The Drupella Dredger

Drupella snail management on our island is set to make a major leap forward this year. On Wednesday, the 11th of February we will be launching a Crowdfunder page in order to raise the money we need to construct a ‘Drupella dredger’, a large underwater vacuum to suck the little predatory snails right up off the corals. Based on our project plans, we expect the device to cost about 1,800 GBP to construct, but once it is built it can easily be transported to any local reef needing it, and should last for years.

At the moment, we need your help to spread the word and assist us in raising the money to build it. You can pledge any amount, from 2 GBP to 200 GBP, which will greatly help us on our way to achieving our goal. You can also help by spreading the word, and sharing the news about this vital project.

Drupella snails are a small marine snail, about 2-4 cm in length, which feed on the tissue of hard corals.  Each one consumes only about 1.8 square centimeters of coral in a day, but in outbreak situations they can quickly devour all of the slow growing corals from the reef. The first outbreak of Drupella was recorded in 1982 in Japan, and since then there have been recorded outbreaks in areas as far as Hong Kong, Kenya, the Red Sea, Australia, and Thailand. The cause of Drupella outbreaks is usually increased larvae survival due to increased nutrients in the sea from human activities, and less fish around to eat the juveniles due to over-fishing. For coral reefs degraded by human activities, Drupella snails and other coral predators can be the proverbial ‘straw that broke the camel’s back.’ And once the coral reef ecosystem is gone there is little to no hope of it coming back again.

Drupella snails eating a rare species of Table coral on Koh Tao (Acropora millepora).

On our reefs, sometimes more than 200 snails can be found on a single coral, which they consume within days before moving to the next coral colony. Since 2010, our program has been monitoring and documenting the situation, and also spending hundreds of diver hours to collect the snails from the reef. Already we have collected about 30,000 of the snails, which sounds like a lot, but is really just a start (see our info-graphic about Drupella Snails collections). That number has taken us about 5 years to achieve, and has involved hundreds of divers picking up each snail one by one from the corals, which is not easy work. The snails are not usually on the top of the corals, but are instead tucked deep into the complex structure, out of reach for human hands. To make matters even more frustrating, when they are in clusters and a diver reaches for them, many will immediately drop down into the complex reef structure below. We have tried various tools to assist reaching into the corals, but most are too difficult to use efficiently while scuba diving. In order to have real success in managing these populations before they get even bigger, we need better technology.

That is where our Drupella Dredger comes in. Based on gold dredging equipment, this device would allow us to use a 6 cm wide pipe to selectively vacuum the snails from the reef. This will allow a single team to collect thousands of the snails in a day, achieving removal rates that could not be realized when collecting by hand. The device will also mean that divers will not have to reach into corals, eliminating the risk of scrapped hands or accidental breakage of delicate coral branches. The underwater vacuum will be powered by a pump floating on a small raft, which will be towed above the diver, and will have a large basket to catch the snails. Once the dive is complete the basket can be sorted, and any non-Drupella snails inadvertently sucked up can be immediately released back to the reef.

Although removal of the snails will not solve the root of the problem, declining water quality and over-fishing, it will help us to locally address the symptoms and preserve our reef biodiversity and abundance, thus buying us some time to address these global issues. Coral reefs are one of the most productive and biodiverse ecosystems on the planet, but also the most threatened. Already, about 90% of the Caribbean reefs and more than 50% of the Great Barrier Reef has been lost, and all possible solutions are needed in order to stop global reef decline before it is too late.

In addition to all of our other education, research, restoration, and protection activities; the Drupella Dredger will help us to immediately address one of the more salient threats to local reef health while still working towards a larger and more holistic model of sustaining our natural resources. We invite your support in these efforts, and welcome any assistance you can provide us in reaching our fundraising goal.

Thanks to everyone who backed The Drupella Dredger, we didn't make it this time.


If you would like to donate, you can click onto our Crowdfunder page and find out more about the options and rewards. We also invite you to follow along with this exciting project on our facebook page and website. Thank you for your support!

E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.
Phone: +66 (0)77 457045 or + 66 (0)91 8324800
48 Moo 3 Chalok Baan Kao
Koh Tao, Surat Thani
84360 Thailand

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