#Status of Coral Reefs 2002 - International Coral Reef Action Network

Status of Coral Reefs of Australasia
OVER- FISHING OF TROCHUS AND BÊCHE-DE-MER OFF WESTERN AUSTRALIA
Stocks of trochus and bêche-de-mer have been heavily fished on many of the world’s
reefs over the last 100 years. Bêche-de-mer, also known as holothurians, trepang, or
sea cucumbers, have been fished for centuries by Indonesians off the northwest of
Australia by reef walking or by shallow free diving. The preferred species are Holothria
nobilis (black teat fish), Holothuria fuscogilva (white teat fish) and Thelenota ananas
(prickly red fish). The collected animals are cleaned, boiled, and sun-dried or simply
cleaned and salted. Bêche-de-mer is high in protein, but its value is related more to the
belief that it is an aphrodisiac. The large marine snail, Tectra niloticus (trochus shell) is
collected in a similar way, but the meat is discarded, because the value is in the
lustrous shell, which is used to produce buttons, jewellery, ceramics, ornaments,
cosmetics and metallic paints. These are sold in Asia, Europe and America. Extensive
surveys of coral reefs of north-west Australia (Ashmore, Cartier, Scott Reefs) have
found low, to very low densities of trochus and bêche-de-mer at most locations. This
is indicative of over-exploitation that has lowered breeding stock densities. For
example, trochus densities on heavily fished northwest Australian reefs are 0.2 to 7.5
individuals per hectare compared to 45 – 500 individuals on fished and unfished reefs
in other regions. The most commercially valuable species of trochus and bêche-de-mer
are now only found at 18-35m depth, beyond the reach of snorkel divers. Management
strategies are now being implemented to protect remaining stocks on these isolated
coral reefs. From Luke Smith, l.smith@aims.gov.au
of the 1990s. In 1995, Imperieuse Reef, the most southern reef of the Rowley Shoals,
suffered significant cyclone damage. Average cover on reef slope sites before the cyclone
was 64% and was reduced to 11%. Many branching Acropora species have become almost
locally extinct, dropping from 50% to less than 1% after the storm. In the 6 years following
the cyclone, live coral cover has rapidly recovered to 42%. The Department of Conservation
and Land Management (CALM) has a long-term monitoring program (58 permanent sites)
at the Rowley Shoals Marine Park, and developed the Rowley Shoals Management Plan.
Cocos (Keeling) Island Reefs: These islands are extremely isolated with a small human
population. Consequently, localised anthropogenic impacts on the fringing reefs are
minimal. In the past, the atoll lagoon has been periodically exposed to long periods of flat
calm weather that has caused the water to stagnate and become anoxic. This has resulted
in major mortality events of the resident coral community. In addition, crown-of-thorns
starfish are, at times in high numbers but don’t have a major impact on the coral
communities. In 1998, Cocos escaped the major bleaching event that affected much of the
Indian Ocean, however the reefs were affected by bleaching in 1996.
The Dampier Archipelago and Monte Bello Islands: Coral bleaching affected many reefs on
the inner part of Dampier Archipelago in 1998 and presently these reefs are recovering.
Other than these impacts, there is no evidence on human impacts to these reefs. They are
managed and monitored by CALM, which is planning for the establishment of two proposed
State Conservation Reserves to include the Dampier Archipelago/Cape Preston Marine
Conservation Reserve and the Montebello/Barrow Islands Marine Conservation Reserve.
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