The Lihou Reef National Nature Reserve (Reserve) is one of two
protected areas in the Coral Sea region. The Reserve is located some 400
kilometres east of Townsville, Queensland. The Reserve was declared on
16 August 1982 and the first plans of management prepared under the
National Parks and Wildlife Conservation Act 1975, came into effect
in 1989. The reserve is one of twelve Marine Protected Areas (MPAs)
managed by the Marine and Policy Branch of the Department of the
Environment and Heritage (DEH). The Australian Institute of Marine
Science (AIMS) conducted fish, benthic and bęche-de-mer surveys in the
Reserve, 15-18 March 2004.
One hundred species of hard coral were recorded in the Reserve
compared to 99 at the Coringa-Herald Reserve in 2003. Coral cover was
low (7.9%) and consistent with a reef recovering from a disturbance. At
the time of the surveys, a severe bleaching event was in progress.
Bleaching of hard corals was observed at all sites and at the Reserve
level it was estimated that 65% of the hard coral cover was bleached.
Bleaching was uneven among coral families with the Acroporidae most
affected, followed by the Pocilloporidae. Faviidae and Poritidae were
least affected. The high levels of bleaching in the Acroporidae were
consistent across all reefs. A few hard coral species did not appear to
be affected by the bleaching, including Coscinarea columna and
Porites lichen, while some species showed a low level of bleaching
including Pocillopora edyouxi, Leptastrea inequalis, Turbinaria
spp., Goniopora spp. and Astreopora spp.
The majority of hard coral species had unusually small colony sizes.
There were few hard coral colonies greater than 50cm diameter. The small
size of coral colonies and low overall coral cover is interpreted as an
indication of a recent large-scale disturbance event. The occurrence of
another large-scale disturbance raises serious concerns that some coral
species will become severely depleted. There is evidence that this has
already occurred as a result of the previous disturbance event. No
crown-of-thorns starfish (COTS) were observed during the surveys and
there was no sign of damage to corals from COTS activity. There were no
signs of damage to corals from coral disease.
Multivariate analysis has revealed that the fish community at Lihou
Reef Reserve was very similar to that encountered at the Coringa-Herald
Reserve in 2003. However, this ‘Coral Sea’ community was quite distinct
from the community encountered at Elizabeth Reef in 2003. This
separation was largely driven by the presence of several temperate water
species at Elizabeth Reef, most notably Prionurus maculatus,
Chromis hypsilepis and Chrysiptera notialis. Three species of
coral trout (Plectropomus laevis, P. leopardus and
Variola louti) were recorded during the surveys at Lihou Reef
Reserve. Plectropomus laevis dominated the upper size class
frequency distribution to the exclusion of P. leopardus.
The only previous survey of Lihou Reef was conducted in 1984. A
comparison between the 1984 data and this survey provides some evidence
for a decline in cover of hard coral, soft coral and sponges. In
contrast, numbers of the commercially valuable coral trout species
appear to have increased slightly between 1984 and 2004.
This report represents the first published surveys of bęche-de-mer in
the Reserve. Only four bęche-de-mer species were observed. They were the
commercially important Holothuria whitmaei (nobilis), along with
Holothuria atra, Bohadschia argus and Thelenota ananus.
The densities of H.
whitmaei observed in the Reserve was similar to those observed in
the Coringa-Herald Reserve in 2003. They were clearly lower than the
densities observed at Elizabeth Reef in 2003.
It is clear that the reefs of the Lihou Reef National Nature Reserve
are under significant pressure, especially from the effects of coral
bleaching and cyclones. The bęche-de-mer populations in the Coral Sea
are also under heavy pressure as evidenced by the decline in catch rates
in the local fishery. This highlights the importance of maintaining a
proportion of the reefs in the region as strict nature reserves (at
present: Coringa-Herald NNR and Lihou Reef NNR) in an attempt to
maintain the long-term viability of these habitats, ecosystems and
native species, by preventing additional human impacts. This is a key
objective of the management plan for both the Lihou Reef NNR and the
Coringa-Herald NNR.
