Parrotfish, again

James M. Cervino cnidaria at
Fri Sep 19 07:48:46 EDT 1997


FROM: T. Goreau, J. Cervino, K. DeMeyer, I. Nagelkerken, R. Hayes,
G. Smith, M. Goreau

We will be delighted to look at Andy Bruckner's photos, and welcome
>the constructive exchange. We have filmed many parrotfish bites that
>appeared to be on corals, but on direct inspection of the scars, turned out
>to always be on algae patches. RWD is turning the tops of the Montastrea
>annularis heads into algal turf patches, and the parrotfish are
>specializing in them with gusto because these are the major food resource
>available. There is no doubt that they will once in a while nibble at
>coral, but this is common only where there is not enough algae (e.g. in
>oligotrophic reefs in the Pacific and Indian Ocean, Cayman, and Turks and
>Caicos, and until recently, Bonaire). This behaviour is often seasonal
>territorial marking on isolated heads by large males. We have always seen
>the coral to recover afterwards, without spreading necrosis. This is why we
>first evaluated the parrotfish hypothesis at the very start of our work,
>and concluded that it was not the cause of RWD. Nor have we seen them
>attack edges of Colpophyllia natans tissue, although we have repeatedly
>seen them bite algal turf on the dead parts of the colony within a
>centimeter of living remnants. The fact is that we are seeing beautiful
>Colpophyllia heads hundreds of years old vanish in weeks on a large scale,
>and this is certainly new.

In the buckets and aquaria : the RWD was on the tops of annularis before I
placed it in the tank, and some of the depressions I have are more than an
inch. Each ridge and valley on the C. natans is depressed, however it is
important to note that if it were Parrot fish, the fish would leave bite
marks along the valley and ridge. Just think of the ridge and valley eroded
down in size, there is no scraping out of the normal direction of the way
the valley and ridge fall or have been originally formed by the coral.  Any
bite or excavation marks by a Parrot fish would disrupt the normal pattern
of the valley and ridgedirection. And on M. annularis the septa and caylex
are not disrupted in direction, just eroded and depressed.  It is not
possible that fish could do such damage to miles and miles of coral heads
and not be observed? This would have looked like a massive attack by
schools of fish! All of the Parrot fish scientists completly out rule RWD
the result of Parrot fish grazing.  We do see on occasion Parrot fish eat
algae, however not deep excavation. I am marking my corals at the early
stages or shall I say signs of RWD and following the spread.

>         Jim Porter and Craig Quirolo, have just found RWD in Florida. They
>report that it was completely unlike anything they had ever seen before,
>and that it had a distribution and appearance which could not possibly have
>been due to parrotfish. The same conclusion has been reached independently
>by more than a dozen researchers around the Caribbean, almost all of whom
>at first sight thought they were seeing the biggest parrotfish bite of
>their lives!
>        With regard to distribution we now have photographs, histological
>samples, and microbial cultures from sites all around the Caribbean (St.
>John, Grenada, Tobago, Venezuela, Bonaire, Curacao, Aruba, Colombia,
>Cayman, Mexico, and Florida) with the exception of the central area,
>including Puerto Rico and the Dominican Republic. This disease is moving so
>rapidly that we urge divers in that area to keep your eyes out for it. We
>are afraid that Puerto Rico and other parts of the Central Caribbean will
>not be far behind the affected sites all around the sides of the Caribbean.
>Once you see it you will have no doubt that it is new. We will pleased to
>have you join the group of researchers who have seen it and are tracking
>it. Our collective inputs will soon be out on the web, at an url to be
>posted here, which will contain photographs and distribution maps of all
>the Caribbean reef diseases.

Any replys send to cnidaria at, Tom is out in the field!

James M. Cervino
Marine Biologist
Global Coral Reef Alliance
124-19 9th ave, College Point NY 11356
Phone/Fax 718-539-8155

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