Holy Batfish Robin..... This article is a ray of sunshine in the
overwhelming atmosphere of doom and gloom surrounding corals of all
kinds these days - and a warning that we have SO much to learn, and that
habitat destruction or degredation in one place (in this case mangrove
swamps) can lead to disssaster in other places.

http://www.coralcoe.org.au/news_stories/batfish.html

Batfish to the Rescue

A masked marauder has emerged unexpectedly from the ocean to rescue a
dying coral reef from destruction in the nick of time.

With the dramatic flair of comic-book superhero Batman, a batfish has
saved a coral reef that was being choked to death by seaweed – although
the fish was never previously known as a weed-eater.

Scientists at the ARC Centre of Excellence for Coral Reef Studies
(CoECRS) who were studying how coral reefs are lost to weed were
astonished when, after removing a cage from a particularly weedy bit of
reef, the rare batfishes emerged out of the blue and cleaned up most of
the weed.

“Worldwide, coral reefs are in decline,” says Professor Dave Bellwood of
CoECRS and James Cook University. “Commonly this takes the form of the
coral being smothered by weedy growth, a transition known as a
phase-shift which is very hard, if not impossible, to reverse.”

“Research internationally has found that a major factor in this shift is
the over-fishing of weed-eaters like parrot and surgeon fish – which
normally keep the coral clean of weedy growth.”

Prof. Bellwood and colleagues Prof. Terry Hughes and Andrew Hoey were
testing a weed-infested patch of coral near Orpheus Island on
Australia’s Great Barrier Reef to see whether local herbivorous fish
could restore it to a normal state.

The ensuing action was captured on underwater TV cameras. When the cage
was removed from a particularly weedy patch, local herbivores pecked at
it but made little impression on the dense growth of sargassum weed.

“Then these batfish showed up and got stuck into it. In five days they
had halved the amount of weed. In eight weeks it was completely gone and
the coral was free to grow unhindered,” Prof. Bellwood explains.

The turnaround was due mainly to one species of batfish, /Platax
pinnatus/, which is comparatively rare on the GBR and was thought to
feed only on invertebrates.

The event surprised the scientists in two ways, he says. First, it
showed that the species one would normally expect to “mow the weeds” may
make little impression on a heavily-overgrown reef, dashing researchers’
hopes that herbivores may be a way to restore heavily weed-infested reefs.

And second, it shows that in nature, help can come from a totally
unexpected quarter – from a fish that itself may be at some risk.

“Batfish represent a ‘sleeping functional group’, meaning they are
capable of performing a vital role in the life of the reef, but do so
only under exceptional conditions,” Prof. Bellwood says.

“/Platax/ are relatively rare on the Great Barrier Reef and currently
have no specific legal protection. They are vulnerable because their
large size makes them attractive to spear-fishers, while they depend as
young fishes on coastal mangroves which are in decline in many areas.

“Indeed, the resilience of inshore GBR reefs may be closely tied to the
fate of mangroves and their suitability for batfish recruitment.”

Batfishes may be one of the last intact herbivore populations capable of
reversing serious weed overgrowth of inshore coral reefs, he adds. The
reef has already all-but lost one major group of weed-mowers, the
dugongs, while another – green turtles – is seriously endangered.

“If /Platax /is the last grazer of dense weedy stands on inshore coral
reefs and it goes into decline, the capacity of these reefs to recover
from phase-shifts could be lost.”

For scientists and reef managers, the batfish has thrown up a new
challenge – how to identify other ‘sleeping functional groups’ that may
prove lifesavers for the reef, but whose habits and abilities we as yet
know nothing about.

*Article*
Bellwood,DR; Hughes, TP and Hoey, AS. “Sleeping Functional Group Drives
Coral-Reef Recovery"
<http://www.current-biology.com/content/article/abstract?uid=PIIS0960982206023670>.
published in Current Biology, Vol 16, 2434-2439, 19 December 2006.
www.current-biology.com

- Ross Mayhew.



>

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