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Davao City, Philippines

Davao Gulf: Sustaining reef fish diversity amid adversity

March 19, 2020 - Thursday 6:03 PM by MDM

Article Banner Image DAVAO GULF CORALS. Corals provide marine organisms food and shelter. CLETO L. NA?OLA JR.

The Philippines is known to be a mega-diverse country in terms of marine fauna, which accounts for more than 2,500 species of reef fishes owing to its unique archipelagic setting. The country is divided into six marine biogeographic regions that significantly influence the abundance and diversity of marine organisms.

In 2009, the Department of Environment and Natural Resources (DENR) identified 123 Marine Key Biodiversity Areas (MKBAs) in the Philippines. MKBAs are areas known to have diverse marine flora and fauna—a great source of seafood such as fish, molluscs, and crustaceans for the people.

Davao Gulf is listed among the country’s MKBAs.

A SCHOOL IN VANISHING ISLANDS. A school of surgeonfish is seen swimming in the waters
of Vanishing Island, Island Garden City of Samal (IGACOS), Davao del Norte. CLETO L. NA?OLA JR. 

Protecting the food source

The amended Fisheries Code of 1998, or the R.A. 10654, promotes the protection of marine habitats in order to secure food production, directly or indirectly, through the “spillover effect” or through the “source and sink” of larval propagules, particularly for reef fishes.

On the first hand, source and sink in ecology means an area where a certain species lives and dies. On the other hand, the spillover effect happens when there is overcrowding in a protected area—causing reef fishes to move or explore in adjacent reefs. Safeguarding these Marine Protected Areas (MPAs) allows reproduction of reef fishes and in effect, fish production is sustained.

MPAs consist of mangrove, sea grass, and coral reef ecosystems. These habitats ensure that there will always be nursery grounds for marine fauna, particularly for reef-associated fishes such as herbivores (parrotfishes and surgeonfishes), top carnivores (groupers and sweetlips), and other large pelagics, (tuna, barracudas, and jacks).

This food chain then encourages reef integrity to be resilient—it can withstand certain degrees of disturbance, given that these disturbances do not inundate the marine habitats. One example of a major disturbance that can totally destroy the coral reefs is prolonged siltation brought about by man-made activities.

SCENIC SPOT. Aside from marine animals, humans can also enjoy the beauty of this
underwater haven through diving. CLETO L. NA?OLA JR. 

MPAs in Davao Gulf

Recently, a regionalization called the Fisheries Management Areas (FMAs) was established by the Bureau of Fisheries and Aquatic Resources (BFAR).These regions are applying the Ecosystem Approach for Fisheries Management (EAFM) where both the ecological and human well-being are met towards sustainable fisheries. Using either of these established “regionalizations”, Davao Gulf falls within one major group—the Celebes Sea Biogeographic Region or the FMA 2, which suggests that Davao Gulf is indeed a unique region.

Davao Gulf has a total of around 50 MPAs. In Samal Island alone, there is a total of around 20 MPAs.

Based on a scientific report, the Celebes Sea hosts an estimated number of 564 reef fish species. 73 percent of the recorded reef fish composition in the Celebes Sea can be found in the Davao Gulf. Davao Gulf comprises only a small portion of the entire Celebes Sea Biogeographic Region yet more than half of reef fish species is found in this embayment.

In the past, reef fishes abound in almost all coastal municipalities, simply because there used to be an abundant supply anytime. Knowing that there has been a decline in fisheries production, the SMARTSeas Ph Project and local government units (LGUs) are working together to ensure food security through the establishment of MPAs. In turn, these local efforts should not deprive the small scale fishers in coastal communities of their livelihood.

So, what does the high diversity of reef fishes mean in a marine environment? For as long as the reef fish composition in a particular area remains as it is, these species will contribute in protecting the reefs hence, making it resilient. But major disturbances leading to the direct destruction of their habitats, the coral reefs, is not within their control. Excessive sediment discharge that impacts coral reefs is tantamount to human settlements being affected and destroyed by lahar. When these reefs become totally destroyed, only time will tell if it still can recover or worse, it will shift to a different environment. If we still want to have many fishes in the sea, then let us act in protecting our reefs for our benefit and the generations to come.

Cleto L. Nañola, Jr. is a marine biologist with a Ph.D. degree in Marine Science from the Marine Science Institute, University of the Philippines Diliman, Quezon City. He is currently an Associate Professor at the Department of Biological Sciences and Environmental Studies of the University of the Philippines Mindanao in Mintal, Davao City and the Laboratory Head of Coral Reef Resiliency and Ecology Studies Laboratory. His expertise is on the biology, ecology, and biogeography of reef fishes.