Historical voyages, tourist souvenirs and the fate of the endemic mollusc fauna of Rapa Nui

Abstract

Rapa Nui, also known as Easter Island, is the most geographically isolated island on Earth. This isolation has led to high endemism, which is 35-40% for molluscs. In addition to its biological uniqueness, Rapa Nui has a unique human history, as it has been inhabited for over 1000 years. During this time,populations have oscillated between about 15,000 to a few hundred inhabitants in the late 1800s. Close to 8,000 people now live on the island where tourism provides the majority of the population?s income. As a result, benthic resources such as molluscs are intensively harvested (at least since the 1970s) to be sold as souvenirs. The presence of endemic molluscs from Rapa Nui has been documented by naturalists on historical voyages since the early 1900s. However, our recent sampling of shell assemblages from six sites around the island revealed that some of these species (e.g. Cypraea caputdraconis or ?pure?) are missingfrom current communities. The only trace we found of them was as jewelry in souvenir markets. To understand if the absence of these species from assemblages is due to overharvesting, we hypothesized that the molluscs from dead shell assemblages would be significantly smaller than the ones collected duringhistorical voyages when the human population was much smaller. We measured the size of 13 species of gastropods abundant both in our samples and in the collections at the National Museum of Natural History (Smithsonian Institution). Half of these species are currently used for jewelry and the other half do notseem to be exploited. Our results will allow us to determine if harvesting pressure from the local souvenir industry is affecting the size of shells, making them smaller than they were in the past. These findings willalso inform natural resource managers of Rapa Nui about the current state of the endemic mollusc fauna, hopefully leading to education of the local community on the importance of protecting their unique resources.