[Coral-List] Coral-List Digest, Vol 48, Issue 17
delbeek at waquarium.org
Wed Jun 20 21:42:04 EDT 2007
Austin Bowden-Kerby Travelling wrote:
> Hi Todd (and Andrew),
> I have been working with Acropora and Coraliophila snails and Hermodice fire worms for a long time in DR and Honduras and formerly in PR and Jamaica. Todd, for the sake of the corals, please remove all snails (and worms) from the Acropora colonies when you find them in your work, as a dozen or so snails will kill even a large colony in only a few months, and these corals are truly precious and as you know are mostly either gone or are still in the process of declining.
> Regarding your question- my experience is that spreading out the coral transplants is not always the best strategy, unless you have someone to do regular and frequent "coral gardening" - removal of snails and fire worms and the occasional weeding of seaweeds. If there are a lot of snails around on other corals, spreading them out may end up increasing the predation problem, but if the reef is mostly devoid of other corals, then spreading them out may work fine. The snails live on all sorts of corals (they love to lurk around the edges of brain corals and on Montastrea, and when very small they seem to prefer Agaricia), but they don't seem to be as devastating to those species with thicker flesh. However they seem to much prefer Acropora, and so if you spread your transplants out, the corals will almost for sure be attacked, as the snails leave the corals they are on and go for their preferred Acropora. Probably the most important thing that we have found is that the
> snails do not like to cross sand, so a better strategy is is to locate a reef spur surrounded by sand channels or a small patch reef on which to focus your restoration work, removing any snails you can find on other corals initially, but with the understanding that once the snails are under control, that new snails will not be able to readily move in from the surrounding reefs, although sometimes some very tiny ones appear later on, apparently settling out of the plankton. Fire worms will cross sand, so it is only a partial barrier, so the corals still need to be monitored for predators, but not as frequently. Reef balls on sand should also work very well as Acropora nurseries! It is my hypothesis that a lack of lobsters and trigger fish are the most important factors in the Coraliophila snail (and perhaps Hermodice fire worm problem). While trigger fish seem to effective controls on snail outbreaks on Acropora palmata, they don't seem to be as effective in
> controlling the snails on A. cervicornis, perhaps due to the species' branchiness. What this tells us is that no-take MPAs are the foundation of coral reef restoration- otherwise we are fooling ourselves. I believe that coral predation may have been underestimated as a primary factor in the demise of both species of Acropora, as it is quite easy to attribute fresh coral predation to coral disease (WBD). I have found that in all of our sites in all of the countries where we have worked over the past several years that predation is presently by far a much more severe problem for Acropora than coral disease is. If there is a problem with disease, it is sporadic, and often secondary to Stegastes damsel fish infestation (secondary to overfishing of groupers?) or to land based development and dirty water- so if possible stick to clean waters and avoid areas with these damsel fish. Based on Andrew's posting Hermodice fire worms may also be a vector for disease.... from what
> I have read, this has already been established for Coraliophila snails.
> I plan to get all of these and other findings and suggestions/opinions out in an Acropora restoration handbook in the coming year or so.
> Austin Bowden-Kerby, PhD
> Coral Gardens-Living Reefs
> Counterpart International
> Suva, Fiji; (679)331-3377
This brings up the issue of what preys on these snails naturally? I am
pretty sure that either there is a wrasse, puffer, crab or perhaps
hogfish that may prey on these snails. Has their population been
affected by the hurricane?
J. Charles Delbeek
Aquarium Biologist III
University of Hawaii
2777 Kalakaua Ave.
Honolulu, HI, 96815
(808) 923-9741 VOICE
(808) 923-1771 FAX
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