How to control Crown of thorn star fish?

[searider]

I dove in other place (not to mention where it is) what took my attentioned is the large number of crown of thorn..How this thing being control?

Thanks..
Sea Rider

 

[Diver Dennis]

Hi searider. I think the only way to control them is to remove them from the ocean. As you know, they are very difficult to kill.

How's the weather there this week?

 

[Doc]

I dove in other place

This was photographed 300 meters East of Sabang beach.

It is all but impossible to eradicate a species... unless you were trying not to.

 

[prskate2]

Wow.. never seen one of those before. Nice.... but not to step on.

 

[RAWalker]

From what I've been reading about the problem it seems that the root cause of their population explosion has been traced to runoff that is high in nitogen content. It causes certain algae populations to expand giving a food source to the young Crown of thorn.
So bottom line has to be to stop the runoff from getting into the water.

 

[Hank49]

I've seen a population of them just after the Great El Nino of 1998 (that's what I call it, but it's not official) on Boracay, Philippines. Most of the coral had bleached and was weakened or dying. The cots came in afterward, by the thousands, and cleaned up what was left. There was speculation that healthy reefs have natural (enzymes excreted?) protection that keep them in check but since the reef was all but dead, they had not resistance. In support of the natural defence theory, the cots didn't spread all around the island. they were more or less isolated to the west side where there is little tidal current and this may have resulted in higher water temperature, contributing to the bleaching of the coral in that area. The north and south ends, which have strong tidal currents, didn't bleach and although the cots reached the borderlines of healthy coral, they seemed to stop there, or at least their damage was minimum.

 

[cruiser]

Also read that the Crown of Thorn's natural predator is the Triton's Trumpet (which has been overfished by collectors) leaving the starfish population to thrive.

 

[justleesa]

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[Hank49]

Also, we tried different methods, but to no avail, of eliminating them. We injected chlorine, but you have to inject every appendage at the base since all have a reproductive system there (12 in each animal)
We finally resorted to collecting them every Monday, with as many as 30 divers putting them in feed bags. When we'd go back the next week, you couldn't tell we'd ever been there. It seems they just ran their course.
When I returned there after 8 years (last June) the coral was making a comeback off the beach there.

maybe the runoff (nitrogen theory) weakens the coral and lowers its defences in the same manner that the high temperature did. ??

As you can see in RoatanMan's photo, the coral where the COT is feeding is more or less dead and it's most likely cleaning up those few remaining live ones. this is what we saw in 1998.

 

[fisheater]

Not that it's a solution to the overall problem, but I saw a DM bash a crown of thorns with a rock and then place a Triton's Trumpet on top. After we'd checked out other parts of the dive site and returned, the Trumpet had opened up and was business devouring the crown of thorns.