Coral reefs have degraded over time and, recently, severe bleaching events caused further damage to coral communities worldwide from 2015 to 2017. Because coral reefs are an important habitat for coastal fish and invertebrates in tropical coasts, the decline of coral reefs also results in decreased fishery productivity. Therefore, for sustainable use of these resources, it is important to conserve coral communities that act as fishing grounds and fish nurseries. Coral transplantation is known as an effective restoration method. However, large-scale transplantation requires a great deal of labor and the transplanted corals are vulnerable to extermination by only a single disturbance such as bleaching or an outbreak of crown-of-thorns starfish (COTS). Hence, enhanced annual coral larval recruitment is needed for sustainable large-scale restoration. Two key factors are crucial for sustainable coral restoration by enhancing reproduction. The first factor is establishment and maintenance of “artificial spawning hotspots” that consist of densely populated conspecific adult colonies. The second factor is improvement of early life survivability by collecting eggs and sperms at spawning and rearing larvae until settlement. For “artificial spawning hotspots,” safeguards are required against predation by COTS and the use of shading is desirable against bleaching during the high seawater temperature season. In addition, a special gamete and larval collector, termed “larval cradle”, was developed to consistently perform bundle collection, fertilization, and larval rearing. Eventually, it is suggested that a set of simple methods and techniques are used for sustainable large-scale coral restoration.
Go Suzuki (Mon,) studied this question.