Crown of Thorns starfish kills coral life

The Sri Lankan Navy recently collected 46 Crown-of-Thorns starfish in the Pigeon Island Park, in Trincomalee. This was during a cleaning program that was organized together with the Marine Environment Protection Authority (MEPA), to commemorate World Ocean Day. The Crown-of-Thorns starfish are usually found on coral reefs in the Indo-Pacific region and is found to destroy corals.

Wait, a coral-killing starfish?

Known by their scientific name, Acanthaster planci, the Crown-of-Thorns is a large starfish that feasts on corals. These starfish usually grow up to 25 cm (13.8 in) and can have up to 21 arms. The name Crown of Thorns come from the venomous spikes around its surface. But despite the sharp spikes, its body surface is soft and membranous in general.

This particular starfish primarily prey on hard, coral polyps. They tend to show preference to branching corals or table-like corals. In areas where less hard corals are found, the Crown of Thorns starfish feast on soft corals as well.

Removing the starfish from the corals is no walk in the park either. Usually, this requires injecting the starfish with Sodium bi-Sulphate via syringes with long needles. But sometimes they hide deep inside the corals and makes it extremely difficult to kill them off.

A coral reef menace

In countries like Australia and Sri Lanka, which are rich in coral reefs, these starfish are a real menace. Australia’s Great Barrier Reef has been a constant victim of these sea creatures. Just a few months back, a group of divers even made the effort to kill off a record-breaking 47,000 Crown of Thorns. According to the Australian Institute of Marine Science, coral cover between 1985 and 2012 declined by about 50%. The Crown of Thorns starfish are responsible for almost half of this decline.

Crown of Thorns Starfish | Coral Killer
Protecting the corals have been an uphill battle for many communities thanks to the menace (Image Credits:

In Sri Lanka, however, the situation is not as severe as you would see in countries like Australia. But back in 2012, Crown of Thorns numbers in the Pigeon Island exceeded the threshold of their natural occurrence. Efforts have been carried out ever since to keep this under control.

The need for coral monitoring

Clean up programs like what the Sri Lankan Navy did in line with National Environment Week, can do a lot of good. But protecting the corals and our oceans require a stronger push. Particularly because corals are on the endangered list of species. Crown of Thorns starfish outbreaks only makes this situation worse.

Crown of Thorns Starfish | Coral Killer
Hunting down the Crown of Thorns starfish menace

Current efforts in terms of coral monitoring and other marine-related research are carried out by organizations such as the National Aquatic Resources Research and Development Agency (NARA).


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