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Reef Map · Visayas

Danajon Bank, Bohol and Cebu

Central Visayas: the double barrier reef, Olango and the Cebu coasts

About 1,868 words · 29 numbered sources · Updated 2026-11-13

The only double barrier reef in the Philippines, ringed by more than a hundred thousand small-scale fishers, alongside the dive reefs of Panglao, Balicasag and Cebu. Decades of community marine sanctuaries, seahorse research and long-term monitoring meet heavy fishing pressure, blast fishing and the 2021 typhoon.

Geography and reef types

The central Visayas between Cebu and Bohol hold some of the most heavily used reefs in the country. The best-known feature is Danajon Bank off northern Bohol. Samonte et al. (2016) describe it as the only double barrier reef in the Philippines. It formed over the past 6,000 years and covers about 27,200 ha of reef, with 699 km of coastline across 17 municipalities in four provinces 1. Project Seahorse describes it as one of only six double barrier reefs in the world, running about 135 km along Bohol's western and northern coasts 2. It has three large reefs, clusters of smaller reefs and about 40 small islands. The outer barrier reefs and slopes have the richest coral growth. The inner reefs and lagoons are more turbid 1. Earlier geological work cited by Samonte et al. links the double barrier to unusual tidal currents and/or renewed subsidence after the outer barrier formed 1.

Elsewhere the region has fringing reefs and reef flats around high islands and low coralline islands. Panglao, Balicasag and Pamilacan off south-western Bohol face the Bohol Sea, and their sanctuaries are among the longest monitored in the country 3. Olango Island, 4 km east of Mactan, is a low limestone island with a wide coralline intertidal flat, seagrass and offshore reefs 4. The Camotes Islands lie in the Camotes Sea between Cebu and Leyte 21.

Biodiversity

Calumpong (2004) recorded 211 hard coral species on Danajon Bank. The bank also has sharks and rays, a large seahorse population and more than 2,000 ha of Rhizophora mangrove. It is an important feeding and roosting area for more than 20 bird species, including the threatened Chinese egret, as summarised by Samonte et al. 1. Project Seahorse calls Danajon the epicentre of seahorse fishing in the Philippines. The tiger-tail seahorse Hippocampus comes is taken there in a multi-species fishery 2,13. Olango Island is a Ramsar Wetland of International Importance (designated 1 July 1994, about 5,800 ha). Its information sheet calls it one of the most important staging areas for migratory shorebirds in the central Philippines. The site also includes mangroves, seagrass beds and offshore reefs 4.

Cebu itself is a fish-diversity hotspot. A DNA barcoding study of fish markets around the province sequenced 538 specimens from 393 species. Twelve species were new records for Philippine waters 5. The work was led by Taiwanese institutions with UP Cebu, UP Mindanao and Western Philippines University. Coral disease surveys by Silliman University across Cebu, Panglao, Olango, Bantayan, Pescador and Balicasag found Porites ulcerative white spot and coral tumours at high prevalence in some sites 6. In Camotes and nearby Leyte, surveys recorded ten coral species on the IUCN Red List or the EDGE list, including Pachyseris rugosa, Physogyra lichtensteini and four Turbinaria species 21.

Threats

  • Overfishing and destructive fishing. Fishing pressure is the main driver of Danajon's decline 1,12. Blast fishing is still a measurable cause of coral loss 8. Bacalso et al. (2016, with UP Cebu and ZMT) modelled the bank's municipal fisheries and found that shifting illegal fishing effort to legal gear could be profitable 14.
  • Seahorse and other targeted fisheries. Yasué et al. (2015) tracked seahorse sales at two sites from 1996 and 2005 to 2010. A community size limit increased the size of seahorses traded. The national ban on seahorse fishing from 2004 perversely led more fishers to sell seahorses, and later declines in catch probably reflected falling populations 13. O'Donnell, Pajaro and Vincent (2010) showed that ignoring fishers' recall of historical catches can understate extinction risk 15.
  • Typhoons. The December 2021 typhoon broke shallow reef flats and branching corals on exposed reefs around Panglao and Balicasag 3.
  • Tourism and coastal development. Gilutongan Marine Sanctuary off Cordova, Cebu, is a popular dive site after community restoration. Researchers have warned that mass tourism there is becoming a serious problem 16,17.
  • Disease and water quality. Silliman University surveys across the central Visayas found high prevalence of two Porites syndromes at some sites. Along a gradient centred on Dumaguete in nearby Negros, disease rose with human influence 6.

Management and protected areas

The region pioneered community marine sanctuaries. Pamilacan (1985), Balicasag (1986) and Doljo (1986) were among the early Bohol sanctuaries 3. On Danajon, Project Seahorse helped the village of Handumon set up its first MPA in 1995 and went on to help establish 35 community MPAs in the central Philippines. Most are no-take reserves, and the largest is the 245 ha Sinandigan MPA 18. Under the Expanded NIPAS Act (RA 11038), legislated protected areas here include the Talibon Group of Islands Protected Landscape and Seascape on Danajon (6,446.31 ha), the Panglao Island Protected Seascape (2,445.08 ha), the Camotes Island Protected Landscape and Seascape (1,436.98 ha) and the Olango Island Wildlife Sanctuary (1,382.29 ha) 19. Olango was first declared a wildlife sanctuary by Proclamation No. 903 in 1992 4.

Larger-scale management has also been tried. The USAID-funded Fisheries Improved for Sustainable Harvests (FISH) Project treated Danajon Bank as one ecosystem across municipal boundaries. It used MPAs, gear and effort limits, licensing, zoning and enforcement. It aimed to raise fish biomass by 10% over 2004 levels, and monitoring in 2006 and 2008 showed small improvements 12. Armada, White and Christie (2009) concluded that matching governance to the ecosystem's boundaries was the most important consideration 12. Bacalso, Juario and Armada (2013, UP Cebu) asked Danajon fishers to choose among management scenarios 20. Horigue's study of MPA networks included the Camotes Sea coastal resource management council as a collaborative network 22.

Benefits are not shared evenly. Kleiber, Harris and Vincent (2018) interviewed more than 500 people in 12 Danajon communities. MPAs were largely seen as a tool for men's subtidal fishing. Women, who mostly glean on intertidal flats, were less likely to report benefits or take part in decisions. In two communities, intertidal MPAs were moved or opened to allow gleaning 23.

The economic stakes are large. Samonte et al. (2016) put the total economic value of Danajon's marine resources at USD 6.27 million a year, or USD 59.6 million over 20 years at a 10% discount rate 1. An earlier valuation of the 112,000 ha Bohol Marine Triangle off south-western Bohol found that coral reefs generated about USD 1.26 million a year. Tourism and municipal fisheries made up most of its net benefits 24.

Key research and studies

  • Long-term sanctuary monitoring. CCEF's Bohol series from 1985 to 2023 is one of the longest in the country 3.
  • Ecosystem-based fisheries management. The FISH Project and its follow-up studies by UP Cebu researchers 12,14,20.
  • Seahorse science. Project Seahorse (UBC and ZSL) work on H. comes, MPAs, catch monitoring and fisher knowledge 2,13,15,18.
  • Multiple stressors. Selgrath et al. (2025) provide one of the clearest quantified links between blast fishing, fishing effort, MPAs and coral occurrence in the Philippines 8.
  • Economic valuation. Samonte et al. (2007, 2016), with CCEF and The Nature Conservancy 1,24.
  • Fish biodiversity. The Cebu barcoding library with UP Cebu, UP Mindanao and WPU 5, and UP Cebu's benchmark MPA surveys in Liloan 25.

Restoration work

Coral restoration in the region has been done mainly through government-funded pilot projects run by universities. Under DOST-PCAARRD's Filipinnovation coral reef restoration programme, the University of San Carlos (Cebu) and Bohol Island State University's Candijay campus ran a pilot in Panglao. They deployed 40 coral nursery units 26. Tagged transplants had about 80% survival, though survival fell where crown-of-thorns starfish and Drupella snails were present. Acropora nobilis grew about 5.8 cm a year 26. Restoration of the Gilutongan reef by the Cordova community is often cited as a turnaround, now challenged by tourist numbers 17.

DLSU researchers have warned that artificial reefs are costly, that reef rehabilitation costs far more than protection, and that artificial habitats should be used only in a few cases with management and monitoring 27. Mangrove planting shows the same lesson. On Olango and Banacon (Danajon) islands, single-species Rhizophora plantations on a limestone reef flat reached a steady state after about 60 years. They did not resemble natural forests, and their propagules spread into nearby natural stands 28. For Danajon, the evidence suggests the best returns come from controlling blast fishing and fishing effort, protecting compact reef patches inside MPAs 8, and siting any active restoration on sheltered reefs with strong enforcement 3.

Open research questions

  1. Recovery after 2021 and 2024. How have exposed Bohol and Cebu reefs recovered from the 2021 typhoon, and how much bleaching did the 2024 heat event cause on Danajon 3,10?
  2. Lagged fishing effects. Will cutting fishing effort now show up in coral cover only a decade later, as Selgrath et al. suggest 8?
  3. Seahorse populations. Are H. comes populations recovering in older Danajon MPAs, and how should the national ban be revised 13?
  4. Inclusive MPAs. How can intertidal gleaning by women be included in MPA design without weakening protection 23?
  5. Restoration that lasts. Which nursery and transplant methods survive crown-of-thorns and Drupella pressure in Bohol 26?
  6. Connectivity. How strongly are Danajon, Camotes, Olango and the Bohol Sea linked by larvae? Regional models suggest most larvae settle within a third of their maximum dispersal distance 29.

References

  1. Samonte GPB, Eisma-Osorio R-L, Amolo R, White A (2016). Economic value of a large marine ecosystem: Danajon double barrier reef, Philippines. Ocean & Coastal Management 122: 9–19. Coastal Conservation and Education Foundation. https://doi.org/10.1016/j.ocecoaman.2016.01.001
  2. Project Seahorse. MPA groundwork (Danajon Bank). https://projectseahorse.org/establishing-protected-areas/creating-protected-areas/mpa-groundwork/
  3. White A, Molina D, Delizo D Jr, Diaz R, Sabonsolin A (2024). Summary field report: "Saving Philippine Reefs" coral reef monitoring expedition to Bohol, 2023. Coastal Conservation and Education Foundation, Cebu City. https://www.coast.ph/publications/summary-field-report-saving-philippine-reefs-coral-reef-monitoring-expedition-to-bohol/
  4. Ramsar Convention. Information Sheet on Ramsar Wetlands: Olango Island, Philippines (site 656). https://rsis.ramsar.org/RISapp/files/RISrep/PH656RIS.pdf
  5. Huang W-C, Evacitas FC, Balisco RA, Nañola CL, et al. (2023). DNA barcoding of marine teleost fishes (Teleostei) in Cebu, the Philippines, a biodiversity hotspot of the Coral Triangle. Scientific Reports 13: 14867. UP Cebu, UP Mindanao and Western Philippines University. https://doi.org/10.1038/s41598-023-41832-9
  6. Kaczmarsky LT (2006). Coral disease dynamics in the central Philippines. Diseases of Aquatic Organisms 69: 9–21. Silliman University. https://doi.org/10.3354/dao069009
  7. Villarta KA, Campos WL, Beldia PD (2013). Spatial variability in reef habitat structure in southern central Philippines. Galaxea, Journal of Coral Reef Studies 15: 84–91. UP Visayas. https://doi.org/10.3755/galaxea.15.84
  8. Selgrath JC, Gergel SE, Vincent ACJ (2025; issue 2026). The influence of multiple stressors on the spatial distribution of corals. People and Nature 8: 342–358. University of British Columbia (Project Seahorse). https://doi.org/10.1002/pan3.70208
  9. Lavides MN, Polunin NVC, Stead SM, Tabaranza DGE, Comeros-Raynal MT, Dongallo JR (2009). Finfish disappearances around Bohol, Philippines inferred from traditional ecological knowledge. Environmental Conservation 36: 235–244. https://doi.org/10.1017/S0376892909990385
  10. NOAA Coral Reef Watch. Regional Virtual Station time series: Eastern Philippines (1985–present). https://coralreefwatch.noaa.gov/product/vs/data/eastern_philippines.txt
  11. NOAA Coral Reef Watch. Methodology, product description and data availability for the daily 5 km products. https://coralreefwatch.noaa.gov/product/5km/methodology.php
  12. Armada NB, White AT, Christie P (2009). Managing fisheries resources in Danajon Bank, Bohol, Philippines: an ecosystem-based approach. Coastal Management 37: 308–330. https://doi.org/10.1080/08920750902851609
  13. Yasué M, Nellas A, Panes H, Vincent ACJ (2015). Monitoring landed seahorse catch in a changing policy environment. Endangered Species Research 27: 95–111. https://doi.org/10.3354/esr00643
  14. Bacalso RTM, Wolff M, Rosales RMP, Armada NB (2016). Effort reallocation of illegal fishing operations: a profitable scenario for the municipal fisheries of Danajon Bank, Central Philippines. Ecological Modelling 331: 5–16. https://doi.org/10.1016/j.ecolmodel.2016.01.015
  15. O'Donnell KP, Pajaro MG, Vincent ACJ (2010). How does the accuracy of fisher knowledge affect seahorse conservation status? Animal Conservation 13: 526–533. https://doi.org/10.1111/j.1469-1795.2010.00377.x
  16. Dy DT, Uy FA, Caindec VEC, Perez JLD (2008). Impacts of recreational scuba diving on a marine protected area in central Philippines: a case of the Gilutongan marine sanctuary. The Philippine Scientist 42. https://doi.org/10.3860/psci.v42i0.364
  17. Catibog-Sinha C, Guzman RS (2015). Enabling sustainable marine tourism in island communities: the case of Gilutungan Marine Sanctuary. BIMP-EAGA Journal for Sustainable Tourism Development 4: 10–23. https://doi.org/10.51200/bimpeagajtsd.v4i1.3095
  18. Project Seahorse. MPA implementation. https://projectseahorse.org/establishing-protected-areas/creating-protected-areas/mpa-implementation/
  19. 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
  20. Bacalso RTM, Juario JV, Armada NB (2013). Fishers' choice of alternative management scenarios: a case study in the Danajon Bank, Central Philippines. Ocean & Coastal Management 84: 40–53. UP Cebu. https://doi.org/10.1016/j.ocecoaman.2013.07.008
  21. Tuang-tuang JG, Cesar SA, Montes HR Jr (2021). Scleractinian corals in EDGE and IUCN Red List of Threatened Species in selected areas of Camotes Sea, Central Philippines. International Journal of Biosciences 18(4): 159–163. https://doi.org/10.12692/ijb/18.4.159-163
  22. 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
  23. Kleiber D, Harris L, Vincent ACJ (2018). Gender and marine protected areas: a case study of Danajon Bank, Philippines. Maritime Studies 17: 163–175. https://doi.org/10.1007/s40152-018-0107-7
  24. Samonte GPB, White AT, Tercero MA, Diviva J, Tabara E, Caballes C (2007). Economic valuation of coastal and marine resources: Bohol Marine Triangle, Philippines. Coastal Management 35: 319–338. https://doi.org/10.1080/08920750601169634
  25. Edullantes B, Maglangit FF, Ortiz A, et al. (2021). A benchmark survey of plankton, fish and benthic composition in Poblacion and Kadurong Reefs in Liloan, Cebu, Philippines. Biodiversity Data Journal 9: e72537. UP Cebu. https://doi.org/10.3897/BDJ.9.e72537
  26. Gulayan SJ, Aaron-Amper J, Belleza DFC, Buscato W, Sotto FB (2015). Bohol, Philippines: building partners for coral reef restoration in Panglao Island. BIMP-EAGA Journal for Sustainable Tourism Development 4: 35–41. Bohol Island State University and University of San Carlos. https://doi.org/10.51200/bimpeagajtsd.v4i2.3184
  27. Bahinting SE, Mostrales TPI, Principe A, Licuanan WY (2022). Deployment of artificial habitats alone cannot make up for the degradation of coral reefs. The Philippine Journal of Fisheries 29: 217–223. De La Salle University. https://doi.org/10.31398/tpjf/29.2.2021-0030
  28. Asaeda T, Barnuevo A, Sanjaya K, Fortes MD, Kanesaka Y, Wolanski E (2016). Mangrove plantation over a limestone reef: good for the ecology? Estuarine, Coastal and Shelf Science 173: 57–64. UP Diliman. https://doi.org/10.1016/j.ecss.2016.02.017
  29. Pata PR, Yñiguez AT (2019). Larval connectivity patterns of the North Indo-West Pacific coral reefs. PLoS ONE 14: e0219913. UP Diliman (Marine Science Institute). https://doi.org/10.1371/journal.pone.0219913

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.

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