[Coral-List] Reef Substrate competition

Ernesto Weil eweil at caribe.net
Mon Aug 7 14:39:27 EDT 2006

Dear colleagues, just wanted to call your attention to a recent ms printed
in MEPS that we have available in pdf format for those interested. 

López-Victoria M, S Zea and E Weil (2006). Competition for space between
encrusting excavating Caribbean sponges and other coral reef organisms.
Mar.Eco.Prog.Ser. 312:113-121.

e-mail Dr. S. Zea szea at invemar.org.co



Ernesto Weil, Ph.D
Department of Marine Sciences
University of Puerto Rico
(787) 899-2048  ext. 241
(787) 899-5500  FAX

-----Original Message-----
From: coral-list-bounces at coral.aoml.noaa.gov
[mailto:coral-list-bounces at coral.aoml.noaa.gov] On Behalf Of Marie Kospartov
Sent: Thursday, August 03, 2006 5:22 AM
To: coral-list at coral.aoml.noaa.gov
Subject: [Coral-List] Latest assessment of Ashmore Reef and Cartier
Reservesnow available

Dear Colleagues, 

The latest assessment of marine communities at Ashmore Reef National
Nature Reserve and Cartier Island Marine Reserve (in the Timor Sea
north-west of Australia) is available at:  


Kospartov, M., Beger, M., Ceccarelli, D. and Richards, Z.  2006.  An
assessment of the distribution and abundance of sea cucumbers, trochus,
giant clams, coral, fish and invasive species at Ashmore Reef National
Nature Reserve and Cartier Island Marine Reserve: 2005.  Report prepared
by Uniquest Pty Ltd for the Department of the Environment and Heritage.  

A brief summary of the report is presented below. For further
information on the report please contact: Marie Kospartov
<marie.kospartov at mailservice.ms> or Daniela Ceccarelli
<dmcecca at bigpond.net.au>. For further information on the Reserves,
please contact Nathan Harris at the Australian Department of the
Environment and Heritage <nathan.harris at deh.gov.au>. 

Ashmore and Cartier are open ocean platform reefs, located on the North
West Sahul Shelf in the Timor Sea between Western Australia and
Indonesia. The Reserves are of great conservation significance due to
their high diversity, unique oceanic location, geomorphology and
cultural heritage. The Reserves are managed by the Australian Department
of the Environment and Heritage. Traditional Indonesian fishers have
visited reefs and shoals in the Ashmore and Cartier area for hundreds of
years to collect sea cucumbers and trochus shells. Harvest of these
species is now prohibited in the Ashmore and Cartier Reserves, as is
finfishing except for immediate consumption in a restricted part of
Ashmore Reef. Monitoring surveys are conducted approximately every two
to three years to assess the distribution and abundance of trochus, sea
cucumbers, giant clams, fish and corals. 

Our September 2005 surveys recorded highly patchy distributions of
trochus, sea cucumbers and tridacnid clams. Trochus densities at Ashmore
and Cartier averaged 37.7 and 20.3 individuals per hectare,
respectively, across all habitats surveyed. Compared to previous
surveys, trochus were found in slightly lower densities at Ashmore and
slightly higher densities at Cartier.  Overall, there was no convincing
evidence of an increase in trochus densities since the previous surveys
in 2003, but there was also no strong evidence that populations had
declined further. 

Sixteen species of sea cucumber were found at Ashmore, and six species
were recorded at Cartier.  The high-value species Holothuria nobilis and
H. fuscogilva were found in very low densities similar to those found in
2003.  The other two high-value species potentially to be found in the
Reserves, H. scabra and H. timana, were again not recorded, suggesting
local extinction of these species from overexploitation.  The most
abundant sea cucumbers at Ashmore Reef were those that are able to
reproduce both sexually and asexually through fission, most of which are
of low commercial value (Holothuria atra, H. leucospilota, H. edulis and
the higher value Stichopus chloronotus). Densities varied greatly
between habitats and between species, but were very low for most species
(estimated at less than six individuals per hectare for most species in
most habitats). Despite small variations in the densities of some
species, the overall community structure and relative densities of sea
cucumbers in the Reserves was similar to those recorded in 2003.

Giant clams were not common in the Reserves, but densities were higher
at Ashmore than at Cartier, averaging 17.6 and 9.3 individuals per
hectare, respectively.  Tridacna maxima and T. squamosa, found primarily
in reef crest habitats, numerically dominated the clam assemblages.
Hippopus hippopus was also present in relatively high densities,
particularly on the reef flat at Cartier Island. Densities of the
largest of the tridacnid clams, T. gigas, have been reported as
extremely low since 1986, and this species was extremely rare during the
current survey. 

Finfish communities were diverse and abundant, but coral communities
appeared to have suffered from repetitive severe bleaching events.
Extensive coral mortality, which probably occurred several years ago
during the 1998 and 2003 bleaching events, was evident and very few new
coral recruits were observed. The sheltered northern sides of both reefs
had higher diversity and abundance of fish, corals and some
invertebrates. These areas may act as refugia and provide a local source
of larvae to assist the reefs to recover from bleaching and overfishing.
Maintenance of the current level of closures and enforcement were
recommended (with particular attention given to the northern sides of
the reef), and suggestions were provided for a permanent standardized
monitoring programme. We also suggested considering the viability of
restocking sea cucumbers and giant clams of high commercial value, which
are severely depleted in the Reserves. 

Marie Kospartov
Consulting Marine Ecologist

Email: marie.kospartov at mailservice.ms
Phone/Fax: +64 3 329 3350

Postal address:
58 Marine Drive
RD1 Lyttelton, 8033
New Zealand

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