Reef Tribe Join The Reef Tribe

Reef Map · Visayas

Apo Island, Negros and Siquijor

Southern Negros Oriental, Siquijor and the Bohol Sea margin

About 1,827 words · 27 numbered sources · Updated 2026-11-13

The birthplace of community no-take marine reserves in the Philippines. More than four decades of Silliman University monitoring at Apo and Sumilon islands make this one of the best long-term natural experiments in coral reef fisheries science anywhere.

Geography and reef types

This region covers the southern coast of Negros Oriental, from Dumaguete through Dauin, Zamboanguita and Siaton, together with the islands of Apo and Siquijor and, across the strait, Sumilon Island off southern Cebu. It sits in the central Philippines at the meeting of the Bohol (Mindanao) Sea, the Sulu Sea and the Tañon Strait. The reefs are mostly narrow fringing reefs on steep volcanic and limestone shores. Small offshore islands such as Apo and Sumilon have reef flats that drop to coral-covered slopes, and the mainland coast mixes coral patches with sand, seagrass and algal beds.

Apo Island is a small volcanic island off Zamboanguita. The protected landscape and seascape declared around it in 1994 covers about 691 ha, almost all of it sea 12. Siquijor is a raised limestone island ringed by fringing reef, and Sumilon is a small coralline island off Oslob. The region is monsoonal. Seasonal reversals of the surface currents help shape where larvae disperse, as genetic studies along this coast show 3.

Biodiversity

The region lies close to what Carpenter and Springer identified as the "center of the center" of marine shore-fish biodiversity. Their analysis of the distributions of 2,983 species places the global peak in the central Philippine islands 4. A later study by researchers from UP Diliman, UP Mindanao and Old Dominion University found that exploitation has depleted reef-fish species richness in the Visayas, even within this epicentre. It argued that well-managed protected areas can recover local richness when paired with stronger fisheries management 5.

The best-documented fish assemblages are those at Apo and Sumilon. Russ and colleagues identified 13 trophic groups at these sites. Large planktivores often made up more than half of total fish biomass, and generalist large predators were the group most clearly affected by reserve protection 6. Planktivorous unicornfish (Naso vlamingii) at Apo became a model species for studying spillover 7. Studies of coral disease across the central Philippines, including Negros Oriental and its marine protected areas, found that reefs with more diverse fish communities had less disease 8.

Threats

The main local threats, in rough order of documented impact, are:

  • Fishing pressure. Overfishing removes predators and other target species, as shown by the rapid declines whenever Sumilon's reserve was reopened 1415.
  • Typhoon and heat-wave damage. This often outweighs fishing effects on coral and the fish that depend on it 611.
  • Coastal development and dive tourism. Shoreline construction and diving along the mainland coast bring sediment, wastewater and anchoring pressure. We found no published, quantitative assessment of these pressures for this coast, which is itself a research gap.

The economic stakes are high nationally. White, Vogt and Arin estimated the losses caused by reef destruction in the Philippines and showed that destructive practices cost far more over time than they earn 16.

The Sumilon experiment shows how fragile protection can be. Twenty-five percent of Sumilon's reef was made a no-take reserve in 1974. When protection ceased in 1984, the biomass of target fish in the reserve fell by 42.7% and trap and gillnet catches by 40% within a year 15. After protection was restored from 1987 to 1991 and from 1995 to 2001, reserve fish biomass rose by 27.2% and catches outside rose by 26.9% 15. Opening and closing a reserve is therefore not neutral. Gains built over years can be lost in months.

Management and protected areas

Silliman University's Biology Department set up the Sumilon and Apo reserves with local communities in 1974 and 1982. The university managed Sumilon for ten years and Apo for twelve 17. At Apo, the Silliman University Marine Laboratory's Marine Conservation and Development Program, launched in 1979, created a community Marine Management Committee that took on day-to-day management 2. On 9 August 1994, Proclamation No. 438 declared Apo Island and its waters a Protected Landscape/Seascape of about 691 ha under the NIPAS Act. It explicitly prohibits destruction of the coral reef ecosystem 1. The area was later legislated through the Expanded NIPAS Act of 2018 (Republic Act 11038), and it is now governed by a Protected Area Management Board that includes local government, academe and community organisations 182.

The same law legislated the Tañon Strait Protected Seascape, between Cebu and Negros. At 534,589 ha it is by far the largest protected seascape on the national list 18.

The Apo and Sumilon reserves became national models. Alcala and Russ describe how these modest 1970s experiments fed an extraordinary expansion of community-based no-take reserves across the country, a "new people power revolution" in reef fisheries management 19. Most Philippine MPAs are set up and run by communities with their local governments. This has won local acceptance and met local fisheries and conservation goals, but most were not designed as parts of ecologically connected networks 20. A follow-up thesis by Horigue at James Cook University identified 40 MPA networks nationwide. It found that experts saw better enforcement, lower management costs and easier conflict resolution as the main advantages of scaling up. The main obstacles were low technical capacity, reliance on bridging organisations, lack of sustained funding and the absence of a shared vision 26.

The legal basis for this local model is national. The Philippine Fisheries Code (Republic Act 8550) provides that at least 15% of each municipality's coastal area, where applicable, be identified on the best available science and designated as fish sanctuaries. Local governments make these designations in consultation with fisheries and aquatic resource management councils (FARMCs) 27. The Apo model of a small, community-enforced no-take core next to fished reef is the template that many such sanctuaries copied 19.

Key research and studies

  • The Apo–Sumilon reserve experiments (1974 onward). Probably the longest-running, spatially replicated test of no-take marine reserves on coral reefs. Target-fish biomass rose 3- to 4.5-fold inside the reserves over 9–18 years and did not rise outside them 15. At Apo, the total catch of major fish families was 41.3% higher in 1998–2001 than in 1981, before the reserve 15.
  • Spillover. At Apo, the biomass of surgeonfish and jacks, which make up 40–75% of the island's fishery yield, tripled in the reserve from 1983 to 2001. Outside, it increased more within 200–250 m of the boundary than farther away. Hook-and-line catch per unit effort was 50% higher in 1998–2001 than in 1981–1986 14.
  • Density-dependent export. N. vlamingii density inside the Apo reserve tripled between 1983 and 2003 and levelled off after 15–20 years. Aggression among adults was 3.7 times higher inside than outside, which is consistent with crowding pushing fish across the boundary 7.
  • Decadal recovery times. Full recovery of large predatory fish needs decades of continuous protection. Models suggest 20–40 years to reach new steady states 2122.
  • Larval connectivity. Genetic parentage analysis of the butterflyfish Chaetodon vagabundus along about 90 km of coastline, by Silliman University, UP MSI, James Cook University and partners, matched 37 parent–offspring pairs. Thirty-five of these linked different reefs rather than showing self-recruitment, and 51% of dispersal events crossed municipal or village boundaries. Half of larvae were predicted to settle within 33 km of their origin 3. Abesamis's review for the National Academy of Science and Technology sets out what this means for designing networks of marine protected areas in the Philippines 23.
  • Coral health and fish diversity. Raymundo and colleagues found that coral disease prevalence was negatively correlated with fish diversity across central Philippine reefs, and that protected areas had more fish diversity and less disease 8.

Restoration work

The region's main contribution to restoration is protection-led recovery. Reserves that rebuild fish biomass, herbivory and spillover are themselves the restoration intervention, provided habitat damage from storms and heat is not overwhelming 610. Active restoration is newer.

In Maria, Siquijor, a 3D-printed clay reef was installed in the Minalulan Marine Sanctuary in late 2024. Silliman University's Institute of Environmental and Marine Sciences (SU-IEMS), led by director Dr Aileen Maypa, joined its monitoring on 5–6 July and 29 November 2025, working with the Swiss–German group rrreefs 24. The Coastal Conservation and Education Foundation (CCEF) reported seventh-month monitoring at the site in July 2025, with SU-IEMS, Davao Oriental State University, BFAR's Siquijor provincial office, DENR and the local government. It also listed securing permits among upcoming activities 25. These are early results, and peer-reviewed outcomes have not yet been published.

Open research questions

  1. Can reserves still rebuild fish when coral is lost more often? The Apo–Sumilon record shows coral cover now drives fish trophic structure more strongly than fishing 6. With heat stress at record levels in 2024 12, it is uncertain whether recovery times of 5–10 years can keep up with disturbance intervals.
  2. What is the right spacing for reserve networks? Larval dispersal kernels suggest closely spaced reserves, a few tens of kilometres apart 3. Testing this for corals, as well as fish, and across monsoon seasons is an open problem.
  3. Does active restoration add value on top of protection? Clay and other substrate trials in Siquijor 2425 need controlled comparisons with unrestored reserve and fished sites, using the long-term Apo–Sumilon designs as a template 15.
  4. Coral disease and fish communities. The link between coral-feeding butterflyfish and disease prevalence 8 is unresolved as a causal mechanism and matters for reserve outcomes.
  5. How do tourism and dive fees affect governance? Apo's management board and community committee 2 are a natural laboratory for studying how dive tourism revenue, enforcement and fisher welfare interact over time.

References

  1. Republic of the Philippines (1994). Proclamation No. 438, declaring Apo Island and its surrounding waters, Zamboanguita, Negros Oriental, a Protected Landscape/Seascape. https://lawphil.net/executive/proc/proc1994/proc_438_1994.html
  2. Coastal Conservation and Education Foundation (CCEF). MPA database: Apo Island Protected Landscape and Seascape. https://www.coast.ph/mpa-database/02/apo-island-protected-landscape-and-seascape/
  3. Abesamis RA, Saenz-Agudelo P, Berumen ML, Bode M, Jadloc CRL, Solera LA, Villanoy CL, Bernardo LPC, Alcala AC, Russ GR (2017). Reef-fish larval dispersal patterns validate no-take marine reserve network connectivity that links human communities. Coral Reefs 36: 791–801. Silliman University and UP Marine Science Institute. https://doi.org/10.1007/s00338-017-1570-0
  4. Carpenter KE, Springer VG (2005). The center of the center of marine shore fish biodiversity: the Philippine Islands. Environmental Biology of Fishes 72: 467–480. https://doi.org/10.1007/s10641-004-3154-4
  5. Nañola CL, Aliño PM, Carpenter KE (2011). Exploitation-related reef fish species richness depletion in the epicenter of marine biodiversity. Environmental Biology of Fishes 90: 405–420. UP Mindanao and UP Diliman. https://doi.org/10.1007/s10641-010-9750-6
  6. Russ GR, Rizzari JR, Abesamis RA, Alcala AC (2021). Coral cover a stronger driver of reef fish trophic biomass than fishing. Ecological Applications 31: e02224. Silliman University and James Cook University. https://doi.org/10.1002/eap.2224
  7. Abesamis RA, Russ GR (2005). Density-dependent spillover from a marine reserve: long-term evidence. Ecological Applications 15: 1798–1812. https://doi.org/10.1890/05-0174
  8. Raymundo LJ, Halford AR, Maypa AP, Kerr AM (2009). Functionally diverse reef-fish communities ameliorate coral disease. Proceedings of the National Academy of Sciences 106: 17067–17070. https://doi.org/10.1073/pnas.0900365106
  9. Licuanan WY, Robles R, Reyes M (2019). Status and recent trends in coral reefs of the Philippines. Marine Pollution Bulletin 142: 544–550. De La Salle University. https://doi.org/10.1016/j.marpolbul.2019.04.013
  10. Russ GR, Miller KI, Rizzari JR, Alcala AC (2015). Long-term no-take marine reserve and benthic habitat effects on coral reef fishes. Marine Ecology Progress Series 529: 233–248. https://doi.org/10.3354/meps11246
  11. Bucol AA (2014). Typhoon-driven coral–algal phase-shifts in southern Negros Oriental, Philippines. e-Journal Budidaya Perairan 2(3). https://doi.org/10.35800/bdp.2.3.2014.5698
  12. NOAA Coral Reef Watch. Regional Virtual Station time series: Eastern Philippines (1985–present). https://coralreefwatch.noaa.gov/product/vs/data/eastern_philippines.txt
  13. NOAA Coral Reef Watch. Methodology, product description and data availability for the daily 5 km products. https://coralreefwatch.noaa.gov/product/5km/methodology.php
  14. Russ GR, Alcala AC, Maypa AP, Calumpong HP, White AT (2004). Marine reserve benefits local fisheries. Ecological Applications 14: 597–606. Silliman University. https://doi.org/10.1890/03-5076
  15. Alcala AC, Russ GR, Maypa AP, Calumpong HP (2005). A long-term, spatially replicated experimental test of the effect of marine reserves on local fish yields. Canadian Journal of Fisheries and Aquatic Sciences 62: 98–108. Silliman University. https://doi.org/10.1139/f04-176
  16. White AT, Vogt HP, Arin T (2000). Philippine coral reefs under threat: the economic losses caused by reef destruction. Marine Pollution Bulletin 40: 598–605. https://doi.org/10.1016/S0025-326X(00)00022-9
  17. Alcala AC (2017, published 2021). Apo Island and Sumilon Island marine reserves and beyond. Transactions of the National Academy of Science and Technology 39. Silliman University. https://doi.org/10.57043/transnastphl.2017.1063
  18. Republic of the Philippines (2018). Republic Act No. 11038, Expanded National Integrated Protected Areas System Act of 2018 (schedule of protected areas). https://elibrary.judiciary.gov.ph/thebookshelf/showdocs/2/84999
  19. Alcala AC, Russ GR (2006). No-take marine reserves and reef fisheries management in the Philippines: a new people power revolution. Ambio 35: 245–254. https://doi.org/10.1579/05-A-054R1.1
  20. Horigue V, Aliño PM, White AT, Pressey RL (2012). Marine protected area networks in the Philippines: trends and challenges for establishment and governance. Ocean & Coastal Management 64: 15–26. UP Marine Science Institute. https://doi.org/10.1016/j.ocecoaman.2012.04.012
  21. Russ GR, Alcala AC (2004). Marine reserves: long-term protection is required for full recovery of predatory fish populations. Oecologia 138: 622–627. https://doi.org/10.1007/s00442-003-1456-4
  22. Russ GR, Alcala AC (2010). Decadal-scale rebuilding of predator biomass in Philippine marine reserves. Oecologia 163: 1103–1106. https://doi.org/10.1007/s00442-010-1692-3
  23. Abesamis RA (2018, published 2022). Connectivity of coral reefs and other nearshore habitats: implications for marine resource management in the Philippines. Transactions of the National Academy of Science and Technology 40. Silliman University. https://doi.org/10.57043/transnastphl.2018.1084
  24. Silliman University (10 December 2025). SU-IEMS partners with Swiss-German groups for innovative coral reef restoration research. https://su.edu.ph/news/su-iems-partners-with-swiss-german-groups-for-innovative-coral-reef-restoration-research/
  25. Coastal Conservation and Education Foundation (8 July 2025). 7th-month monitoring of the artificial clay reef in Minalulan MPA. https://www.coast.ph/ccef-news/07/7th-month-monitoring-of-the-artificial-clay-reef-in-minalulan-mpa/
  26. Horigue V (2014). Scaling up to form marine protected area networks: the role of coordination of initiatives and institutional collaborations in the Philippines. PhD thesis, James Cook University. https://researchonline.jcu.edu.au/39883/1/39883-horigue-2014-thesis.pdf
  27. Republic of the Philippines (1998). Republic Act No. 8550, The Philippine Fisheries Code of 1998 (Section 81, fishery reserves, refuge and sanctuaries). https://lawphil.net/statutes/repacts/ra1998/ra_8550_1998.html

Every source above was opened and checked when this page was written. Philippine university authorship is noted where it applies. Figures are quoted from the cited source and are not independently re-measured. This page is a research overview, not legal or management advice.

Other regions