Press Release

November 1, 2012

Incorporated Administrative Agency, Fisheries Research Agency

Development of a propagation technique for artificially-produced larvae of reef-building coral with high survival rate
[10-fold improved survival over conventional methods for the first time in the world]

  • A high coral survival rate was achieved by artificially attaching coral larvae to grid-shaped reef beds.
  • Coral colonies can be repaired and established easily by using this technique.

In recent years, coral reefs in Okinawa and other parts of the world have suffered from bleaching due to loss of symbiotic algae and deterioration of the colonies by outbreaks of coral-killing crown-of-thorns starfish, consequently causing reductions in fish species that inhabit coral reefs. To restore fishery resources in coral reef areas, colonies of staghorn and elkhorn coral need to be recovered, such as Acropora spp, which serve as nurseries for fish fries. However, rapid restoration cannot be expected under natural conditions because only small number of coral larvae is supplied, and even fewer can survive. Artificial settlement of coral larvae has been studied in and outside Japan, but the survival rate was as low as ~1% at 6 months post settlement in natural environments.

The Fisheries Research Agency developed measures to increase the survival rate of coral larvae, by controlling the settling density of the larvae, using two layers of grid-shaped coral beds, and reducing the grid size of the beds. In these ways, larvae of Acropora spp were artificially produced and directly attached to plastic reef beds in the sea; then, a obviously high survival rate as high as 18.1% on average (maximum survival rate of 46%) was realized. This was the first breakthrough in the world; the colony density was as high as 10 colonies per 100 cm2 at 15 months post settlement.

By using this technique, it is expected that corals grow easily and effectively even in areas where there are few rocks that are essential for coral settlement (ex. on sandy or conglomerate covered sea beds). Thus, the technique should be highly effective for restoring and protecting coral reefs from local damage.

The study was funded by the project of the Fishery Agency entitled “Development and verification of coral propagation technique under severe conditions” and a joint study project between the Fisheries Research Agency and Daikure Co., Ltd. entitled “Development of coral beds easy to settle and survive.”

Young coral of Acropora spp. grown for 15 months on the grid-shaped bed
(Grid size: 4×4 cm)