Important Coral Reef Areas in Okinawa Prefecture are selected areas that Okinawa Prefectural Government should protect from the Crown-of-thorns Starfish (COTS) outbreak areas selected in 2006. The selection criteria for the Important Areas are: "high coral cover," "an area capable of continuing conservation activities," "the local people wishes to protect the place". As a result of a series of the Spot-Check Survey and an interview survey, a total of 50 coral reefs were selected.
"Coral Reefs in Okinawa - Important Coral Reef Area in Okinawa Prefecture" was created by the Coral Reef Conservation Project.

Crown-of-thorns Starfish (COTS)
The Crown-of-Thorns Starfish (COTS), Acanthaster planci, is a large, multiple armed starfish with hundreds of sharp poisonous spines covering the upper surface of its body. The Crown-of-Thorns Starfish receives its name from thorn-like spines. Because COTS usually preys upon hard coral polyps (Scleractinia), outbreaks of COTS causes extensive damage to coral communities.

Watershed and Reef Unit (WRU) is a unit of land and its neighboring sea, which sets the boundary from the viewpoint of water flow. Rainfall on land flows into the sea through a river. The river runoff influences the environment in the sea. Such a sea area affected by the river runoff from a single watershed is called Reef Unit. We set a boundary of each Reef Unit according to the topography of the sea floor.

Watershed (Drainage Basin)
Watershed is an area of land where surface water flow to lower elevation and gather to a single point. Drainage basin was obtained by the topography (altitude) and/or groundwater flow data.

Reef Unit (Nakai 2009)
Ecological unit semi-closed by cape, channel and reef flat.