Geographic Location/Coverage. The
Davao Gulf is located in the
southeastern part of the Philippines
(Figure 1), about 984 km south of
Manila. It lies approximately between
6º7’ and 7º4.5’ north latitude and
125º11.5’ east latitude. It is bounded by
Davao City and the four provinces of
Davao del Sur, Davao del Norte,
Compostela Valley and Davao Orienta.
It lies south of the wide flood plains of
Davao del Norte and west of the
adjacent provinces of Bukidnon and
The gulf has an area of 6,600 km2 and a
coastline of approximately 500
km. The average depth of the gulf is 17
m, volume approximately 112x109
m3. The high mountain ranges of
Sarangani Province in the west and
south-west, the mountain ranges of Mt.
Apo (the highest Philippine peak) in the
north and north-west portion of the region, and the mountain ranges of Davao del Norte
and Oriental in the eastern side, surround the gulf. Within the gulf are the islands of
Samal and Talikud.
Soils. The surface soils of land surrounding the Davao Gulf are mostly clay and loam
types that are well-suited for plantation crops (e.g. banana, pomelo, durian, and coconut),
cut flowers and orchids.
The Davao region, which is generally free from typhoons, has a mean rainfall of 180.9
mm/yr that is evenly distributed throughout the year (PAGASA). The mean annual
temperature is 27ºC while mean humidity value is 82%. The prevailing wind direction is
north during the operation of the north-east monsoon from October to May. The south-
west monsoon operates from June to September. The mean speed rate during the two
monsoon seasons is 16 km/hr.
Extent/Size of Coastal Resources. The Davao Gulf has a water area of 10,500 km² and
a total catchment area of 5,132 km² which is derived from the various watersheds of
Sarangani, Davao del Norte, Davao Oriental, Compostela Valley, and Davao City. The
average depth of the Gulf is 17 meters and volume of approximately 112x109 m³ (V.
Dupra and S.V. Smith). Its widest point is approximately 160 km while coastline is
approximately 520 km., reckoned from Calian Point in Davao del Sur to Cape San
Agustin in Davao Oriental (or excluding the coastline from Calian Point to the
Municipality of Sarangani). Within the Gulf are the islands of Samal and Talikud in
Davao del Norte, Kopiat in Davao Oriental and Lunod in Compostela Valley (MSU-
Hydrology. The 33 major rivers
and creeks that drain into the
Davao Gulf make the inner part
of the Gulf estuarine in
character (V. Dupra and S.V.
Smith). The water of the Gulf
is oceanic in nature considering
that the Pacific Equatorial
current flows westward and
northwest as it reaches the
western boundary rim (eastern
part of Mindanao) of the Pacific
Ocean. The water mass is
affected by the tidal force
resulting from the earth’s
rotation on its axis.
Water exchange is mainly tidal with relatively good surface mixing during strong
monsoon winds. The northern portion is generally estuarine in character due to the
massive influx of freshwater from the flood plains especially during the rainy season.
Prevailing Tidal Fluctuations. The Gulf has a unique pattern of water movement.
During flood tide, water mass south of Samal Island flows southwest averaging about
0.26 to 0.42 m/sec. In the northern portion of the island, between Bassa Point and Gill
Point, water mass flows northeast, then southward and swiftly veers east-northeast during
the peak tide current. During a flooding event, the more saline oceanic waters move
through the deeper section of the Gulf pushing the older water mass northward. Tide
waves occurring ahead at the eastern section cause older water to wave towards the area
of low elevation at the western side. Eddies and standing oscillations are present.
Watershed. The Davao Gulf is the final catchment for all runoffs, erosion and effluents
coming from several watersheds in the region whose headwaters come from the mountain
ranges of Sarangani Province in the west and south-west portion of the region, the
mountain ranges of Mount Apo (the Philippines’ highest peak) in the south portion, the
mountain ranges of Davao del Norte in the north and north-west portion, and mountain
ranges of Compostela Valley and Davao Oriental in the eastern side.
Thirty-three tributaries or rivers and creeks drain into the Gulf (Figure 1). These
tributaries make up 12 major watersheds and 8 micro watersheds, as defined by the River
Basin Committee for the Davao Gulf Tributaries (DENR XI).
Davao del Sur Balutakay Watershed
Davao del Norte
Davao River Watershed
Davao Oriental Sumlog Watershed
Figure 1. Twelve major watersheds of the Davao Gulf
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
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.