An analysis of weapons made from shark teeth and used by 19th century residents of the Gilbert Islands (Republic of Kiribati, Central Pacific) has revealed two species of sharks no longer native to the islands.
An example of a Gilbertese shark tooth weapon (Drew J et al)
Sharks were culturally important to the Gilbertese Islanders – historic records indicate a complex ritual system surrounding shark fishing and making fishing gear and weapons from shark teeth.
Scientists led by Dr Mark Westneat from the Field Museum of Natural History in Chicago analyzed a collection of 120 of these weapons, including some that resemble clubs, daggers, lances, spears and swords.
They identified eight species of sharks based on the teeth used in these weapons, two of which – the spot-tail shark (Carcharhinus sorrah) and the dusky shark (C. obscurus) – have never been reported from these waters, in either historical surveys or contemporary analysis.
Both species are currently common in other areas, so while it is possible that these species may still be living undiscovered in the Gilberts, it is more likely that the local populations have been driven to extinction.
“When we looked we found this shadow biodiversity, hints and whispers of what these reefs used to be like. It’s our hope that by understanding how reefs used to look we’ll be able to come up with conservation strategies to return them to their former vivid splendor,” said Dr Joshua Drew from Columbia University, first author of the study published in the open access journal PLoS ONE.
“Sharks in these waters play important ecological and cultural roles, and understanding the historical ecological conditions of these reefs is an important first step in evaluating conservation efforts.”
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Bibliographic information: Drew J et al. 2013. Shark Tooth Weapons from the 19th Century Reflect Shifting Baselines in Central Pacific Predator Assemblies. PLoS ONE 8 (4): e59855; doi: 10.1371/journal.pone.0059855
