Factors affecting the long-term population dynamics of green turtles (Chelonia mydas) in Ogasawara, Japan: influence of natural and artificial production of hatchlings and harvest pressure

Published source details Kondo S., Morimoto Y., Sato T. & Suganuma H. (2017) Factors affecting the long-term population dynamics of green turtles (Chelonia mydas) in Ogasawara, Japan: influence of natural and artificial production of hatchlings and harvest pressure. Chelonian Conservation and Biology, 16, 83-92.
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This study is summarised as evidence for the following.

	Action	Category
	Regulate wildlife harvesting Action Link

Regulate wildlife harvesting

A before-and-after study in 1975–2015 in two island groups in Ogasawara, Japan (Kondo et al. 2017) found that in the years following regulations to limit the annual harvest of green turtles Chelonia mydas and a long-term programme of allowing harvested females to lay eggs before being killed the estimated number of nesting female turtles and hatchlings tended to be higher. Results were not statistically tested, and the effects of the interventions cannot be separated. The estimated number of nesting female turtles tended to be higher following regulations (180–580 turtles/year) compared to before regulation (25–210 turtles/year) and in years that regulation started (110–205 turtles/year). The number of hatchlings produced in natural nests was also higher in years after regulations were put in place (10,000–95,000 hatchlings/year) than before (0–16,000 hatchling/year). Fisheries regulations implemented in 1994 and 1997 limited the annual catch to 150 and then 135 turtles/year respectively. In 1975–2008, harvested female turtles were taken to an enclosed beach to lay multiple clutches of eggs before being killed. Surveys were conducted in May–September 1975–2015 (Chichi-jima islands) and 1988–2015 (Haha-jim islands) and used the number of nests to estimate abundance of females (see paper for details). In July–November, nests were excavated, and hatchling numbers were estimated by counting empty shells.

(Summarised by: William Morgan)