Thresher Shark Divers‘ Instructor team, aka ‘The COT Squad,’ have been working hard to help in the process of eradicating the Crown of Thorns Starfish that are feeding on the coral reefs of Malapascua’s dive sites.
The adult Crown of Thorns is a carnivorous predator that can consume up to 6 square meters of living coral reef per year. It preys on coral polyps absorbing nutrients from the coral tissue leaving a white scar of the coral skeleton which quickly becomes infested with algae.
Researchers are not entirely sure why the outbreaks happen but do have some hypotheses. One possible cause is predator removal due to overfishing and habitat destruction. Another being that simply a dense population looks like an outbreak because they have consumed all of the nearby coral. Others theorize that increased terrestrial runoff causes increased nutrients for better larval survival.
We do know that females can produce up to 20 million eggs per year and even if only a very small portion survive, that is still a substantial amount of new Crown of Thorns every spawn.
We wanted to make a difference and help control the outbreak around Malapascua.
In 2005 and again at the start of 2012, TSD spearheaded a program to pay local fishermen to remove the creatures from the waters around Malapascua. We rallied local businesses as well as customers to donate. It as a great success: we removed 40,000 creatures in 2005, and over 200,000 in early 2012! You can read more about this program here.
Crown of thorns after removal from the water
This was great news for Malapascua and reduced the numbers considerably. However, this method was only good for our shallower sites around Malapascua Island itself, and did not work for our deeper sites like Monad Shoal, home to the famous thresher sharks.
In August, Thresher Shark Divers initiated what has been found to be the most efficient practice for controlling Crown of Thorns destruction to our coral reefs – injecting sodium bi-sulphate into the starfish. Sodium bi-sulphate is deadly to the Crown of Thorns but does not harm the surrounding reef or ecosystem.
We imported specially made kits from Australia which contain a gun, a long needle so we can inject from a safe distance, and a “Ghostbusters” style backback to hold the solution. So not only can we get rid of the COTs, but we can look ultra-cool at the same time. Always an important consideration for us dive pros.
We have found that injecting into the central aboral plate seems to immobilize them and then it is necessary to also inject near the arms to stop the tube feet. Through observation, once injected, the starfish is dead and begins to disintegrate within 24 hours.
‘The COT Squad’ are out a few times a week trying to save our coral from these detrimental predators. So far this month, we have been able to cull around 800 Crown of Thorns on Monad Shoal, 50 at Laplight, and 80 at North Point. On Old Monad, the dive site from Shark Point to Manta Point is pretty much clear now. They seem to be moving South on the Shoal so the next step will be to try to get ahead of the advance and sweep them back.
The COT Squad is going out regularly and will continue to help protect our corals!