TropicalCoast 4th new indd

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July 2008

Box 1. Fish Larvae Distribution and Dispersal Simulation 

Applied in the Sulu Sea (Campos, et al., 2007 and 

Villanoy, et al., 2007).

Most shallow water fi sh species produce eggs and larvae that drift for extended 

periods (e.g., 15-30 days) high above the sea bottom (“pelagic”). These early 

life stages may be retained by local circulation but they may also be carried 

by ocean currents far away from their natal reef. The extent of dispersal or 

retention determines the relative degree of importance of far away sub-

populations to recruitment of new generations.  

The University of the Philippines Visayas (UPV) (Campos, et al., 2007) together 

with the University of the Philippines Marine Science Institute (UPMSI) (Villanoy, 

et al., 2007) surveyed and mapped the distribution of fi sh eggs and larvae (or 

ichthyoplankton) and modeled their dispersal by the seasonal currents.  The 

computer modeling included options to assume: (a) some swimming ability 

by the larvae (at 0.2 m/s); (b) ability to settle after at least 75 percent of pelagic 

larval duration; and (c) larval ability to detect a suitable habitat such as a reef 

(from a distance of 18 km).  However, larval mortality, which is considerable, was 

not factored into the model.

Major fi sh spawning periods are  during summer (April to May) and the 

transition to the northeast monsoon (October to November).  Results of 

modeling indicate that fi sh spawned in Western Visayas (Antique and Negros) 

during summer can settle as larvae in the Cagayan Ridge.  Meanwhile, fi sh 

spawned in the Cagayan Ridge during summer can settle as larvae in the east 

coast of Palawan (including Balabac).  Fish spawned in the Cuyo Shelf (north of 

the Palawan mainland) also settle southwards along the east coast of Palawan 

during the monsoon transition period.  Thus, the eastern coast of Palawan 

receives fi sh larvae during both major spawning seasons.  

Map showing the distribution of fi sh larvae densities in Central Sulu 

Sea in April 2007. Arrows denote ocean currents. 

Projected dispersal of egg, pre-fl exion  and 

fl exion larval stages origination from (A) 

Cagayancillo, (B) Cawili-Arena Shoals, and 

(C) Tubbataha up to settlement stage (post 

larvae at 15 days) in Sulu Sea during the 

Summer (April).

Egg

Pre-Flexion

Flexion

Settlement 

Probability

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41

Tropical Coasts

Providing Inputs in the 

Design of  MPA Networks 

The results from various MPA-related 

projects and research studies funded 

under the Sulu-Sulawesi Seascape 

Phase 1 (2005 to 2008) were integrated 

to propose an MPA network design 

based on ecological criteria for each of 

the corridors. Information from local 

perceptions and scientifi c studies (see 

boxed  articles) were combined using 

Geographic Information System (GIS) 

map-based analyses to elucidate more 

objectively key state and pressure/

threat indicators that are useful to guide 

decision-makers and local managers 

in MPA site selection and network 

establishment. (Editor’s note: See Figures 

1-5 in “Partnerships at Work in the Seas 

of Sulu and Sulawesi”, page 12 for related 

information.)

The integration of studies aimed to 

derive key ecological and threat criteria 

relevant for MPA site selection, and 

provide site-specifi c recommendations 

on the appropriate design (i.e., location, 

size and confi guration) of networks 

of MPAs in the three marine corridors 

within the Sulu-Sulawesi Seascape. 

Spatially defi ned grids (2.5 - 5.0 km

2

) 

and a point-scoring system were used to 

transform discrete data into GIS maps. 

Key ecological criteria used in the 

analyses were: 

1.  Extent of marine habitats based on 

remote sensing information; 

2.  Condition of marine habitats – 

corals, reef fi shes, seagrasses, 

mangroves; 

3.  Replenishment potential 

(derived from fi sh egg and larvae 

distributions);  and 

4.  Presence and/or absence of 

threatened seabirds, sea turtles and 

mammals. 

Figure 1.  Possible MPA network design for Verde Island Passage with ecological (habitat and species-based) and 

threat criteria considered.

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42

July 2008

Threat criteria were based on the 

presence and/or absence of human-

induced stressors/impacts to species 

and habitats such as illegal and 

destructive fi shing, mangrove cutting, 

etc. Threats and degree of impacts based 

on stakeholder perceptions during 

consultations and actual fi eld data were 

also considered. 

Within the Verde Island Passage, the 

integrated map shows high priority 

areas for MPA establishment to consist 

of Lubang Islands (Looc and Lubang 

municipalities), the municipalities of 

Calatagan, Lian, Mabini and Lobo, and 

Verde Island (Batangas City) (Figure 

1).  However, combining the ecological 

and threat criteria indicate that most of 

the Calatagan area and specifi c places 

in Lubang, Looc, Batangas City and 

Lobo are places of high ecological and 

threat values. The combined threatened 

species (i.e., cetacean and sea turtles) 

and threat criteria revealed that specifi c 

areas in Balayan Bay and in Calatagan 

are between medium to high priority 

areas. There is good concordance with 

the location of existing no-take MPAs 

in Batangas, but the current total area 

of no-take MPAs in this province is only  

about 6 km

2

 (600 ha). 

For Cagayancillo, the southern (villages 

of Magsaysay to Sta. Cruz) and southwest 

portions (villages of Talaga, Mapio and 

Nusa) of the Cagayancillo reef complex 

and the small islands on the eastern side 

(Bonbon and Manucan Islands) are the 

recommended high priority areas for 

MPA establishment (Figure 2). 

For Balabac Strait, results show that the 

southwest of Pandanan and Bugsok 

Islands and the west-southwest and 

northeast portions of the Balabac 

mainland are the suggested high priority 

areas where new no-take/core zones can 

be established (Figure 3).

The integrated maps were presented 

during multistakeholder convergence 

workshops held separately for 

Figure 2. Possible MPA network design for Cagayancillo with ecological 

(habitat and species-based) and threat criteria considered.

the MBCCs. The maps helped 

decision-makers and stakeholders  

in harmonizing locations for their 

priority marine resource uses, more 

systematically design the locations 

and sizes of a network of MPAs, and 

identify interventions like mangrove 

rehabilitation. In the future, decisions 

and inter-town cooperation could 

be better supported by improved 

understanding of the network of sources 

and sinks of various marine populations.

Lessons and Knowledge 

Gains  

•    Confi rmation of decisions. At 

diff erent spatial scales, results 

clearly show more objectively the 

concordance or non-concordance 

of the recommended sites for MPA 

establishment vis-à-vis the location 

and size of existing ones based 

on habitat extent, replenishment 

potential, conditions, threatened 

species, and threats.

•    Useful tools for decision. The 

map-based presentation of data 

and information from stakeholder 

perceptions and scientifi c studies 

can be useful tools to communicate 

and to convince various parties and 

local governments to be part of 

a network, formally or informally, 

to achieve a common target. For 

example, if the goal of the network 

is to protect at least 20-30 percent 

of the critical habitats, the corridor-

wide MPA network design could be 

used to help municipalities strategize 

towards achieving specifi c goals.  

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