Red, pink and white corals inhabit 100-300 m deep waters in and south of Sagami Bay around Japan. They are harvested in Kochi, Kagoshima and Okinawa Prefectures. The distribution density of them has been investigated since 2009 at 20 sites off Kochi, Kagoshima and Okinawa using remotely operated vehicles (ROVs). According to the research, the average distribution density of three precious coral species is 0.74 colonies/100 m² while that of red coral, the most commercially valuable species, is 0.45 colonies/100 m².
　Precious corals in a protected and a non-protected area in Tosa Bay, Kochi Prefecture, have also been surveyed. Corals in the protected area are larger in size and higher in distribution density than corals in the non-protected area. The study has confirmed that setting up areas where coral fishing is prohibited is beneficial to the protection of precious coral resources.  (Nozomu Iwasaki of Rissho University)

[Reference]
●Iwasaki. N., Fujita. T., Bavestrello. G. and Cattaneo-Vietti. R., 2012.
Morphometry and population structure of non-harvested and harvested populations of the Japanese red coral (Paracorallium japonicum) off Amami Island. southern Japan. Marine and Freshwater Research, 51 (3). 372-382.