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Crown of Thorns Starfish

Reef Resilience features programs that have been developed to control COTS. Methods for COTS control include taking starfish ashore and burying them, injecting them with compressed air, baking them in the sun, injecting them with toxic chemicals (e.g., formalin, ammonia, copper sulphate), and building underwater fences to control COTS movement. The recommended method on the Great Barrier Reef is to inject sodium bisulphate solution into the starfish which kills the starfish but does not harm the surrounding reef ecosystem. Mechanical methods for controlling COTS are expensive and labor intensive, thus may only be justified in small reefs that have high socioeconomic or biological significance, such as important spawning sites, tourist attractions, or areas with extremely high biodiversity.

The Australian Institute of Marine Science runs a major crown-of-thorns starfish monitoring program on the Great Barrier Reef. This long-term program has shown that outbreaks have begun in the north and migrated southward over about a 15-year period, with ocean currents transporting larvae between reefs. The surveys also show that healthy reefs generally recover between outbreaks, taking 10 to 20 years to do so. However, recovery takes longer on reefs that are affected by additional stresses, such as coral bleaching, cyclones or poor water quality, so the coral may not fully recover before the next wave of outbreaks occurs.