Crown of thorns starfish (COTS)
The Crown of Thorns Starﬁsh (Acanthaster planci) or COTS, commonly feed on corals throughout the Indo-Paciﬁc region. When in low numbers these starﬁsh are important for the general health of the reef, as they feed on faster growing corals (e.g. stag horns and plate corals), which indirectly help the growth of slower growing corals. This supports coral diversity within a reef ecosystem making it more resilient to other pressures such as cyclones, coral bleaching and climate change. In this situation, COTS control is not necessary, as the coral reef can and will recover from the relatively limited damage. However, when the number of COTS increase to the point where the coral reef can no longer recover from the damage caused, it creates a cause for concern. This is what is known as an outbreak.
The classiﬁcation of what is considered an outbreak is variable, but it is generally when more than 1 COTS is seen during a 20 minute swim.
Why are they a problem?
These starfish have the potential to release millions of eggs during their spawning season from November to February. Their population is usually kept in check by a balanced and biodiverse coral reef. Unfortunately, due to human activities this 'balance' has been altered, increasing the chances of survival for the COTS. The two main contributors causing the increased occurrences of outbreaks include;
No permit is required to remove Crown of Thorns Starfish from Vanuatu, but their collection involves some level of risk.
The Great Barrier Reef Marine Park Authority has developed a number of resources to carry out the removal of Crown of Thorns safely using injection guns with bile salts or sodium bisulphate (please see resources below). Acetic acid (White Vinegar), is also an effective alternative.
In Vanuatu, there are many remote and isolated locations with limited resources and accessibility, thus local communities readily control outbreaks through manual removal. This method involves a high level of risk and is labor intensive and significant caution should be taken if this method is used. A number of communities in Vanuatu have also used the starfish carcasses as a compost and converted it into a commercial fertilizer.
report sightings of crown of thorns
The Vanuatu Department of Fisheries have an online reporting system for sightings of this invasive species. This information will assist us to identify areas of a potential outbreaks and implement management strategies to safeguard our reefs. This will required the following information;
Jayven Ham (Fisheries Officer)
Vanuatu Department of Fisheries www.fisheries.gov.vu
(+678) 23119 | (+678) 5333340
During peak season (April - October), yachts can Tune into the Vanuatu Radio Net each morning at 7.30am (USB frequency 8230) for updates, sightings and reports.
avoid catching these species
One of the key causes thought to be contributing to the greater frequency and density of COTS outbreak, is linked to the removal of their predators. There are a number of marine animals that feed on adult COTS. Therefore we discourage their purchase or capture. These include;
(Click on the images above to download the pdf files)