Controlling crown-of-thorns starfish populations

Natural controls

Crown-of-thorns starfish
Photo: AIMS

Natural controls on starfish populations include high mortality of the larvae, predation of small starfish and diseases. Adult starfish have few predators because of their tough and toxic ‘skin’ and long spines. There is little evidence of any major diseases in crown-of-thorns starfish.

Other control methods

Considerable effort has gone into developing methods to control large numbers of crown-of-thorns starfish in small areas by the Great Barrier Reef Marine Park Authority (GBRMPA), CRC Reef researchers and the marine tourism industry.

It is impossible to eradicate crown-of-thorns starfish from reefs where they are in outbreak densities. However, with sufficient effort, small areas can be protected. Because starfish can quickly move from one area to another, control of a specific area must be an ongoing effort and may be required on a daily basis.

The recommended control method involves trained divers injecting sodium bisulfate (dry acid) solution into the starfish, which kills them within a few days. This chemical is non-toxic to other marine life.

This control method is extremely costly. Some tourism operators in the Cairns region spend up to $300,000 each per year in crown-of-thorns starfish control. During active outbreaks, operations may need to inject 200 to 500 starfish every day in an effort to keep selected sites free of starfish. In 2001, the Commonwealth and Queensland Governments committed $2 million to a two-year, industry-run crown-of-thorns starfish control program that services the Cairns, Townsville and Whitsunday areas. This program is supported by the Great Barrier Reef Research Foundation.

Future research

Scientists will continue to search for the cause or causes of crown-of-thorns starfish outbreaks. They will also:

Continue to monitor crown-of-thorns populations.
Investigate links between terrestrial run-off and crown-of-thorns starfish outbreaks.
Investigate more cost-effective methods to control crown-of-thorns starfish.

Crown-of-thorns starfish | History of crown-of-thorns starfish outbreaks | What causes crown-of-thorns starfish outbreaks? | Recovery of reefs from crown-of-thorns starfish outbreaks | Managing crown-of-thorns starfish outbreaks | Development of cost effective control strategies for crown-of-thorns starfish | CRC Reef research projects on crown-of-thorns starfish