Environmental Archaeology The Journal of Human Palaeoecology ISSN: 1461-4103 (Print) 1749-6314 (Online) Journal homepage: http://www.tandfonline.com/loi/yenv20 Shellfish Exploitation in the Western Canary Islands Over the Last Two Millennia Wesley Parker, Yurena Yanes, Eduardo Mesa Hernández, Juan Carlos Hernández Marrero, Jorge Pais, Nora Soto Contreras & Donna Surge To cite this article: Wesley Parker, Yurena Yanes, Eduardo Mesa Hernández, Juan Carlos Hernández Marrero, Jorge Pais, Nora Soto Contreras & Donna Surge (2018): Shellfish Exploitation in the Western Canary Islands Over the Last Two Millennia, Environmental Archaeology, DOI: 10.1080/14614103.2018.1497821 To link to this article: https://doi.org/10.1080/14614103.2018.1497821 View supplementary material Published online: 22 Jul 2018. Submit your article to this journal View Crossmark data Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=yenv20 ENVIRONMENTAL ARCHAEOLOGY https://doi.org/10.1080/14614103.2018.1497821 Shellfish Exploitation in the Western Canary Islands Over the Last Two Millennia Wesley Parkera, Yurena Yanesa, Eduardo Mesa Hernándezb, Juan Carlos Hernández Marreroc, Jorge Paisd, Nora Soto Contrerasa and Donna Surgee aDepartment of Geology, University of Cincinnati, Cincinnati, OH, USA; bDepartamento de Prehistoria, Antropología e Historia Antigua, Universidad de La Laguna, La Laguna, Tenerife, Canary Islands, Spain; cEl Museo Arqueológico de La Gomera, San Sebastián de La Gomera, La Gomera, Canary Islands, Spain; dMuseo Arqueológico Benahoarita, Los Llanos de Aridane, La Palma, Canary Islands, Spain; eDepartment of Geological Sciences, University of North Carolina, Chapel Hill, NC, USA ABSTRACT ARTICLE HISTORY The residents of the Canary Archipelago consumed limpets since the arrival of humans ∼2500 Received 26 February 2018 yrs. ago, and these harvested gastropods were deposited in large coastal shell middens. This Revised 11 May 2018 work preliminarily explores shell margin oxygen isotope composition (δ18O) and body size of Accepted 25 June 2018 the black limpet (Patella candei d’Orbigny, 1840) from archaeological sites in the Canary fi KEYWORDS Islands to assess possible seasonal variability and intensity of shell sh collection throughout Body size; oxygen isotopes; δ18 the late Holocene. The shell margin O values of 100 shells (radiocarbon dated between paleotemperature; Patella; ∼500 and ∼1800 cal. yr BP) were analysed to estimate sea surface temperature (SST) at time shell midden; Canary of death. Paleotemperature estimates suggest shellfish harvesting was not year-round, and Archipelago was avoided in the cooler months (when SST < 20°C). This pattern differs from most higher latitude Mesolithic and Neolithic human groups, which gathered shellfish year-round, targeting winter more heavily. Preliminary body-size measurements suggest shell sizes have experienced a decline from aboriginal times to the present, which possibly resulted from increasing anthropogenic pressures. During aboriginal inhabitation, maximum adult shell size remained stable, suggesting that present-day harvesting practices are more intense than harvesting from aboriginal human groups. This intensive collection has likely diminished the average adult size of limpet populations in the islands by ∼27%. Introduction of spawning (Burchell et al. 2013). Recent advances in Identifying the season of shellfish collection in archae- isotope sclerochronology, the study of the geochemical ological deposits has been the focus of extensive and physical information stored within the accretion- research over the past 30 years to better understand ary hard parts of organisms (Buddemeier, Maragos, how ancient humans interacted with their dynamic and Knutson 1974; Andrus 2011; Surge and Schöne environment (Kennett and Voorhies 1996; Hallmann 2015), have provided higher resolution and accuracy et al. 2009, 2013; Burchell et al. 2013; Kyriacou et al. in estimating season of collection through the develop- 2015; Thomas 2015). Moreover, archaeological mollusc ment of oxygen isotope profiles throughout the lifespan size has been used as a proxy for intensity of harvesting of molluscs (Mannino and Thomas 2001; Mannino, practices and to assess ecological response to resource Spiro, and Thomas 2003; Fenger et al. 2007; Mannino exploitation by humans (Milner, Barrett, and Welsh et al. 2007; Mannino and Leng 2008; Colonese et al. 2007; Genner et al. 2010; Klein and Steele 2013). 2009; Hallmann et al. 2009, 2013; Andrus 2011; Together, understanding the intensity and seasonality Wang, Surge, and Mithen 2012; Burchell et al. 2013; of shellfish exploitation helps to constrain the impacts Surge et al. 2013; Wang, Surge, and Walker 2013). and responses of ancient humans and their environ- The shell margin, which represents the last growth epi- ments throughout human history. sode of a shell, closest to organisms’ death, contains an Early studies on the season of shellfish collection isotopic ‘snapshot’ of the sea surface temperature (SST) have used growth lines only – which are produced closest to the time of death. This approach can inform both annually and seasonally – to identify the season if shells were collected throughout the year or were pre- of collection by differentiating between growth lines ferentially collected during specific months or seasons. that may have formed during warm or cold periods Many recent studies on the season of shellfish collec- (Coutts 1970; Claassen 1983; Milner 2001). This tion analyse at least 3-5 samples collected at ∼2– method, however, is prone to error because growth 3 mm intervals from the growth margin towards the lines can be produced by non-temperature stressors apex (Jew et al. 2013, 2014). This method of isotopic such as changes in salinity, turbidity, or even the stress analysis provides greater clarity into warming or CONTACT Wesley Parker [email protected] Department of Geology, University of Cincinnati, Cincinnati, OH 45221, USA Supplemental data for this article can be accessed at https://doi.org/10.1080/14614103.2018.1497821 © Association for Environmental Archaeology 2018 2 W. PARKER ET AL. cooling trends, allowing for a relatively accurate are likely to have remained relatively consistent in characterisation of the season of shellfish harvest. the Canary Islands over the last two millennia, due to While shell margin isotopic data cannot be used to their low-latitude location and absence of inflowing determine the exact season of harvest (e.g. spring and freshwater sources, studies conducted in these fall seasons are difficult to discriminate), it does pro- locations are expected to be primarily influenced by vide a cost-effective, useful dataset that can be used human-mollusc interactions (Mann and Jones 2003; to preliminarily assess if shellfish were collected year- Lebreiro et al. 2006). Modern populations in the Can- round or not (Parker et al. 2017). This determination ary Islands are one of the few remaining human groups can then form the basis for ongoing, high-resolution that continue to utilise limpets as a major dietary isotope sclerochronological study. staple. Therefore, human-mollusc interactions for gas- A recently published modern calibration study con- tronomic purposes are not limited to the archaeological ducted in the Canary Islands demonstrated that the oxy- record in the Canary Islands, but rather are an ongoing gen isotope ratios of the last growth episode (shell process continuing to the present. margin) of Patella candei d’Orbigny, 1840 can be cred- In this study, we investigate 10 well-preserved and ibly used as a paleothermometer in the archipelago (Par- physically accessible shell middens from 3 of the 7 Can- ker et al. 2017). This study, however, found that ary Islands of Spain: Tenerife, La Palma and La P. candei δ18O values were 1.3 ± 0.2‰ higher than Gomera (Figure 1(B)). There are three primary objec- expected when compared to predicted values if the tives to this study. First, we determine the ages of 10 organism precipitated its shell in isotopic equilibrium. archaeological sites using AMS radiocarbon dating on This isotopic offset resulted in estimated SSTs that the shells themselves, providing the first numerical were, on average, 5.7 ± 0.6°C lower than observed values ages for most of the studied sites. Second, we analyse if not corrected. However, because the vital effect is uni- the oxygen isotope composition of the shell margin form and predictable, it can be corrected by subtracting of archaeological P. candei to produce an exploratory 1.3‰ from the measured shell δ18O value. Similar dataset of the temperatures closest to the time of offsets have been documented in other Patella species shellfishing practices, which will subsequently form that serve as archives of SST (Shackleton 1973; Cohen the basis for ongoing and future high-resolution sea- and Tyson 1995; Fenger et al. 2007; Wang, Surge, and sonality studies throughout the archipelago. Third, Mithen 2012; Surge et al. 2013; Gutiérrez-Zugasti et al. we attempt to assess the intensity of shellfishing prac- 2017; Prendergast and Schöne 2017). The adjusted tices, and their long-term ecological impacts, through temperatures from the shell coincided well with the analysis of changes in body size through a time of observed SST in the study area during the time of collec- modern and archaeological adult specimens. tion. Accordingly, archaeological P. candei shells from There are two driving hypotheses for this