Thorn in our Side….

Well actually the thorns mostly hit our fingers and for many of us the memories of the week stay in the tingling tips of our fingers.

What were we up to? Removing those nasty, spine heavy starfish called Crown of Thorns (COTS), (Acanthaster planci) or locally known as ‘Alamea.

Did you know that COTS can have up to 21 arms and reach diameters of over 80cm! The spines are long and carry a toxin in them that will make your fingers swell up and be extremely painful. Though the toxin is not life threatening, several stings can be quite traumatic and care needs to be taken.

COTS starfish are a native but voracious predator to coral reefs in the Pacific region and for a starfish are able to move fast covering 20 meters per hour (Ref), they eat the fleshy polyp of the coral leaving a trail of white destruction.

The white coral skeleton left behind as the predatory COTS moves on to the healthy side. Photo credit: © Karyn Von Engelbrechten

As COTS are native to coral reefs, small occurrences can be beneficial (estimates of 6-20 per km2), however when occurrences are observed over this and destruction of corals is extremely visible, management practices need to happen. The COTS natural predators include the Triton Trumpet (Charonia tritonis), Kele’a and some fish species including Napoleaon Wrasse (Cheilinus undulatus), puffer fish (Arothron hispidus) and triggerfish (Balistoides viridescens) (Ref) however these  predator species are often in low abundance and slow moving to be able to deal with COTS on a frequent basis.


The SCUBA team from Department of Environment, Penikoni ‘Aleamotua, Senituli Finau and Brian Fusimalohi. Photo credit © Karyn Von Engelbrechten



Population outbreaks are strongly linked to nutrients enrichment primarily from heavy rain fall and subsequent run off and it appears from surveys conducted we have “hotspots” located near channels and high current areas. When COTS spawn, they release eggs which are fertilised and develop into larvae which are carried currents, these larvae settle on other coral reefs, allowing for other reef sites to be affected.




SCUBA diver from VEPA removes COTS using barbecue tongs and places them in a flour sack to be brought back to land. Photo credit: © Karyn Von Engelbrechten

Currently, our only way to manage COTS is with active hands on removal, though worldwide new techniques have emerged for injecting them with vinegar, we currently don’t have the equipment to manage them this way. Manual management programs are costly and to be able to maintain and monitor COTS populations, we need to be out there as often as possible whilst at the same time looking for way to gain the equipment that would ease the management process.

In order to make sure manual management is successful, the following is critical:

  • COTS must not be broken up when removing, each arm can become a new COTS if broken
  • Care is taken not to damage other corals around when removing the COTS
  • COTS must be removed completely from the ocean
  • Use long tongs to keep hands a safe distance away from the spines
  • Wear heavy builder gloves (not always available here) to protect from spikes but be mindful not to grab on to live corals around (its why we are gloveless!)
  • If your fingers meet a spine and gets pricked, make the affected area bleed through the pricked area as much as possible and for as long as possible immediately following the incident

It is extremely important that COTS are removed effectively and that management practices are adhered to, otherwise “help” can create an even bigger “storm in the teacup”.

Over the course of the 3 day management programme we removed 638 individuals from primarily 3 reef areas. Still today, we are getting reports from kind visitors about other areas they are seeing. We hope to be out there again soon and developing ways that communities and tourism operators can assist.

Data is collected on the minimum and maximum diameter of the COTS by the SCUBA and snorkel teams. Photo credit: © Karyn Von Engelbrechten
Penikoni ‘Aleamotua from Department of Environment, uses a pry tool to remove the COTS without damaging it. Photo credit © Karyn Von Engelbrechten











The oceans and coral reefs face many threats from over exploitation (fishing), climate change and pollution (land and marine based) and COTS outbreaks are high on the list too.

The COTS marine team consisted of trained SCUBA divers from the Department of Environment (MEIDECC), Ministry of Fisheries and the VEPA team. These partnerships are invaluable to the future of our corals and coastal management.

This program was funded jointly by the “Strengthening Protected Area Management (SPAM)” through the Department of Environment and VEPA (through grateful donations!) and the vessel was provided by the Ministry of Fisheries. Big thanks as well to Karyn Von Engelbrechten for the photos that help us to tell the story.

Further Reading:

One response to “Thorn in our Side….”

  1. A very well presented story on a very important reef management effort that not only removes/lessens the COT threat to the coral reefs, but also involves many advocates of coral reefs to spread the “word” about this semi-natural problem. The mentioning of land-side education on reducing nutrient-loaded runoff is also important and can be effective by involving the non-diving citizens who value the coral reef resources. VEPA – let me know the style/kind of heavy rubber gloves that are the most useful for removing COT and I will be pleased to make a donation on my next trip to Vavau. Good work all.


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