[Coral-List] Rare "elkhorn-iike" Acropora on Arno

Dean Jacobson atolldino at yahoo.com
Sun Mar 18 06:41:11 EDT 2012


Sadly, I must report the demise of the "Pacific elkhorn" colonies on Arno atoll that I first located in 2004 and Zoe Richards later publicized in 2010, they have almost all eaten by a devastating Acanthaster outbreak.  This outbreak (first noticed two or three years ago) follows the huge Majuro outbreak that began in 2003 (I have done some small-scale control on Arno, removing around 100 animals).  I didn't realize the most high-profile coral species would be at the top of the menu.  My images are in a photo set:


I used Maria Beger's image as a "before" shot of the most visually striking of the colonies.

This most spectacular colony, with the parallel "V" branching pattern, displayed the very last of feeding activity, with several fresh feeding scars at the tips of branches... but the last one or two cm of a few of the branches were still alive last week, and I hope the COTS don't go to the trouble to crawl out for the remaining fragments of tissue (they clearly find this species irresistible and no doubt locate it by chemosensory cues, they are not even touching the A. cytherea they usually feed on).  I am organizing a COTS control dive (night dives) and I expect we will be able to collect over five hundred animals without difficulty, if I can round up enough divers.  I intend to follow up with monthly collection dives.  I know this is a fool's errand, but this is a particularly charming reef (luckily the two giant Leptoria colonies, almost 3 meters across and 2 meters tall, were untouched) and control efforts will be focused on a 100 meter area.

I have a question: can anyone suggest a way to cultivate the branch tips, in case any survive?  I know suspended line culture can work (i.e. as it has for A. cervicornis), and keep them safe from COTS; even with the wave surge, perhaps lines could be strung across the narrow grooves.  I have lots of long-liner monofilament at hand, which would minimize surge drag.

Dean Jacobson
College of the Marshall Islands

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