Reef Check News
Reef Check Concludes First Comprehensive Survey of Brunei Reefs
By Reef Check Executive Director, Dr. Gregor Hodgson
Reef Check recently completed work on the baseline Marine Protected Area (MPA) monitoring in Brunei, a small nation located on the north coast of the island of Borneo, in Southeast Asia. Located at the edge of the Coral Triangle near the world center of marine biodiversity, the reefs exhibit a very high biodiversity. Reef Check was requested by the Brunei Department of Fisheries (DOF) to carry out a survey of its coral reefs, most of which were placed inside a new network of MPAs that was implemented January 1, 2012. Each of the reefs located within the MPAs is a no-take fishing area. The baseline survey will allow the DOF to track changes and hopefully improvements in the health of the country’s coral reefs over time.
A team of six scientists from Reef Check International (RC), Reef Check Malaysia and the National University of Malaysia surveyed 36 reef sites in April 2012 using the Reef Check protocol augmented with video, still photographs and roving swims to document fish families. An additional 7 sites were previously surveyed in October and November 2011. These 44 sites covered all major reefs in Brunei waters and included sites from the three MPA areas, as well as Champion Oil Field which is currently not included in the MPA network.
A second and more detailed round of surveys was carried out in October 2012 that added a great deal of new information about the condition of Brunei’s coral reefs and species living there. For this set of surveys more information was obtained on the distribution of coral genera and non-coral invertebrates that are not part of a standard Reef Check survey. In addition, fish surveys were carried out to determine the distribution and abundance of target species of interest to fishermen and biomass of populations of food fish was calculated.
The October surveys confirmed the April findings that Brunei’s reefs are all structurally similar with a very low vertical profile and low relief due to geology and present day influences of freshwater, turbidity, sedimentation and wave action which all negatively affect the ability of corals to reproduce and grow in Brunei. Large (5 – 10 m diameter) “bommies” comprised of individual Porites coral colonies are found sporadically at most sites and provide habitat for resident reef fish including high value commercial fish such as Sweetlips (Haemulidae) and Grouper (Serranidae).
Reef Check indicator fish populations are quite low and most food fish are immature, indicating over fishing of these reefs. Enforcement of the no-take zones will be an important goal that will allow the reef fish populations to repopulate naturally.
The coral cover ranged from a low of 9% at Otter Shoal to a high of 76% at Abana Rocks. The average coral cover of about 40% is consistent with reefs in the region. Nutrient Indicator Algae is low at most reefs but reached as high as 15% at some reefs, indicating a lack of herbivory. For no apparent reason, there are almost no sea urchins on Brunei reefs, exacerbating the lack of herbivorous fish. Coral consuming Crown-of-Thorns Sea Stars (Acanthaster) and the gastropod Drupella are present but not abundant. Two invertebrate indicators for food collection – spiny lobster and giant clams – were recorded in low numbers and most were small to medium size. The low numbers of small size classes of giant clams recorded indicates that there is little successful reproduction and recruitment occurring on Brunei reefs. Therefore it may be necessary to introduce aquacultured clams to build up the populations to the size where they can begin to reproduce naturally.
Little trash was observed on Brunei reefs, however, ghost nets were found on almost all. At the Champion Oil Field sites, quite a lot of construction debris was found on most reefs. The underwater visibility during the surveys ranged from 6 to 20 m, and the water colour was typically green or yellow indicating a high density of phytoplankton.
Prior to the baseline survey, very little was known about many of the reefs of Brunei and there had never been a comprehensive survey done. Annual re-surveys of the reefs are recommended so changes due to the implementation of the MPAs can be assessed.