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Reef Monitoring

A reef survey and monitoring programme was established during the first Semporna Islands Project, with the aim of providing baseline data and information for management. Monitoring will be continued and expanded to provide a means of determining whether progress is being made towards meeting the goals for the Park.

Over 220 reef sites around the Semporna Islands were surveyed during the period 1998-2004 (prior to the Park being established) by marine biologists and volunteer divers from the Marine Conservation Society (UK) in collaboration with Sabah Parks. The surveys included mapping and biodiversity assessment and included all habitats from shallow water to the lower slope (30-40m depth). As a part of these surveys, records were made of the distribution and abundance of reef fish utilised by fishermen, and of invertebrates of value such as giant clams.

In addition to these broad-scale surveys, data have been collected from 4 ‘Reef Check’ sites (1998, 1999, 2000, 2004) and a further seven permanent reef monitoring sites (2000-2006 inclusive). The data from these sites provides baseline information on the status of the reefs in the absence of protection. Even though the Park was gazetted in 2004, active management is not yet in place and there have been no restrictions on fishing. The only exception is one section of reef at the eastern end of the Bodgaya lagoon, where there has been very limited fishing for several decades for security reasons (to protect a Pearl Farm: now no longer operating).

The monitoring sites were selected to represent the range of fringing reef habitats occurring in the Park, and include sheltered lagoonal sites as well as outer, clear-water sites (Mantabuan and Sibuan). Another factor in the selection process was to ensure that each of the proposed Management Zones was represented (i.e. General Use Zone, Conservation Zone and Preservation Zone).

 

Mantabuan Line 2001 © Elizabeth Wood
Mantabuan Line 2001 © Elizabeth Wood

The monitoring sites reflect the variation in condition of the reefs in the Park, with live hard coral ranging from 72% to 6%. The other notable feature of the reefs is the high amount of coral rubble at several of the sites (over 50%). In the absence of historical data, it is not possible to say whether the rubble has been produced by fish blasting, storms or other rubble-generating events, such as death and collapse of corals following predation by crown-of-thorns starfish. However, fish blasting is endemic and has without doubt had a significant impact on coral cover.

The surveys to date show low abundance of high and medium value fish and invertebrates targeted by fishermen and very few fish over 30cm in length. Mean density of reef fish such as groupers and rock cod, snappers, emperors and sweetlips is typically less than one individual per family per 100m 2, and at several sites none was recorded, indicating heavy and/or persistent fishing pressure. Higher numbers of these predatory fish might have been expected at the lagoon site where there has been little or no fishing for decades, but the environmental regime here (low energy; virtually no currents) may not be favourable.

Over-exploitation of invertebrates in the TSMP is illustrated by the low density of giant clams. The largest giant clam (Tridacna gigas) has been made locally extinct through over-collecting, and the mean density of other species at the permanent monitoring sites is 0.27 per 100m2, except in the protected Bodgaya lagoon, where there are ten times that number.

 

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