[Coral-List] sea urchin removal to prevent bioerosion

Clement Dumont cdumont at hku.hk
Wed Feb 17 03:01:10 EST 2010

Dear all,
thank you for all the comprehensive replies from which I learned a lot. My initial question, however, remained unanswered. Does anybody is aware of report/publication of such removal practice of grazers to protect/restore coral reefs (i.e. removal program similar to the crown-of thorns)?
 I have also a project in Malaysia where the Marine Park rangers remove every year the sea star Acanthaster planci in an attempt to prevent population outbreaks. However, when I found similar densities of sea stars at the sites where removal occur with sites where no sea stars are collected. Unthinking removal programs are generally unsuccessful and can even further damage the corals (e.g. Japan sea star removal).

Best wishes,

Date: Thu, 11 Feb 2010 08:54:02 +0800
From: Clement Dumont <cdumont at hku.hk>
Subject: [Coral-List] sea urchin removal to prevent bioerosion
To: "coral-list at coral.aoml.noaa.gov" <coral-list at coral.aoml.noaa.gov>
        <A079DF1679D36540A0B97A14317E122A12B13FA575 at MAIL.hkucc-com.hku.hk>
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Dear all,
the Hong Kong government took the initiative (based on brief observations) to remove every year thousands of the sea urchin Diadema setosum and the corallivore snail Drupella sp. to prevent the excessive bioerosion of corals (but no studies have been conducted). Being really surprised by this initiative, I started a cage experiment with different densities of urchin to examine whether Diadema is the major factor contributing to bioerosion. With no much surprise (the experiment is still running), we have a higher recruitment of macroalgae and also higher sedimentation on corals non-exposed to sea urchin grazing and even with high densities densities of urchins, still no sign of bioerosion. Hong Kong waters are highly polluted and the nutrient enrichment and high sedimentation may rather be the main causes of corals degradation.
I am therefore curious whether such sea urchin removal practice (not on a fishery purpose) is/has been conducted elsewhere to prevent bioerosion of corals.


Clement Dumont
Research Assistant Professor
The Swire Institute of Marine Science
& The Division of Ecology & Biodiversity
The School of Biological Sciences
The University of Hong Kong
Pokfulam, Hong Kong, PR China

Phone: (852) 51 99 1730
Webpage: http://web.hku.hk/~cdumont/

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