40
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
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.
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.