This beautiful multiarmed starfish is called Crown of Thorns and it was picked up and destroyed only seconds after the picture was taken. The local divers fear them. Not because they are slightly poisonous and cause pain and swelling if stung, they fear them because they sometimes multiply in great numbers and destroy the reefs for decades. These plagues or outbreaks were first made famous at Great Barrier Reef in the early 60s where they baited down large portions of the reefs off Cairns. They eat the hard corals and miles of reefs were turned into a moonlike landscape. Scientists studied these outbreaks for years and saw them pop up from the Red Sea through the tropical Indo-Pacific region and all the way to French Polynesia.
Between 1965-1980 over 20 outbreaks was recorded. The scientist did not land on a single cause of this phenomenon but the “predator removal hypothesis” was one of the most likely answers. Even though some puffer fish and triggerfishes are known to prey on the Crown of Thorns the main enemy is the Triton large mollusk. The hypothesis concluded that in areas where this Triton was over collected the outbreaks were more likely. Man made over collecting of one shell, disturbing the environment. This picture was taken at Rarotonga where they had one outbreak 15 years ago. The scars on the reefs are still highly visible and the divers do whatever they can to keep it from happening again – and at the same time you see the fishermen selling Triton shells at the market.