[Coral-List] Listing Criteria Observation

[Douglas Fenner]

    Most predation by parrotfish and other fish on coral produces
superficial feeding scars, with living tissue remaining below the scar.
 The tissue then recovers and regrows the damaged area.  I don't think I
have ever seen a parrotfish or puffer feeding scar that died, that would be
quickly colonized by turf algae and easily seen.  There are fairly rare
cases in the Pacific in which some fish focuses its biting on some table
coral, and reduces it to stubs, but the stubs are still alive.  I am not
sure about the parrotfish "focused biting" in the Caribbean, I've seen
photos of damage on Montastrea annularis, I believe.  But for the vast
majority of parrotfish biting, the coral recovers.  It is, in effect, much
like cows eating grass, it is grazing, from which the grass or coral
recovers.  It does cost the coral some energy to heal those damaged areas
(as it does for the grass), but from what I've seen, most of the time it is
quite minor, and most coral colonies are not grazed.  It is quite different
from a Barred Owl killing and eating a Spotted Owl.
     In the Pacific, there is one species of parrotfish, the bumphead
parrotfish, which regularly eats mouthfuls of live coral.  It's about half
their diet.  Because they are big, up to 4 feet long and 46 kg if I
remember, they are often targeted by fishers.  They are also easy to spear
at night as they sleep together as a school, at the same place night after
night, out in the open or partway in holes that are too small for them to
completely fit into.  They have declined in numbers, even gone locally
extinct some places, and in fact were petitioned for endangered species act
listing, but that petition was recently denied.  Using the figures given in
the summary for the NMFS report, I calculated that their estimates of
population indicate the population of these fish has decreased to between 3
and 9.6% of their original numbers, by their estimates.
     So not to worry, fishermen are already doing what you propose, and
reducing parrotfish populations on most reefs.  Parrotfish damage coral far
less than you suggest, and the other causes of damage to corals are vastly
greater, according to both the Reefs at Risk report, and the extensive NMFS
Status Report on the 82 coral species.  Take a look at the list of major
threats to coral reefs on either of those, or any other listing of major
threats to coral reefs, and look for parrotfish biting.  As others pointed
out, parrotfish also eat algae, which compete with coral, and they actually
do coral net good.  There was a paper by Mumby, Harborne et al that
documented that when an MPA in the Bahamas protected fish, the parrotfish
increased, algae decreased, and so coral cover increased.  If my memory
serves that was the conclusion.  So if you want to protect coral, you want
more parrotfish, not less.
     Is the way to protect endangered corals to ignore the documented
factors that cause the vast majority of the coral mortality, and focus only
on a very minor natural factor that doesn't even kill the coral, which was
present in greater amount before humans started impacting reefs, present
for millions of years without causing any documented coral extinctions?
 You're the geologist, how many millions of years have parrotfish been
grazing on corals?  How many coral species have been documented to have
gone extinct in the fossil record from parrotfish grazing?  I hazard a
guess, none.
Cheers,  Doug


On Wed, Dec 19, 2012 at 7:48 AM, Eugene Shinn <eshinn at marine.usf.edu> wrote:

> Steve, I know Parrot fish are a delicacy in the Pacific. They are
> protected in the Fla Keys and at anytime of day you can watch them
> biting chunks out of live coral especially Montastrea sp. Once they
> are listed we might want to consider spearing them to protect the
> coral from" harm." Since it was discovered that the listed Spotted
> Owl in old Growth Forests is declining due to predation by Barred
> Owls  the Fish and Wild Life Service is shooting the Barred Owls. If
> it works for Spotted Owls maybe it will work for corals...Outrageous
> eh? Well who knows what the future will bring in the world of
> government regulations and unintended consequences. Gene
> --
>
>
> No Rocks, No Water, No Ecosystem (EAS)
> ------------------------------------ -----------------------------------
> E. A. Shinn, Courtesy Professor
> University of South Florida
> College of Marine Science Room 221A
> 140 Seventh Avenue South
> St. Petersburg, FL 33701
> <eshinn at marine.usf.edu>
> Tel 727 553-1158----------------------------------
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