Your input will help to manage COTs

in Raja Ampat Marine Park

The crown-of-thorns starfish (Acanthaster planci) is a species native to coral reefs in the Indo-Pacific region. One of the largest starfish in the world, it grows rapidly up to 60cm in diameter, and derives its name from its venomous thorn-like spines covering its upper surface.

Crown of Thorns Starfish (COTs) are widely distributed across the Indo Pacific, perhaps most common in Australia along the Great Barrier Reef, but occurring in the tropical and subtropical regions stretching from the Red Sea and East African coast, across the Indian and Pacific oceans, all the way to the west coast of Central America. COTs feed on hard corals, by releasing the contents of their stomach onto the coral, and using digestive juices to dissolve the coral for consumption, leaving behind only the white skeleton. With few natural predators (including triton trumpet, pufferfish, porcupine fish and napoleon wrasse), a mature COTs can eat up to 1m2 per day.

On healthy coral reefs, where populations exist in balanced numbers, COTs play an important role in reef health; by predating on the fastest growing corals, they enable the slower growing coral species to form colonies, thus contributing to coral diversity.

Yet in circumstances where COTs densities increase to a point where the coral reef cannot recover fast enough from the predation, this is considered an “outbreak” and poses significant threat to the health and resilience of a coral reef ecosystem.  In extreme cases of outbreak, such as the Great Barrier Reef in Australia, large areas of reef have been affected: coral cover on surveyed reefs in the GBR declined 50% between 1985-2012, with COTs responsible for almost half of this decline (Australian Government, Great Barrier Reef Marine Park Authority)

COTs in the Dampier Strait, Raja Ampat

At this point in time, the majority of reefs accessed within Dampier Strait and surrounds, are healthy and abundant, with few COTs are visible and coral growth and recovery in balance with any COTs predation.

However, there are several “hotspots”, where it is now considered that the densities and damage caused by COTs have reached outbreak levels, and these are areas of concern. At these sites preliminary observations show that as opposed to other parts of the world, COTs in Raja Ampat do not exclusively focus on fast growing corals, but have a much wider diet, predating on any coral colony available on its path.

Yet in circumstances where COTs densities increase to a point where the coral reef cannot recover fast enough from the predation, this is considered an “outbreak” and poses significant threat to the health and resilience of a coral reef ecosystem. In extreme cases of outbreak, such as the Great Barrier Reef in Australia, large areas of reef have been affected: coral cover on surveyed reefs in the GBR declined 50% between 1985-2012, with COTs responsible for almost half of this decline (Australian Government, Great Barrier Reef Marine Park Authority)

COTs in the Dampier Strait, Raja Ampat

At this point in time, the majority of reefs accessed within Dampier Strait and surrounds, are healthy and abundant, with few COTs are visible and coral growth and recovery in balance with any COTs predation.

However, there are several “hotspots”, where it is now considered that the densities and damage caused by COTs have reached outbreak levels, and these are areas of concern. At these sites preliminary observations show that as opposed to other parts of the world, COTs in Raja Ampat do not exclusively focus on fast growing corals, but have a much wider diet, predating on any coral colony available on its path.

In a place like Raja Ampat, where both the tourism economy and the local livelihoods highly depends on the health of coral reefs, it is vital to do whatever we can to mitigate further coral loss in the region. Rather than wait for existing outbreaks to potentially spread, or until significant damage occurs, Raja Ampat SEA Centre will work closely with Marine Park Authorities, Conservation International, and other stakeholders and operators, to manage ongoing monitoring and mitigation of the COTs outbreaks in the Dampier Strait region.

 

Objectives & Status

Methods of Removal

The collaborative response will involve 2 methods of removal.

1) Manual injection of the COTs carried out by trained divers. After consultation with marine scientists from Australia’s Great Barrier Reef Marine Park authority, and reviews of existing research and literature relating to COTs outbreak mitigation, it has been established that a single injection of 20ml of household vinegar is highly effective in culling. With vinegar easily accessible and affordable, this is the preferred (and safest) method of COTs removal from a coral reef.

2) Manual removal of the COTs. This involves divers using equipment such as bamboo, wood, metal tongs etc, to manually remove COTs from the water. Whilst still effective, this is more labour intensive with less COTs being removed per hour then the injection method. This method also poses the risk of being stung by a poisonous spine, resulting in severe pain and swelling at the site of contact. Anyone removing COTs using this method should take appropriate precautions (gloves, equipment long enough to keep the COTs away from body).

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