【Survey Details】

In the Chichijima archipelago, we periodically (once every one to two weeks) visit all of the approximately 30 beaches to survey the number of egg-laying nests and turtle landings on each beach. When we find the remains of an egg-laying nest, we poke around it with a “rebar” (an iron bar) and look at the texture of sand unique to nests. Once the nest’s location is confirmed, we check the condition of the eggs and cover them back up with sand. We then set up three sticks at the nest’s location, measure its position and record it. In the Archipelago islands of Hahajima and Mukojima, we conduct research camps two to three times during the nesting season to conduct similar surveys.

What kind of information did the Center staff find

The green turtles that lay eggs in the Chichijima Archipelago have the characteristic of dispersing and landing on beaches here and there. However, there are also many beaches where they only land and do not lay eggs, so the nesting beaches are uneven. Green turtles prefer beaches with good sand quality and depth. The graph below shows the number of egg-laying nests over the years. The number of nests has increased and decreased repeatedly but overall an increasing trend is observed: about 450 nests in 2001, about 1,200 nests in 2005, and 1,949 nests in 2013, the highest number since the Marine Center began conducting surveys.