The Davao Gulf is endowed with major coastal habitats such as mangroves, seagrass, coral reefs and soft-bottom communities that directly and indirectly support fisheries. In recent years, man-made habitats such as artificial reefs were introduced to enhance fish stock.
Mangroves .The estimated mangrove cover of the Gulf differs significantly among studies, probably because of the methods used. Some of these estimates were based on spot satellite maps that need on-ground validation while the others were based on topographic maps using different scales. Of the estimated 2,683 hectares of mangroves based on the 1950 NAMRIA maps, 1,391 hectares had been converted into fishponds and 845 hectares, for other purposes. By 1995, only 295 hectares (11%) had been accounted for (BFAR, 2000). View Table 1: Distribution and approximate mangrove area for each municipality in the Davao Gulf.
An inventory of mangrove area using composable data at various periods shows the distribution and approximate mangrove area at Davao Gulf.
A study by the University of the Philippines in the Visayas Foundation, Inc. (2000) listed 20 species of mangroves in the Gulf (View Table 2). Fourteen of them were classified as true mangrove species with the most common belonging to genera Rhizopora, Sonneratia and Avicennia. Brgy Cagangohan of Panabo (Davao del Norte) and Lunod Island of Mabini (Compostela Valley) have the most number of mangrove species. Trees reaching 20 meters high still exist in barangays Bato and Tuban in Sta. Cruz, Davao del Sur.
Of the 65 known species of mangroves worldwide (UNDP/UNESCO, 1986), 50 species belonging to 26 families can be found in the Philippines (Calumpong, 1997). In the Gulf, 27 true mangroves and 23 mangrove associates are grown in the first on-site mangrove laboratory in Southern Philippines, the San Isidro Mangrovetum in the Island Garden City of Samal (IGaCos). With the assistance of the Coastal Environmentalist Conservation of Samal Island, Inc. (CECSI), a federation of five people’s organizations in IGaCos, the DENR in Region XI plans to propagate all 47 true mangrove species.
In year 2004, seaweed projects amounting to P550,000.00 were awarded to 11 registered people’s organizations (PO) in the Gulf. These projects where each PO got P50,000.00 through the Presidential Commitment and National Security Plan Fund benefited 720 people, excluding those that got funding assistance from the Fisheries Resource Management Project (FRMP) of the Department of Agriculture-Bureau of Ffisheries and Aquatic Resources in Region XI (DA-BFAR XI).
Seagrasses. There were nine species of seagrasses that were observed in 12 sites around the Davao Gulf excluding Davao Oriental (UPVFI, 2000). The seagrass species are Cymodocea rotundata, C. serrudata, Halodule pinifolia, H. uninervis, Syringodium isoetifolium, Halophila minor, H. ovalis, Thalassia hemprichii and Enhalus acoroides. Species diversity varied considerably between areas.
Seaweeds.Twelve species of seaweeds, the most common of which were Genus Padina and Enteropmorpha, were also counted. (View Table 3: Seaweed species observed in 12 sampling stations in the Davao Gulf )
Corals. Manta tow surveys covering 33.8 kilometers of reefs in the Gulf showed that only one-fourth of the coral cover was live (View Table 4). Of the 19 areas surveyed, only the corals in Tubalan were in very good condition. Areas with poor values of 10% and below were found in Agdao, Malita and Valez (Toril) in Davao City. Thirty-four genera of hard corals and three genera of soft corals were identified, suggesting high species diversity (View Table 5).
As shown in Table 6, the total length of reef formation was estimated to be around 412.1 km. (UPVFI, 2000). These were mostly reefs surrounding the islands and shoals of Samal in Davao del Norte (127.4 km.) and the fringing reefs of the mainland of Davao Oriental (114 km.) and Davao del Sur (102.7 km.). Live coral cover was noted to be decreasing over a period of five years (MSU, 1995 and UPVFI, 2000).
Fisheries. The Davao Gulf is an important spawning and nursery for tuna, according to a study commissioned by the Fishery Resources Management Bureau of the Bureau of Fisheries and Aquatic Resources (BFAR). (See Economic Indicators for details.)
Marine Turtles.The turtle population worldwide is declining and listed as endangered by the CITES. Of the seven species of marine turtles still existing, five are found in the Philippines. All of these are present in the Davao Gulf.
Since 1998, the DENR XI has tagged and released at least 59 turtles. Despite local stories of nesting grounds around the Gulf, only the local government of Davao City has created a Pawikan Task Force to spearhead the management and conservation of marine turtles in the area in response to the recent discovery of turtle nests in Punta Dumalag. The municipal government of Pantukan in Compostela Valley also passed a resolution providing incentives to fisherfolks who can capture and release sea turtles.
Dugongs.Dugongs (Dugong dugon) or sea cows, which feed on seagrass, have been sighted near the shores of Davao Gulf particularly in the coasts of Malalag, Malita and Don Marcelino in Davao del Sur; IGACOS in Davao del Norte, and Gov. Generoso in Davao Oriental. These timid creatures are likewise endangered under CITES. Dwindling seagrass habitats and other anthropogenic causes contribute to the continued decline of the dugong population.
Dolphins and Whales.The Davao Gulf serves as a feeding ground for various species of highly migratory cetaceans such as dolphins and whales. The survey in March 2004 by a composite team from the DA-BFAR, the Save Davao Gulf Foundation, Inc. (SDGFI), and the WWF- Philippines, confirmed the presence of 11 cetaceans in the Gulf making it the second top cetacean diversity sight in the Philippines, next to Babuyan Islands that has 13. Of the 11 cetaceans discovered, seven species are whales while four species are dolphins. Sightings, which have been frequent based on persistent reports by fishermen to include cases of unfortunate beaching, are estimated at 77 (DA-BFAR, 2004). These were around the southern portion of Ligid Island, Samal Island and south of Barangay Matina in Davao City. It should be noted, however, that eight of the 11 species are listed in Convention on the International Trade of Endangered Species (CITES) as threatened by extinction unless protected and conserved. The pygmy6 sperm whale, which was the last to be discovered in the Gulf, is classified under CITES as species that is “not necessarily threatened with extinction, but in which trade must be controlled in order to avoid utilization that is incompatible with their survival”.
Birds. The Davao Gulf is an important feeding area for egrets and ducks, and an important staging for migratory shorebirds. In May 1987, Howes (1987) visited four sites in the Gulf and observed small numbers of Egretta eulophates, E. garzetta, E. intermedia, 445 Dendrocygna arcuata, 26 Anas luzonica and 675 shorebirds of 17 species including Numenius madagascariensis. Migratory of Malalag in Davao del Sur and Carmen in Davao del Norte.
DAVAO GULF NEWS