Crown of Thorns

WWF-

An infestation of predator starfish is decimating large tracts of coral reef throughout the Philippines.


The spiny and toxic crown-of-thorns starfish are voracious predators that can wipe out large areas of coral; an individual can consume up to 6 square metres of living reef per year. Outbreaks of the species often occur when ocean temperatures and nutrient levels increase. Crown-of-thorns starfish have long spines and are capable of severe stings. Contact will almost surely inflict severe swelling, pain and nausea that can last for hours or days.

Unfortunately, some of the starfish’s major predators, such as humphead wrasse and giant triton, which usually keep the species in check have declined in recent years as a result of overfishing.

“We are experiencing a return of the starfish in greater numbers,” said WWF-Philippines CEO Lory Tan. “The situation facing our reefs is far from normal.”

The Philippines once boasted 25,000km2 of coral reef. However, a recent World Bank study shows that barely 1 per cent of this area remains pristine, and more than 50 per cent are reported to be in decline or unhealthy.

To combat the outbreak, WWF-Philippines is enlisting the help of beachgoers to reduce the number of starfish in an infested area. The most recent action netted hundreds from the world-class diving site of Apo Reef off the west coast of the island of Mindoro, about 100km south of the capital, Manila.

“In the long term, the best response to the situation is by putting a stop to overfishing and agricultural runoff, and to better manage sewage,” Tan adds. “It’s important to keep our oceans clean and our reefs well balanced.”

According to a WWF survey, outbreaks of crown-of-thorns starfish have been reported at Apo Reef and Puerto Galera in Mindoro, as well as at Mabini in Batangas, Roxas in Palawan, Bolinao in Lingayen Gulf, and Kiamba and Glan in Sarangani Bay. It is possible that many other coastal areas have been affected as well.

OK, someone who knows better than me, please help me understand this a little better.

I have seen Crown of Thorns in Micronesia, a very cool looking starfish, got a couple of good photos somewhere. Only saw them very occasionally, and clearly no major problem at the time, the reefs were in pristine condition.

I realise that they eat their way through the reef and can cause a lot of damage when in large numbers. However, what I am not familiar with is the reasons for these apparent "swarms" and whether its a problem or just a natural part of reef ecology. They've been reported on the Great Barrier Reef for years and seem to come and go periodically. Is this just part of the natural cycles of the reef or is it a problem caused by something we've done.

Fertilizer run off, global climate change, over fishing are just some of the factors that we know can impact the ecology of the reefs, I'm just not familiar with what the scientific brains have discovered as the causes for this particular issue, or whether it really is an "issue" at all.

Typically mass infestations occur and anecdotal evidence suggests overfishing of their primary predators.

In Yap I only saw a few, I see maybe 3 in a week of diving in Puerto Galera in the Philippines, and last month in 9 days of diving in Anilao, Philippines I only saw 1.

Thanks, that makes sense, most populations are governed by either predation or food, one way or another. Take away the predators, population grows until food supply becomes the limiting factor. I realise that's an over simplification, but you know what I mean.