Shellfish Exploitation in the Western Canary Islands Over the Last Two Millennia

Abstract

The residents of the Canary Archipelago consumed limpets since the arrival of humans ∼2500 yrs. ago, and these harvested gastropods were deposited in large coastal shell middens. This work preliminarily explores shell margin oxygen isotope composition (δ 18 O) and body size of the black limpet (Patella candei d'Orbigny, 1840) from archaeological sites in the Canary Islands to assess possible seasonal variability and intensity of shellfish collection throughout the late Holocene. The shell margin δ 18 O values of 100 shells (radiocarbon dated between ∼500 and ∼1800 cal. yr BP) were analysed to estimate sea surface temperature (SST) at time of death. Paleotemperature estimates suggest shellfish harvesting was not year-round, and 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%.

Dietary changes across time: Studying the indigenous period of La Gomera using δ13C and δ15N stable isotope analysis and radiocarbon dating

“…However as seen in our baseline table (Table 6), marine mollusks and plant‐eating fish (such as the Sparisoma cretensis ) have low nitrogen values. These sources were undoubtedly part of the diet of the indigenous population of the island, although they were probably a sporadic, seasonal resource, as established in recent studies (Mesa Hernández et al, 2010; Parker et al, 2018). Prehistoric populations which mostly consumed marine resources have nitrogen values well above our mean values (White et al, 2020).…”

“…Paleoclimatic studies using stable oxygen isotopes have proven that climatic events that affected the northern hemisphere could have also altered the temperatures in the Canary Islands. One of these events is the Vandal Minimum, a cold event happening in between 1200 and 1400 BP, which has been recently confirmed to substantially drop the temperatures of the marine waters surrounding the islands at that time (Parker et al, 2018).…”

Scale of time-averaging in archaeological shell middens from the Canary Islands

“…Canarian shell middens are composed primarily of shells from the genus Patella Linnaeus, 1758 (Gastropoda: Patellidae), including Patella candei d'Orbigny, 1840 and Patella aspera Röding, 1798 (Figure 2c). These organisms, known commonly as limpets, inhabit the rocky intertidal region of the near-shore environment and have been a critical protein source for the Canary Islands from antiquity to the present (Mesa Hernández, 2006;Parker et al, 2018). The taxonomy of several species of Patella, including P. candei used in this study, has been a topic of some contention.…”

“…Archaeological remains are often used to study paleoclimate dynamics, ancient human behavioral patterns, temporal shifts in ecological niches, and paleoenvironmental change (e.g. Andrus, 2011;Burchell et al, 2013b;Colonese et al, 2009;Langejans et al, 2012;Maca-Meyer et al, 2004;Mannino and Thomas, 2001;Parker et al, 2018); yet natural and anthropogenic processes could significantly alter the temporal structure of these deposits, from single-use sites to multicentennial scale deposits, thus complicating interpretations drawn from these sites.…”

“…Shell middens often exhibit high-quality preservation of remains because of shelter from destructive natural forces like wave and wind energy, and high pH soil levels that slow down the decay process (Andrus, 2011). Moreover, shell middens are powerful archaeological tools, as they can help scientists to reconstruct ancient human harvesting patterns, prey handling processes, taphonomic conditions, paleoecology and ecosystem health, paleoclimatic context, and so on (Andrus, 2011;Burchell et al, 2013a;Colonese et al, 2009;Hausmann and Meredith-Williams, 2017;Mannino et al, 2007;Parker et al, 2018;Prendergast et al, 2016). Interpretations of these physical data could be significantly strengthened if time-averaging was adequately constrained within these sites.…”