ASSESSING THE INTENSITY OF SHELLFISH EXPLOITATION FROM PRE-HISTORIC TO RECENT TIMES IN THE CANARY ISLANDS

Shellfisheries are a relevant resource and an important economic endeavor to coastal and islands regions, but past and present shellfish exploitation has challenged their sustainability. The residents of the volcanic and oceanic Canary Archipelago have exploited and consumed limpets since the first arrival of humans ~2,000 yrs ago. The potential negative impacts of prehistoric to recent marine human exploitation have not been assessed in this region, even though limpets are an important part of the economy and gastronomy of these islands. This study assesses the degree of human harvesting practices of limpet populations from three western Canary Islands (Tenerife, La Palma, La Gomera) since pre-Hispanic times to recent by examining temporal variations in limpet body size. The size (length, width and height) of the dominant and most harvested species, Patella crenata, was measured from ten radiocarbon-dated shell middens and compared to live-collected specimens. Increased human harvesting practices consistently results in reduced shell size because the most edible (larger, older) mollusks are more intensively collected, which, in turn, diminishes turnover rates due to resource depression. Limpet shell size varied throughout the last 2,000 years, with a major predation intensity detected at ~970 cal yrs BP. Interestingly, the size of all archeological limpets from all time-periods and islands were significantly larger than living specimens in the region. The results suggest that although pre-Historic human groups appear to have somewhat impacted this marine resource, present-day harvesting practices are more intense than previously thought. Although climate change could be in part responsible for the observed temporal changes in limpet size, the target record comprises the last 2,000 yrs and therefore, variations in local climate are expected to be minimal in this low-latitude oceanic region.