarchaeology semblages recovered from coastal villages and civic-ceremonial sites. These assemblages must be quantified Florida Gulf Coast before archaeologists can make assessments of biomass flows and subsistence contributions. We present the Invertebrate allometry results of an experimental allometric study on Melongena corona snails collected from the mangrove dominated Marine shell shoreline of Weedon Island Preserve, Florida, USA. Our analysis produced regression constants for predicting tissue weight estimates from four independent linear shell metrics, including: length, aperture-length, height, and width. This study is unique in its integration of field and laboratory experimentation, and in the large sample size used to develop allometric constants. To exemplify the utility of our regression models, we apply our al- lometric constants to a late-Precolumbian (ca. 895–1268 CE) marine shell assemblage excavated from the Weeden Island site (8PI1), Pinellas County, Florida, USA. 1. Introduction averaged meat weight predictions to reflect variation in sex, age, and size differences (Lyman, 1979; Reed, 1963; Smith, 1975; Ziegler, In recent years, archaeologists have begun to take an increased 1973). However, in utilizing average values and MNI, these attempts interestintheroleofmarineshellfish in the subsistence strategies, share the fundamental flaws inherent in White's (1953) approach – an settlement architecture, and sociopolitical lives of coastal fisher- assumption that the dimensions of the bone or shell element being hunter-gatherer societies (Erlandson et al., 2008; Keegan et al., 2003; measured relate to meat weight at a constant (i.e., linear) ratio (Reitz Lulewicz et al., 2017; Marquardt and Kozuch, 2016; Onat, 1985; et al., 1987:305), and that MNI may not be comparable across taxa or Trubitt, 2005; Walker, 2000). To understand the dietary contributions across depositional contexts (Thomas and Mannino, 2017). Indeed, of particular taxa and map-out energy flows between near-shore linear surface area metrics and volumetric variables such as meat ecosystems and human communities, zooarchaeologists must quantify weight relate to each other in exponential terms and may be described mollusk-shell data via estimates of tissue weight (i.e., “meat weight”), by the equation y = axb where: y is meat weight, x is the linear biomass, and/or kilocalories (Perez, 2010; Reitz et al., 1987; Reitz and measurement, and a and b are constants that define the relationship Wing, 2008). Indeed, research by Thomas and Mannino (2017) has between these variables (Gould, 1966). Our study presents allometric demonstrated that meat weight values may be critical to properly regressions developed from experimental collection and analyses on understanding relative taxonomic abundance for various mollusks in 305 Melongena corona snails collected along a mangrove-dominated archaeological assemblages (also see Claassen, 2000). Early ap- shoreline site in Tampa Bay, Florida, USA, between 2011 and 2013. proaches to this problem – based on the work of White (1953) – We report new experimentally derived constants for calculating tissue multiplied average meat weight parameters by minimum number of weight estimates from four archaeological shell metrics: length, individuals (MNI) values to calculate the estimated total meat weight aperture-length, width, and height. We then apply our equations to for a particular taxon in a given assemblage. Subsequently, several zooarchaeological assemblages excavated from the Weeden Island site attempts have sought to improve upon White's method by modifying (8PI1), a large (> 2 km2), multi-component, coastal village and ⁎ Corresponding author at: 4202 E. Fowler Ave. SOC 107, Tampa, Florida 33620, USA. E-mail address: [email protected] (K. Jackson). https://doi.org/10.1016/j.jasrep.2018.07.004 Received 20 March 2018; Received in revised form 5 July 2018; Accepted 6 July 2018 2352-409X/ © 2018 Elsevier Ltd. All rights reserved. K. Jackson et al. Journal of Archaeological Science: Reports 21 (2018) 107–116 Fig. 1. Location of experimental harvesting site, Weedon Island Preserve, Florida. ceremonial center on the western shore of Tampa Bay, Florida Further, activity patterns among crown conch are seasonal; in winter (Weisman et al., 2005). they are relatively inactive and remain entirely or partially buried in the sand or mud substrate. In summer they are more active and achieve 2. Background the vast majority of their growth. Fisher-hunter-gatherer communities on Florida's Gulf Coast col- Crown conch snails (Melongena corona) are predatory marine gas- lected M. corona and other estuarine gastropods as an important faunal tropods found in particular abundance on the Gulf Coast of Florida, but resource from onset of highly-productive estuarine conditions during also found on the eastern coast of Alabama, in the Yucatan, and along the Mid-Holocene through the protohistoric era (e.g., Duke, 2015; the Atlantic Coast of Florida and Georgia (Bowling, 1994; Pilsbry and Mikell and Saunders, 2007; Defrance and Walker, 2013). Their shell Vanatta, 1934). They inhabit low-energy intertidal environments (i.e., remains are relatively ubiquitous within invertebrate faunal assem- sand and mud flats, marshes, and oyster bars) with moderate-salinity blages from village and mound sites along the Gulf Coast where mod- conditions (12–15%) and become inactive at salinities below 9% erate salinities predominate (Vojnovski, 1995; Defrance and Walker, (Hathaway and Woodburn, 1961). Crown conchs range in size generally 2013; Walker, 1992); they are also present within shell-bearing as- between 10 and 110 mm in length; larger individuals more typically semblages along the Atlantic coasts of Florida and Georgia (Claassen, inhabit eastern oyster (Crassostrea virginica) reefs, while juveniles dis- 1986; Reitz, 1988). In some sub-regions, for instance on Florida's Big proportionately occupy intertidal sand or mud flats and marshes Bend marsh coast, crown conch shells may have been collected prin- (Bowling, 1994). They are most active at high tide during feeding; cipally for tool manufacturing (Blankenship, 2013; Duke, 2015; O'Neal, crown conch are both scavengers and predators, feeding on bivalves, 2016). In other areas, such as Florida's Central Gulf Coast - encom- other gastropods, and various estuarine detritus (see Turner, 1959). passing Tampa and Sarasota Bays - this species makes up a substantial 108 K. Jackson et al. Journal of Archaeological Science: Reports 21 (2018) 107–116 Fig. 2. Collecting crown conch within the experimental harvesting site, Weedon Island Preserve, Florida. Photo by Elizabeth Southard. portion of the invertebrate faunal count, suggesting that it may have (y = axb)toinfluence regression constants. Results suggested that large been a major subsistence resource comparable to eastern oyster (Cras- sample sizes are important, and that intermediate-sized snails (those sostrea virginica)(Janus Research, 2004; O'Donnell, 2018: in press; approximating average size) are predisposed to introduce much of the Quitmyer, 2002; Vojnovski, 1995, 1998). For example, O'Donnell residual error within allometric regressions, decreasing coefficient of (2018:in press) analyzed zooarchaeological assemblages from a shell determination statistic (R2) values (Reitz et al., 1987:309; also see midden at the Weeden Island site (8PI1) and found that crown conch Peters, 1983:28). We aim to build upon this foundational work by: (n = 1329) makes up nearly 26% of the total invertebrate MNI count collecting experimental specimens across a range of estuary conditions, (n = 5254) and ranks second only to oyster (n = 1846). considering a larger sample size (n = 305), and developing in- We follow Claassen (1998) in taking caution against the normative dependent allometric models for four distinct shell metrics, such that assumption that archaeological shells unequivocally represent food tissue weight may be estimated from incomplete (fragmentary) and/or debris; in her words: “evidence of collection and preparation [of ar- modified shell specimens. chaeological shellfish] does not equal consumption” (Claassen, 1998:285; also see Waselkov, 1987:166). Indeed, work by Onat (1985) on the Northwest Coast and by a growing school of Florida archae- 3. Experimental methods ologists (e.g., Pluckhahn et al., 2016; Schwadron, 2017; Sassaman et al., 2017) has irreparably deconstructed ‘shells-as-garbage’ hypotheses by After recognizing that M. corona shells make-up the majority (some demonstrating that coastal Precolumbian foragers planned and rapidly 55%) of gastropod assemblages within midden excavation blocks at the Weeden Island site (O'Donnell, 2018: in press),