They can grow up to 19 legs, have highly venomous spines, and leave a path of dead coral in their wake.
What am I talking about?
Crown of Thorns
For a healthy reef system, crown of thorns would be just another part of a balanced ecosystem.
They would eat the faster growing corals that would normally take over inhibiting the slower growing more hearty corals from thriving.
Crown of thorns would also open up coral skeletons leaving a clean ground for juvenile corals to settle in.
Now that humans have tampered with the balance of our oceans crown of thorns have taken over fragile reef systems.
Rising temperatures in the oceans are happening so rapidly that reef systems cannot properly adjust causing the corals to become highly stressed.
When the corals are stressed they emit a chemical that crown of thorns can sense.
This stress also weakens the corals defenses against crown of thorns and other predators.
Now it is up to humans to try and fix the problem that we created.
From what I’ve read, a healthy number of crown of thorns is about 2-3 per dive, but here it seems like we see at least a half dozen almost every time we go out.
This is why we have to do a crown of thorns collection every so often to try and control the population.
There are a few different ways to extract them, but it can be very tricky. Their spines are highly venomous, and I’ve heard getting stuck by one feels like a hammer being pounded against your skin.
One way to get rid of them is to simply gather them up and set them on the beach to dry out.
When I helped with the extraction, we used tongs to pull the crown of thorns out from the coral, and then placed them in a rice sack. We then set them to dry on the beach.
Personally I don’t 100% care for this method.
I understand they are killing the coral, but it’s because of what humans have done that we are even having this problem!
Another way to get rid of them is by flipping them over and placing a rock on top of them.
Naturally larger fish like the Titan Triggerfish would use it’s beak to flip the crown of thorns over and eat it’s underside, but over fishing has caused the numbers of these predatory fish to dwindle leaving the door wide open for crown of thorns to multiply.
By flipping the crown of thorns and placing a rock on them, it exposes their fragile underside so all fish can eat them without risking being stung by their poisonous spines.
Lately we have been using this method when we see crown of thorns while we are diving.
Then they are at least going back into the ecosystem and not just rotting on the beach.
There is a long way to go before the crown of thorns issue is under control, but hopefully we will one day get our reef system back into a good balance so we won’t have to extract them anymore.