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

The residents of the Canary Archipelago consumed limpets since the arrival of humans similar to 2500 yrs. ago, and these harvested gastropods were deposited in large coastal shell middens. This work preliminarily explores shell margin oxygen isotope composition (delta O-18) 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 delta O-18 values of 100 shells (radiocarbon dated between similar to 500 and similar to 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 degrees 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 similar to 27%.