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Citizen Science for Crown of Thorns Control

Crown of Thorns are a natural part of coral ecosystems at low densities, but population outbreaks can lead to significant damage and declines in coral cover. 


About Crown of Thorns Starfish

Crown of Thorns Starfish (COTs) are naturally occurring corallivores, this means they survive by feeding on coral polyps. These starfish are covered in long, venomous spines and can range in colour from purplish blue to reddish-grey to green. They typically have a diameter of 25-35 cm, with a maximum width of 80 cm.

COTs prey on various types of corals, consuming approximately 10 square meters of reef per year. They have a preference for branching and table corals, such as Acropora species, which are known for their fast growth.

By consuming these fast-growing corals, COTs play an important ecological role in creating opportunities for slower-growing corals to populate available substrate.

Outbreaks destroy reefs! We need you!


Natural Role in the Ecosystem and Invasive Potential

While Crown of Thorns Starfish can have beneficial impacts on coral reefs at lower densities, outbreaks of these starfish can lead to significant damage and declines in coral cover. During outbreaks, COTs can consume coral faster than it can regrow, resulting in the depletion of living coral tissue by up to 90%.

Outbreaks can be attributed to two primary factors:

Firstly, the loss of natural predators, such as the giant triton snail, titan triggerfish, starry pufferfish, humphead wrasse, yellow margin triggerfish, harlequin shrimp, and lined worm.

Secondly, poor water quality caused by pollution and sedimentation can lead to an increase in nutrients that promotes phytoplankton blooms, which, in turn, favours COTs larval growth.


Control and Removal of Crown of Thorns

Community involvement is crucial in monitoring and controlling COTs outbreaks. In certain areas, such as Puerto Galera, fishers and local organisations have taken an active role in collecting and monitoring COTs. The collective effort of these groups, has been instrumental in addressing outbreaks and protecting the coral reefs. 

Monitoring and reporting COTs sightings can play a vital role in managing outbreaks and helping us to help coral reefs.

If you come across an outbreak of Crown of Thorns Starfish during your dives or snorkelling trips, it is essential to report the sightings.

Venomous Spines and Proper Removal

COTs are equipped with venomous spines that can cause severe pain and harm not only to humans but also to other marine creatures.

Contact with these spines can lead to various symptoms such as wounds, swelling, paralysis, liver damage, and more. Immediate medical attention is essential if stung by a Crown of Thorns Starfish.

It is crucial to note that the removal of these starfish should only be attempted by experienced individuals with the necessary skills and equipment.


How to know if its an outbreak?

During outbreaks, COTs are more likely to be active during the day, even though they are typically nocturnal.

If you observe multiple COTs during a dive or in a specific area, it could indicate an outbreak situation.

As a general guideline, if you encounter more than two COTs within a 20-minute period, there is a high likelihood of an outbreak and it should be reported.


How you can help

By promptly reporting COT sightings, you contribute to the collective effort in monitoring and controlling outbreaks, helping protect the health and diversity of coral ecosystems.

1. Report Crown of Thorns Outbreaks

If you come across COTs outbreaks (more than two COTs within a 20-minute period) during your diving or snorkelling adventures, reporting their sightings is crucial.

Please provide the following information: the location, time, depth. While photographs are not essential they can be useful so please upload any you may taken.

2. Spread the word about Crown of Thorns

Spread the word among fellow travellers and encourage their participation in data collection efforts. Together, we can expand the reach of our partnership and make a significant impact on the control of Crown of Thorns Starfish and the health of our precious coral reefs.

3. Expand Your Knowledge of Marine Ecosystems

Deepen your understanding of marine ecosystems, their inhabitants, behaviors, and their habitats.

The more informed you are, the more meaningful your contributions will be towards the conservation and protection of these remarkable marine ecosystems. 

By actively reporting Crown of Thorns outbreaks, we can make a significant difference in the conservation of coral reefs. Your citizen science contributions play a crucial role in the global effort to protect these magnificent ecosystems. Join us in this exciting journey of discovery and conservation.


Report an outbreak

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