RADIOCARBON DATING OF PRECIOUS CORALS OFF THE SOUTHWEST COAST OF KOCHI PREFECTURE, SOUTHWEST JAPAN

Radiocarbon (C-14) dating was performed for various types of precious coral colony fragments collected from the Ashizuri fishing field, around 100-200 m deep, off the southwest coast of Kochi Prefecture, Japan, to understand the historical background of one of the largest precious coral fishing fields in Japan. The 14C ages of the 55 specimens range from similar to 7500 years ago to the modern. Most of the measured samples were older than 1871, when fishing activities of precious corals began in Kochi Prefecture. These results suggest that most of the deaths of the precious coral colonies were due to natural causes, such as natural mortality, predation, or various forms of environmental degradation, and not strictly related to destructive fishing practices. Additionally, precious corals started inhabiting the study area at least similar to 7500 years ago, when the marine condition became similar to that of today after the Last Glacial Period. This study is the first to focus on the age of dead precious coral fragments and has revealed that they might be an important fossil resource that could lengthen the timespan of precious coral fishery. This additional time may enable us to establish reasonable and effective regulations for sustainable fishery.