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Escalante Biodiversity and Ecosystem Report 2020 - Sustainable Priorities and Sustenance


Abstract and Figures

In 2018, the government of Escalante city, Philippines, sought to improve the sustainability of marine resource utilisation within Escalante waters as part of a larger overhaul of sustainable resource use within its borders. As part of this effort, Conservation Diver was approached to provide an ecological assessment of species richness and ecosystem health within Escalante, with a particular focus on assessing the suitability of the Marine Protected Area (MPA) within Escalante waters, 15 years after its initial designation. Surveys were conducted at multiple locations throughout the Escalante coastline to provide an initial inventory of species found, with further ecological assessments being carried out in coral reefs at various sites. A total of 714 species were recorded in Escalante waters during the survey period. Coral reefs surveyed were found to be highly variable in their community structure and coral cover, and were found to support generally low abundances of reef-associated fish and invertebrates, particularly of those groups which were known to be of commercial value. Surveys of the fish market yielded remarkably high levels of legal and illegal catch from within reef areas. Surveys within the currently designated MPA revealed very little coral cover and drastically lower biodiversity or commercially valuable marine resources of virtually any kind when compared to most surveyed locations within Escalante waters. We therefore propose alternative zonation strategies and improvements to the sustainability of resource use at Escalante and provide an initial framework for further assessment and development of sustainability within Escalante waters.
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Escalante Biodiversity and
Ecosystem Report – 2020
Escalante Biodiversity and Ecosystem Report – 2020
Sustainable Priorities and Sustenance
Rahul Mehrotra, Coline Monchanin, Maggie Seida, Ellen G. Funesto, Harrison Carmody and Sarocha Pakeenuya
Preliminary Ecological Assessment Project
Supported by Escalante City, Conservation Diver, University of the Philippines Cebu and
Love Wildlife Foundation.
This paper represents the work by the authors and all opinions expressed are those of the authors alone.
Copyright of all material included in this work is retained by the authors including all figures, tables and
photographs, which were taken by the authors personally. All photographs were taken at Escalante
during the course of the data collection. Photographs for all species listed within this report and its
supplementary list are held at the governing body of Escalante City, and copyright for all photographs
is retained by the authors of the present report. This report is aimed at people with varying degrees of
scientific understanding and background, from interested non-academics and representatives of the local
governing body, to active biologists and marine biologists around the world.
In 2018, the government of Escalante city sought to improve the sustainability of marine resource
utilisation within Escalante waters as part of a larger overhaul of sustainable resource use within its
borders. As part of this effort, Conservation Diver was approached to provide an ecological assessment
of species richness and ecosystem health within Escalante, with a particular focus on assessing the
suitability of the Marine Protected Area (MPA) within Escalante waters, 15 years after its initial
designation. Surveys were conducted at multiple locations throughout the Escalante coastline to provide
an initial inventory of species found, with further ecological assessments being carried out in coral reefs
at various sites. A total of 714 species were recorded in Escalante waters during the survey period. Coral
reefs surveyed were found to be highly variable in their community structure and coral cover, and were
found to support generally low abundances of reef-associated fish and invertebrates, particularly of those
groups which were known to be of commercial value. Surveys of the fish market yielded remarkably
high levels of legal and illegal catch from within reef areas. Surveys within the currently designated
MPA revealed very little coral cover and drastically lower biodiversity or commercially valuable marine
resources of virtually any kind when compared to most surveyed locations within Escalante waters. We
therefore propose alternative zonation strategies and improvements to the sustainability of resource use
at Escalante and provide an initial framework for further assessment and development of sustainability
within Escalante waters.
Recommended Citation: Mehrotra R., Monchanin C., Seida M., Funesto E.G., Carmody H. and
Pakeenuya S. (2020). Escalante Biodiversity and Ecosystem Report - " Sustainable Priorities and
Sustenance". Conservation Diver. 48pp.
This project would not have been possible without the initiatives of Eddie M. Montero, City Mayor of
Escalante, Vermont Khan Juhavib, head of Community Environment and Natural Resources Office
(CENRO) Escalante, and Bobby Valencia Jr. Throughout the fieldwork efforts, support and remarkable
assistance was provided by the Escalante City Officials. In particular, members of the CENRO team
including Rolyn T. Cabus, Elean M. Buenavista, Randy S. Mahusay, Edmund M. Pation and Joevic
Peñas. We would also like to thank members of the CENRO Fishery Law Enforcement Team including
Ronelo B. Morijon, John Miguel D. Rojo, Rodel Doromal, Jesus Siasico, Warlie Clarin, Julito Portado,
Jujie Montecalbo, Badelon Tupas, Joemarie Gamao and Julio Gamao. Assistance in the report writing
process was provided by Kaitlyn Harris and Serena Harris. We would also like to thank all the reviewers
whose comments and suggestions improved the quality of the final report. We would like to thank Chad
M. Scott for facilitating research efforts within Conservation Diver. Equipment and assistance was
provided by the Department of Biology and Environmental Science, College of Science at the University
of the Philippines Cebu, and by Love Wildlife Foundation, Thailand. This project was funded and
supported by Escalante city in partnership with Conservation Diver (Registered US Charity
1 – Introduction
- Objectives
2 – Methodology
3 – Results
- Biodiversity Assessment
- Ecological Assessment
- Fish Market Assessment
4 – Discussion
- Ecosystem Health
- Zonation
- Steps towards Sustainability
5 – Conclusions
1 - Introduction
There is little doubt today that global biodiversity and ecosystem health is suffering under the pressure
of natural and human-induced threats. Inaction or underwhelming responses to global challenges,
combined with a lack of information on many crucial variables (i.e. the present-day status of most
known species) has led to dire predictions for global economic, ecological and environmental health
(Braat et al., 2008; Ten Brink et al., 2010; Oliver 2016). Arguably, the most well-known and
comprehensive databases of species status and threats is the International Union for the Conservation of
Nature Red List, which has assessed the status of over 112,000 species at the time of writing (IUCN
2020). Due to biases and challenges in the assessment protocols of the Red List (Hayward et al., 2015;
Collen et al., 2016; Cowie et al., 2017), however, these efforts remain largely ineffective at monitoring
overall biodiversity loss as well as local and even complete extinctions of the vast majority of the
approximately 2 million known fauna (Cardoso et al., 2012; Cowie et al., 2017). It is therefore apparent
that greater efforts must be made in mapping and monitoring biodiversity globally, particularly in
ecologically rich and unique areas, as well as those areas that have been overlooked. When combined,
localised assessments of such places and of broader taxonomic groups (i.e. those outside of Chordata)
can provide a more comprehensive analysis of changes in biodiversity and ecosystem health, while
contributing to the understanding of the issue over larger spatial scales. More so, knowledge of an
ecosystem, when managed appropriately, can lead to economic gain and sustainability in the
surrounding community (Samonte et al., 2016; Spalding et al., 2017).
The Philippines is located within the ‘Coral Triangle’, a region representing some of the greatest marine
biodiversity on the planet (Veron et al., 2009; White et al., 2014). The exceptionally high biodiversity
within the Philippines, while objectively well accepted (i.e. Carpenter and Springer 2005; Gosliner et al.,
2018), remains largely understudied (Scheffers et al., 2012; Gosliner et al., 2018). The most recent and
extensive assessment of coral reefs throughout the Philippines has shown that sizeable areas of the
Philippines reefs and coastal habitats remain to be surveyed and assessed (Licuanan et al., 2017).
Additionally, the marine protection initiatives in place within the country have been shown to be highly
variable in their enforcement and resulting efficacy, with many areas shown to be lacking in protection.
Marine Protected Areas (MPAs) are typically coastal or offshore areas theoretically designated to be
subjected to higher than local-average levels of protection and enforcement so as to promote recovery
and/or growth of marine resources. Within the coral triangle, MPAs are typically designed with at least
one of two main factors in mind: a) economic growth or sustainability by promoting fisheries resources
or tourism, and b) ecological protection of threatened marine organisms or habitats, often combined with
regulated tourism (Abesamis et al., 2006; White et al., 2014).
Numerous reviews and case studies have been conducted about MPAs within the Philippines, which
hosts some of the highest numbers of MPAs in the region, however, the success of many has been
debatable for years (see White and Cruz-Trinidad 1998; Aliño et al., 2002; 2004; Beger et al., 2004;
Samoilys et al., 2007; White et al., 2002; 2014; Espectato et al., 2017; Sato et al., 2017). A lack of
comprehensive and cohesive stakeholder involvement and, in particular, insufficient or inefficient
enforcement practices leave many MPAs effective on paper only, hence the term ‘paper parks’ or
‘paper-MPAs’ (Ross et al., 2002; Launio et al., 2010; Horigue et al., 2012). While consensus on the
definition of a ‘MPA’ or site-specific strategies for optimal marine resource protection are yet to be
reached, numerous elements and recommendations are generally agreed upon. These include a) that
ineffective enforcement is a weak link, b) a lack of stakeholder and/or political will, results in sub-par
zonation and c) that networks and corridors of protected areas are vital instead of isolated MPAs.
Various attempts have been made to provide an economic valuation for the variety of ecosystems in
South-East Asia with the more comprehensive reviews (i.e. Conservation International 2008) comparing
the Philippines to other regions under some standardised criteria. As values of coral reefs in the
Philippines have been calculated using different methodologies, there is variability in the estimations,
with total annual benefits of these ecosystems ranging from approximately USD 450 million to USD 1.4
billion (~ USD 266,000 – 827,500 per km2) (White et al., 2000a; White et al., 2000b; Burke et al., 2002;
Samonte-Tan and Armedilla 2004; Samonte-Tan et al., 2007). These are often based on extrapolations
from localised assessments and vary on inclusion and exclusion of certain passive benefits such as
erosion protection and aesthetic value. Among the leading contributors to the valuation of the
Philippines coral reefs is that of tourism which has played an increasingly dominant role in recent
decades (see Samonte et al., 2016; Spalding et al., 2017 and others). Similarly, valuations of mangrove
and seagrass habitats in the Philippines have highlighted the importance of tourism in such areas (White
et al., 2000a; Samonte-Tan et al., 2007; Conservation International 2008). Indeed, tourism related to
understudied and ill-defined subtidal soft sediment habitats (or ‘muck’ habitats) has been shown to
support a USD 150 million SCUBA diving industry, to which the Philippines is a large contributor (De
Brauwer et al., 2017). Recent assessments by the Philippines Statistics Authority (PSA 2018) suggests
the value of coastal and marine tourism nationwide (including all ecosystems) has increased from USD
2.461 billion in 2012, peaking at USD 3.055 billion in 2015, and then USD 2.992 billion in 2016.
With regards to fisheries production associated with coral reefs in the Philippines, precise estimates are
limited by a lack of standardisation and accepted definitions. Overall, some attempted assessments have
been made in highly localised areas comparing biodiversity and abundance of catch between reef-
associated and non reef-associated species (i.e. Galenzoga and Quiñones 2014; Mehrotra et al., 2017).
The role of overfishing and habitat loss in shifting fisheries management in the Philippines has been
documented for many years, alongside its position as a dominant region for global fisheries production
(Green et al., 2003; FAO, 2005). The changes and impacts of such exploitation are also the case for the
central Visayas region (Green et al., 2004). For context, over-exploitation and a changing climate have
contributed to changes and challenges in global fisheries and have resulted in losses amounting to
between 51 and 83 billion USD annually (Cashion et al., 2018). In particular, global tropical fisheries
have faced many challenges with many areas, including the Philippines, continuing to employ illegal and
destructive fishing practices, with declines in coral coverage associated with parallel declines in fish
biodiversity (Jones et al., 2004).
In recent years, members of Conservation Diver have consulted upon the zonation of MPAs and
assessments of biodiversity, health, and threats at Toboso, North-East Negros Occidental (Mehrotra et
al., 2016; 2017). Escalante is within the Tañon strait and thus management efforts are a part of the
Tañon Strait Protected Seascape (TSPS), which remains among the largest bodies of water in the
Philippines with a mandate for protection. Unlike other formally designated MPAs elsewhere in the
Philippines, the TSPS provides a set of common guidelines and requirements for protection for each of
its over 40 bordering municipalities and jurisdictions to then individually delineate and manage (TSPS-
GMP 2015). The Tañon Strait and other areas in the Visayas have undergone some assessments
regarding the efficacy of MPAs, (i.e. Pollnac et al., 2001; Christie et al., 2009) however, few intensive
assessments have been carried out regarding total faunal diversity and high spatial resolution
assessments of reef habitats.
Aims and Premise
Escalante is currently classified as a 4th income class city (PSA 2019) in the North-East of Negros
Occidental. It hosts an estimated population of 94,000 people, with the main industry being agricultural
production of sugar cane, and to a smaller extent, rice and corn (Guadalquiver and Nicavera, 2019).
Escalante has 19 Barangays (a Barangay is the smallest administrative division in the Philippines), seven
of which are coastal (Amante, 2019). Escalante currently hosts an MPA of over 1,300 hectares,
established five years after the creation of the TSPS in 1998 (Escalante city ordinance 156, October
2003), which was later developed and incorporated into the present zonation (Fig 1, Appendix I). As part
of efforts by the governing body to update and improve the sustainable use of marine resources at
Escalante, members of Conservation Diver were approached to assist in this aim. Specifically,
consultation was sought regarding a) classification and diversity of faunal marine resources, b)
assessment of status and long-term prognosis of those resources, and c) assessment on suitability of the
present MPA currently delineated within Escalante. Here we present the targeted objectives, protocols
and findings of this assessment for primary use by the Escalante city to improve sustainable use of the
natural marine resources at Escalante.
Figure 1 – Partial zonation map of Escalante highlighting areas currently allocated to marine protection
(MPA), mangrove restoration, mariculture, and tourism, modified from complete zonation information
provided by Escalante city.
Objectives Summary:
1) Conduct a preliminary inventory of marine flora and fauna in the coastal ecosystems of Escalante.
2) Evaluate the current health of and threats to the coastal ecosystems of Escalante, with a particular
focus on coral reefs
3) Investigate the status of the fishery at Escalante
3) Assess the state and suitability of the designated MPA at Escalante.
4) Assess the effectiveness of the Coastal Patrol/Bantay Dagat in preventing illegal and unsustainable
practices at Escalante
5) Provide recommendations to improve the ecological and economic value of the coastal habitats of
Escalante and propose solutions to threats to the longevity and sustainable use of these coastal areas.
2 - Methodology
Field surveys were conducted in the form of transect surveys and roving surveys and were carried out
between the 2nd and 25th of March 2018. Roving surveys were implemented at a variety of habitat types,
both nearshore and offshore, and were completed via both snorkelling and SCUBA diving at depths
ranging from 0.5m to 25m. A focus was applied to coral reef and soft sediment habitats so as to
maximise data from both high biodiversity and highly cryptic areas. Surveys were also carried out at
some nearshore and offshore mangroves, and seagrass habitats. Photographic documentation was carried
out using Olympus TG4 and TG5 cameras and housings. Where possible, the morphology of species
was investigated, and size approximated in-situ to support photographic species distinctions. Precise
GPS coordinates for all sites surveyed were collected using a Garmin eTrex® 20x GPS receiver (Fig. 2,
Table 1). Surveys were carried out at both day and night-time and included sites both within and outside
the currently designated MPA.
Table 1 Coordinates for surveyed sites for overall ecological assessment and biodiversity inventory
efforts only.
Ecological Assessment Site
Biodiversity Assessment Site
10° 54'27.35"N - 123°33'49.79"E
10° 53'43.30"N - 123°33'58.58"E
10° 53'33.45"N - 123°34'16.41"E
10° 53'33.83"N - 123°34'10.32"E
10°52'28.05"N - 123°32'11.69"E
10° 52'22.53"N - 123°32'59.29"E
10° 50'34.54"N - 123°33'20.79"E
10° 53'39.40"N - 123°34'21.76"E
10° 53'0.75"N - 123°33'30.17"E
10° 51'59.46"N - 123°33'58.53"E
10° 51'10.17"N - 123°33'37.31"E
10° 49'42.81"N - 123°35'12.72"E
10° 50'45.16"N - 123°34'04.87"E
10° 52'28.11"N - 123°34'32.98"E
10° 52'12.69"N - 123°34'34.53"E
10° 45'24.91"N - 123°33'02.98"E
10° 51'47.67"N - 123°34'19.32"E
10° 49'43.33"N - 123°34'15.04"E
10° 48'26.52"N - 123°33'57.51"E
Figure 2 – Map of surveyed sites. Labelled sites correspond to those subject to ecological assessment in
addition to biodiversity inventories, unlabelled sites corresponding to sites surveyed for biodiversity
monitoring only.
As part of data collection efforts, focused night-time surveys were carried out on the coral reef for seven
days starting on the night of the full moon on the 2nd of March. With the aim of investigating spawning
patterns among the scleractinian corals, these surveys were conducted in addition to day-time surveys to
maximise the observational period for incidental spawning events. During night-time surveys, large and
healthy coral colonies were closely observed periodically between sunset and approximately 10pm.
Surveys alternated between nearshore and offshore sites due to differences in coral community structure
between these (see Results).
Transect surveys were carried out at multiple coral reef areas in both nearshore and offshore sites (Fig
2). All transect surveys followed the Ecological Monitoring Program protocol by Conservation Diver
(Scott 2012) and, where possible, were carried out at two depths. Shallow transects were carried at reef
areas between 2-4m and deep transects were carried out between 6-8m. Invertebrate indicator species
largely overlapped with those carried out at Toboso (Mehrotra et al., 2016; 2017), including Tridacninae
and Holothuridae species, with an added focus on those species observed to be of high commercial value
to the local fishing community (Lambis spp., and Cypraeidae spp.). Additionally, data was collected on
the abundances of the corallimorph Paracorynactis hoplites due to its well documented capacity as an
opportunistic predator of numerous invertebrate taxa (Bos et al., 2011). Data could not be collected on
several other commercially important bivalve and gastropod species (i.e. Volutidae spp.) due to these
animals neither being active nor visible in the surveyed reefs during daytime. Vertebrate indicator
species followed those in the aforementioned earlier studies from Toboso. These included the
Acanthuridae (Surgeonfish), Chaetodontidae (Butterflyfish), Epinephelinae (Groupers), Lutjanidae
(Snappers), Pomacanthidae (Angelfish) and Scaridae (Parrotfish), with data being further subdivided
arbitrarily into larger individuals (>20cm) and those approximately 20cm or smaller. Data was also
collected on various other groups such as specific Pomacentridae and Labridae but these were not
included in the present analysis. As with earlier studies, vertebrate transects were calculated per 100m3
(5m width x 1m depth x 20m length).
Data was collected on the diversity and abundance of illegal fishing catch in Escalante. This was
collected by joining the local sea patrol (Bantay Dagat, henceforth ‘BD’) during standard patrols as well
as targeted excursions upon notification of illegal fishing activity. Surveys were also collected in the fish
markets of Escalante in an attempt to assess the diversity and abundance of catch from local waters.
Surveys lasted approximately 2 hours each and were carried out at least once a day for 15 days during
the total 23-day survey period. Key variables included the approximate price of each fish/mix of fish
being sold (in PHP) and approximate mass (kg) of fish being landed and sold. It should be noted that
previous surveys from the region have shown that some of the catch from Escalante waters are sold
elsewhere, often by fisherfolk from surrounding regions.
Fish market surveys allowed for a comparison of reef fish and non-reef fish sold for consumption at
Escalante. While most species surveyed occupy distinct ecological niches and the categorisation of
‘reef’ versus ‘non-reef’ does not account for species-specific or indeed habitat-specific variability
amongst others, species were generalised as one category or another. This was done by estimating the
proportion of adult life a given species was known to spend within or in direct vicinity of coral reef
areas. This was assessed based on relevant literature as well as in-situ observations conducted. Non-reef
species were largely those that were found to inhabit open water or offshore benthos (such as the
Menidae, Rhinobatidae, Scombridae, etc.). Benthic associated species that may be found at a variety of
habitat types (such as those of the Mullidae, Tetraodontidae etc.) were not included as ‘reef’ so as to
maintain conservative estimates for reef-specific species (such as many species of Chaetodontidae,
Pomacentridae, etc.).
Figure 3 Data is taken along transect lines for ecological assessments.
3 - Results
3.1 - Biodiversity Assessment
An estimated 4.5km2 of the subtidal area was surveyed, including 1.5km of transect surveys along coral
reef habitats in Escalante waters. Throughout the total in-situ and ex-situ (fish market and BD patrols)
surveys, a total of 714 species were recorded (see supplement). Given that the prime focus of the
biodiversity assessment was documentation of faunal taxa, little emphasis was given to biodiversity of
algal and seagrass species which accounted for only 11 species, with the remaining 703 being marine
fauna. Additionally, mangrove diversity was not included as comprehensive documentation on the
diversity found is held at the local government. The greatest diversity of species were Cnidarians,
followed by Chordates and Molluscs, all of which made up 76% of the total diversity presently recorded.
Surveys from within the present MPA yielded 12% of the total diversity found in Escalante, with most
species being recorded from multiple sites. An overview of taxa as divided by phylum is provided
Among the most diverse taxa that were identifiable based on photographic and detailed morphological
data, the vertebrate diversity in the area was 194 species. Unsurprisingly, this diversity was dominated
by fish with only three species of marine reptiles, all snakes (Acrochordus granulatus, Emydocephalus
annulatus and Laticauda colubrina) being recorded. While sea turtles are known from the region, none
were recorded during the survey period. Though marine associated birds also make up an important part
of the coastal ecology, these were not surveyed. Of the 191 fish species, 70 were documented
exclusively ex-situ, primarily from fish market surveys (see supplementary data). For each, estimated
location of catch (within or outside of Escalante) was verified in interviews with vendors. Only 22
chordate species were recorded from within the currently designated MPA. The most diverse families
recorded were the Pomacentridae (21 species), Nemipteridae and Labridae (14 species each).
Figure 4Pomacentridae, Amphiprion polymnus.
Cnidarians were found to be the most
diverse group in Escalante waters with
227 species being recorded. The
majority of these species were
scleractinian corals comprising 143
species, followed by octocorals at 33
species and actiniarians at 20 species.
The high scleractinian diversity is an
incredibly promising feature of
Escalante waters (see Discussion) and
is reflective of the high diversity
associated with the Philippines. Most
of these reef building corals were
successfully identified to tentative
species level based on close
morphological inspection, however,
most octocoral taxa were kept broader
due to the inability to sample and
assess sclerite morphology. Only 28 of
the total 227 species were recorded
within the current MPA and all were
also recorded at other sites. A total of
217 anthozoan species were identified
with non-anthozoan taxa including
seven hydrozoan species, two
scyphozoans, and a single cubozoan. It
is likely that further surveys will dramatically increase the known diversity of these groups.
The majority of documented crustacean diversity were decapod taxa which made up 36 of the total 40
species recorded at Escalante, with a single species of stomatopod and three distinct but unidentified
species of Cirripedia. Eight species were found within the MPA site not including the three species of
Penaeidae found in Escalante waters with known commercial value in both local and regional fisheries.
One species found within the MPA and throughout numerous sites was the crab Portunus (Portunus)
pelagicus which is of widespread commercial value. It is strongly believed that more extensive surveys
will likely yield rapid increases in the documented diversity of Cirripedia, Decapoda, and Stomatopoda
Of similar scale to crustacean diversity was that of the echinoderms, of which 58 species were recorded
during the surveys. Of these, 12 species were identified to be of commercial value, traded either locally
or regionally, and ten species (including one of known commercial value) were found within the MPA
site. Echinoderm diversity was largely divided into sea stars (Asteroidea, 19 species), sea urchins
(Echinoidea, 14 species), and sea cucumbers (Holothuroidea). Importantly, it was noted that while
Holothuroidea diversity was proportionally high (17 species), abundances of most of these sea
Figure 5Acropora spp., abundant at offshore reefs.
cucumbers were relatively low which was reflected in both roving and transect surveys. Crinoid,
Euryalid and Ophiurid diversity was proportionally low but likely strongly underrepresented, with the
taxonomy and systematics of these groups requiring a proportionally greater sampling effort, and
Ophiurids in particular being cryptic.
Among the best represented phyla in Escalante waters, 120 species of mollusc were found during the
surveys, with gastropods (94 species) making up the majority. The remaining diversity was comprised of
18 species of bivalve, seven species of cephalopod, and a single species of polyplacophoran (likely
highly underrepresented). Of these, 24 species were found to be of commercial value, and 10 species
(including one of commercial value) were found within the MPA. Interestingly, many of the mollusc
species found within the MPA were documented in the vast areas of soft sediment habitats and were not
documented outside the MPA. None of these, however, are known to be of conservation priority.
Documentation of the ecologically and commercially important group Tridacnidae (giant clams) is
discussed below.
Figure 6Gorgonocephalidae, Astroboa sp.
Figure 7 Goniodorididae, Trapania darvelli.
Figure 8 – Volutidae, Cymbiola vespertilio.
A relatively high diversity of Platyhelminthes was documented across the different habitats at Escalante
with 27 species recorded throughout, including two species within the MPA. Where possible, species
were identified based on currently available literature and close examination of their ventral surface and
photography of their dorsal surface. The taxonomy of many polyclad flatworms, particularly those in the
family Pseudocerotidae, awaits major updates as identification based on the external morphology of
many species remains unclear. The cryptic nature of many small and non-aposematic species strongly
suggests many more species are to be found in Escalante waters.
Other Groups
Not included in the above groups were those less represented in the overall diversity such as the single
species of bryozoan (Bugulidae sp.), a single Acoelomorphan species (Waminoa sp. Morphotype A, see
Kunihiro et al., 2019), two Nemerteans, two Ctenophora, nine Annelida, and 11 species each of Porifera
and Tunicata. A focused study on each of these groups will undoubtedly reveal greater diversity in the
area. The bryozoan, a few annelids and the abundant tunicate Didemnum molle were all found within the
MPA but 31 species were found only outside the area. The only species found to be of commercial value
not included in the larger phyla mentioned above were the algae of Caulerpaceae (particularly Caulerpa
racemosa) and Halymeniaceae.
Figure 9Epibiosis on the coral Goniopora by the tunicate Didemnum molle and by cyanobacteria.
3.2 - Ecological Assessment
Coral Reef
While the different coral dominated reefs at Escalante are highly variable in terms of homogeneity and
coral cover (Figs. 11 and 12), some common trends are visible throughout. The vast majority of coral
cover at Escalante occurs at depths shallower than 6m, usually showing an abrupt shift from coral
dominated substrate to soft sediments. This is particularly the case in the Northern half of the reefs
surveyed, with areas of extended coral cover becoming more common further south. In terms of coral
composition and community structure, reefs could generally be divided into the categories of nearshore
fringing reefs and offshore reef habitats, with the north-south trend particularly prevalent at the fringing
reefs. The offshore reefs tend to be more structurally complex (dominated by Acropora and Seriatopora
corals) and possess higher levels of homogeneity (Fig. 11). These reefs are found around areas where the
substrate becomes drastically shallower, often acting as submerged islets, and are frequently partially
exposed at the lowest tides. Fringing reefs, on the other hand, were found to be more heterogeneous,
often supporting a greater diversity of reef building hexacorals and hydrocorals (Millepora spp.). These
sites, particularly along the northern coast were found to be extremely limited in cover with very short
reef slopes, often reaching a maximum width of less than 50m for long stretches (Fig. 10).
Figure 10
Aerial imagery
highlighting the short
reef slope of the coastal
fringing reefs of
Escalante, rarely
exceeding 50m. Reefs
begin abruptly from
algal dominated
intertidal substrate and
rapidly shift to soft
bottom habitats at depths
greater than ~ 6m.
Figure 11 (Next Page)
Community structure of
reef building corals per
site, by proportional
cover of dominant
genera. Corals
comprising <10% at all
sites are grouped
together as ‘Other’.
Central % values
correspond to mean coral
cover per site.
Deeper substrate transects (6-8m) were only possible at three sites, with all other sites having little to no
coral cover beyond 6m depth (Fig. 12). As expected, coral cover declined with depth at each of these
sites. The aforementioned high variability in coral cover could not be explained entirely by any single
variable. For example, site ‘I’ (Seawall Reef) had the highest coral cover throughout the surveyed areas,
however, this was dominated by Porites corals with only a third of corals at the site belonging to any
other genus. Similarly, the second richest site in terms of coral cover was the offshore site ‘B’
(Malabagun Reef) which was dominated by Acropora corals with only approximately a third of other
corals contributing to the high coverage. The limited coral area within the MPA (site ‘E’) had a coral
cover of approximately 39% but was more than 75% dominated in Porites. Conversely, more
heterogeneous sites such as ‘D’, ‘K’ and ‘L’ (Cervantes, Buenavista, and Japitan) had an estimated coral
cover of 28%, 41% and 21% respectively but were each proportionally comprised of a greater diversity
of genera.
Figure 12 Mean coral cover per site at Escalante including three deeper sites (‘E’ MPA, ‘H’ Old
Poblacion North and ‘L’ Japitan). Error bars correspond to standard error.
Indicator Groups
Fish surveys at the sites also yielded high variation between sites (Fig. 13). Offshore reefs tended to
have greater abundances of indicator groups than nearshore reefs with notable exceptions to this being
sites ‘C’ (Jomabo Island, West) and ‘E’ (MPA). Unfortunately, a transect survey of indicator fish at the
southern-most site could not be conducted due to logistical constraints. With only a small coral-rich area
within the current MPA, the ability to isolate broader trends is limited. However, it should be noted that
in theory, all non MPA sites are under the same enforcement with regards to local and non-local fishing
activities as one another. Representatives of most indicator groups were found to be sold in the local fish
market (see below). All sites indicated depleted numbers of larger fish (>20cm) which may be
suggestive of fishing pressure throughout the unprotected (or less protected) waters at Escalante. Of
particular note are the mesopredator indicator groups of the Epinephelinae and Lutjanidae (groupers and
snappers) which are of widespread commercial value and are largely represented by smaller fish
(groupers) or relatively under-represented at all sites (snappers). Parrotfish populations were highest at
offshore sites ‘B’ and ‘G’ (Malabagun reef and Panansalan reef) with all other sites showing relatively
similar numbers. Data was collected on Rabbitfish populations, however, these are not represented here
as most sites showed negligible presence (mean <1 individual/100m3) and a single school of over 150
individuals from a single site skewed the results.
Figure 13 Mean number of fish per 100m3 surveyed area. Site name along x axis in accordance with
sites identified in Figure 2 and Table 1. Fish were classified as ‘Big’ if estimated to be of greater total
length than 20cm.
Data on reef-associated invertebrates revealed remarkably different trends. Of particular importance are
the heavily depleted populations of ecologically important species such as giant clams (Tridacninae) and
sea cucumbers (Holothuroidea) which were only found to be of greater abundance than one individual
per 100m2 at a few sites (Fig. 14). All species are regularly and abundantly collected from Escalante and
are considered relatively high value species in the local fishery. Boring clams (Tridacna crocea and T.
maxima) were most abundant at the offshore reef ‘A’ (Pamaawan reef), at only six individuals per
100m2, and giant clams (T. squamosa) were not found to be more abundant that 0.5 individuals per
100m2 at any reef in Escalante waters. Sea cucumbers were not found to be of greater abundance than
approximately two individuals per 100m2 (at ‘B’, Malabagun reef). Sea cucumbers of the family
Synaptidae were not included in this analysis as they were found to be of little to no commercial value at
Escalante. Abundances of Diadematidae urchins were not analysed as part of the present study but were
found to be high at most sites.
Figure 14 Mean abundance of Tridacninae and Holothurian spp. per 100m2 per surveyed site. Error
bars correspond to standard error.
Figure 15 Mean abundance of corallivorous echinoderms and the corallimorph P. hoplites per 100m2
per surveyed site. Error bars correspond to standard error,
Data was also collected on invertebrate predators of ecological importance (Fig. 15), namely the
corallimorph Paracorynactis hoplites, the corallivorous snails Drupella spp., and the corallivorous
echinoderms Acanthaster cf. solaris (crown of thorns sea star) and Culcita novaeguinea (cushion star).
Individuals of P. hoplites were found in the transects at only two sites (‘H’, Old Poblacion North and
‘L’, Japitan) and were entirely absent at other reef sites, including those surveyed by roving diver
surveys only. Very few individuals of the snail were found, all at a single site at Escalante (13
individuals at site ‘J’, Old Poblacion South) and were thus not compared with other sites. Individuals of
the crown of thorns sea star were documented from five sites with a maximum abundance of fewer than
2 individuals per 100m2 (at site ‘E’, within the current MPA). Abundances of the cushion star were
similarly variable and inconsistently distributed. It should be noted that this species was included despite
its broader dietary preferences, unlike the obligate corallivory of Drupella spp. and the crown of thorns,
as it is known to predate upon scleractinian corals as a significant part of its diet (Glynn and Krupp
1986). Coral ectoparasites (such as some nudibranch and Epitoniidae spp.) were observed but abundance
data was not collected. The recently described corallivorous nudibranch Phestilla viei (Mehrotra et al.,
2020) was observed upon eight colonies of the coral Pavona explanulata.
Spawning Events
Figure 16 – Egg bundle release of the scleractinian coral Montipora informis.
Alongside data on diversity of marine life and on coral reef health, data was collected on natural
spawning events. Seven nights of surveys from the full moon in early March yielded spawning of a
single colony of Montipora informis and partial spawning of a colony of Lobophyllia recta. Spawning of
both taxa was observed on the 7th of March 2018, 5 nights after the full moon (Fig. 16). Setting of M.
informis was observed at 18:14 hrs and the first egg bundles were released at 18:00 hrs. Spawning was
observed of the whole colony and lasted 11 minutes with approximately 95% of egg bundles being
released by 18:29 hrs. At 19:04 hrs, gamete release was observed across approximately 40% of a single
colony of L. recta. No other corals were observed to be spawning during this period and only a single
colony of either species was observed to spawn.
Figure 17 – Gamete release of the bivalve Beguina semiorbiculata (A, B) and the urchin Diadema
setosum (C, D).
During daytime transect surveys, a mass invertebrate spawning event was observed on the 14th of March
2018. At approximately 14:00 hrs in the Porites dominated reef habitats at site ‘E’ within the MPA,
synchronous spawning was observed in approximately 418 individuals of the urchin Diadema setosum
and 39 individuals of the bivalve Beguina semiorbiculata (Fig. 17). Overall gamete release lasted for
more than 90 minutes with the last confirmed release occurring at 15:38 hrs. Relatively few individuals
of Diadema savignyi (n = 42) and Echinothrix calamaris (n = 6) were observed at the location of the
event and of these only two individuals of D. savignyi and no individuals of E. calamaris were observed
to be spawning.
Other Habitats
Snorkelling surveys were conducted at a small number of nearshore and offshore mangrove sites. The
Escalante governing body has supported mangrove plantation activities with apparent success
throughout much of the coastline, however, these mangroves were found often to not extend far into
areas with large intertidal ranges. Offshore mangroves, and the few areas of mangrove growth that were
observed to be removed from the majority of onshore growth (i.e. those areas exposed to greater than
approx. 50cm of intertidal range) were observed to support greater abundances and diversity of fish,
including juveniles of commercial value in the region such as the Lutjanidae (Fig. 18). Areas where
mangroves were exposed to greater tidal variation were found at Jomabo Island, including some areas
within or fringing the eastern boundaries of the current MPA, and sporadically along the coastline south
of Old Poblacion.
Most of the benthic substrate at Escalante is unsurprisingly comprised of soft sediments, which support
distinctive habitats such as seagrass beds and other dynamic ecosystems. Extensive roving diver surveys
were carried out in these areas revealing relatively few seagrass habitats, largely concentrated around the
shallow and intertidal areas between the barangays Washington, Alimango, and Old Poblacion. This area
supports large populations of the sea slug Dolabella auricularia, the eggs of which are commercially
sold for consumption at Escalante and around much of the Philippines. In contrast, macroalgal
dominated substrates were abundant in the shallow reefs. Deeper soft sediment areas appeared to not
support other soft sediment suited colonisers such as hydrozoa, sponges or octocorals, or soft sediment
specific scleractinian corals such as Heteropsammia, Heterocyathus and some Fungiidae spp. An
exception to this latter category is the numerous but spatially widespread occurrences of the soft
sediment tolerant coral Trachyphyllia geoffroyi, though these were rarely clustered. Nonetheless, these
soft sediment areas did reveal multiple occurrences of charismatic and cryptic fauna.
Figure 18Offshore mangroves and those exposed to greater tidal submergence act as nurseries
to snappers (Lutjanidae), pufferfish (Tetraodontidae) and various Pomacentridae.
Transect and roving diver surveys within the MPA revealed the presence of 87 faunal taxa in the area,
12% of the total diversity recorded in the present surveys. Of these, 20 were not recorded in waters
outside of the MPA. Interestingly, these were mostly observed in open soft sediment areas and not
within the typically diverse coral reef habitats. As mentioned above, the limited reef habitats of the
MPA were found to be far more homogenous than other areas, dominated by Porites corals and other
massive or sub-massive colonies, with far fewer colonies of higher structural complexity. The diversity
in the soft sediment habitats included highly charismatic species but none that were found to be under
any particular pressure at Escalante (either via natural or anthropogenic means) such as the frogfish
Nudiantennarius subteres, seahorse Hippocampus kuda, and nudibranch sea slugs Aegires villosus,
Phidiana militaris, and Unidentia sandramillenae. Other charismatic species such as the sea snake
Emydocephalus annulatus, sea snail Naticarius onca and sea pen octocorals (Pennatulacea) were also
found in soft sediment habitats throughout Escalante but were not found from within the MPA.
3.3 - Fish market Assessment
A total of 94 species of fish were recorded from fish market surveys, of which 70 species were not
recorded from in-situ surveys conducted. Estimates of commercial value and of approximate catch by
weight was calculated for 39 species, with a further 29 species being sold as ‘mixed’ batches of multiple
different species, and thus data was extrapolated per species where possible. Estimates of commercial
value and weight for the remaining 26 species were either not available or were inconsistent, therefore
deemed unreliable and were excluded from analyses. A further 40 species of invertebrate were found to
be of commercial value (4 crustaceans, 12 echinoderms and 24 molluscs) as documented from a
combination of fish market surveys and BD patrols of illegal activity. These taxa were, however, also
excluded from the analysis of reef versus non-reef fish surveys. A number of taxa were observed in the
fishery worthy of additional note. Elasmobranchs of the families Dasyatidae and Rhinobatidae (Fig. 19)
were found as part of the catch, however, were not observed in-situ. No sharks were observed as part of
the catch during the survey period; however, these have been known to be recorded in the waters of the
area and regularly make their way to nearby markets (Mehrotra et al., 2016; 2017). Additionally, a
single individual of deep-water fish tentatively identified as Chauliodus cf. sloani (Fig. 20) was
recorded from the market, believed to be caught in the central Tañon Strait, within Escalante waters.
Figure 19Small Rhinobatos whitei for sale at the fish market at Escalante
Precisely half of the fish diversity documented from fish market surveys were categorised as reef fish,
and the other half as non reef-specific (Fig. 21). Of those that were found to be reef-specific, 17 species
were found to be of those groups considered as indicator species of ecosystem health in the above
documented reef transect surveys, with the remaining 30 species being considered non-indicator taxa.
The proportion of catch by weight and of commercial value as a whole for non-reef fish were
remarkably similar with 85.2% of the total fishery being comprised of non-reef fish which sold for
approximately 84.6% of the total economic value of the catch surveyed. These amount to approximately
1022kg of fish sold for PHP 137.9k and thus a crude estimation of approximately PHP 135 per kg of
fish. Reef-associated fish were also similar in their proportional weight and commercial value, making
up 7.8% of the catch (93.5kg) and sold for approximately 9.2% of the total value (approximately PHP
15k) and thus approximately PHP 160 per kg. The remaining catch were sold as mixed batches of reef
and non reef-associated species (i.e. not sold at a species-specific level) and thus contributed to both
categories in a significant but ill-defined way (7% of catch by weight, 6.2% of total value). Of the total
catch 4.4% of catch by weight and 5.2% of economic value were those fish considered as indicator
groups during transect surveys.
Figure 20Stomiidae, Chauliodus cf. sloani
Figure 21Diversity (A), proportional abundance (B) and economic value (C) of catch available at the
fish market at Escalante during the survey period. Economic value of catch is shown in PHP/1000 (i.e
total value of reef-associated catch = 14,950 PHP). Initial breakdown separates species as reef-
associated, non reef-associated, and sold as mixed lots of both groups (for definitions, see text). Reef-
associated species are further broken down into those families used as indicator groups (see Figure 13)
and non-indicator species.
Figure 22Fish traps supported by rocks, living and dead coral.
Figure 23Confiscated catch of reef fish, Tridacnid and gastropod spp.
Figure 24 Confiscated catch of Labridae including Choerodon anchorago.
4 - Discussion
4.1 - Ecosystem Health
The mean shallow (2-4m) hard coral cover (HCC) of all sites surveyed was approximately 40%,
however, this is subjective considering the extensive variability ranging from as low as 16% to as high
as 66%. There have been numerous assessments of how HCC reflects the broader reef health in the
Philippines, with among the most widely accepted assessment being that of Gomez et al. (1981) who
surveyed 619 stations across the Philippines. In the referenced assessment, it was concluded that reefs
with up to 24.9% HCC could be considered in ‘poor’ condition, 25-49.9% as ‘fair’, 50-74.9% as ‘good’
and HCC greater than this as ‘excellent’. They found the majority (~70%) of reefs could be classified as
either ‘poor’ or fair’. The recently updated nationwide survey of HCC in the Philippines by Licuanan et
al. (2017) resulted in over 90% of reefs being classified as ‘poor’ or ‘fair’ based on 166 stations. The
status of reefs at Escalante therefore align with the findings of previous localised and broad-scale
surveys (i.e. Verdadero et al., 2017), with the mean HCC being classified as ‘fair’ based on the
assessment scheme proposed by Gomez et al. (1981.H). However, these findings also show considerable
variability with reefs ranging from ‘poor’ (sites F, H, L) to ‘good’ (sites A, B, I) but no reefs being
classified as ‘excellent’. While few specific reefs in the Philippines have undergone long-term
monitoring efforts, the trend suggested by nationwide surveys indicates a dramatic decline in Philippine
reefs, a pattern documented throughout reef environments globally.
During the surveys conducted in Escalante, minimal incidences of coral bleaching or obvious coral
diseases were recorded (<1%). There does, however, exist anecdotal evidence by local surveyors of
widespread bleaching in recent years, though active documentation and assessment of this was not
carried out. In-spite of this, the reefs at Escalante were found to be under clear threat from
sedimentation and sediment-associated issues. Nearshore reefs, for example, were often subjected to
highly turbid conditions and often exposed to a high sediment load, possibly from onshore runoff, thus
acting as a local chronic stressor. Additionally, naturally occurring fragments of colonies were
perpetually found to be at risk of localised small-scale burial or were simply not exposed to sufficiently
stable substrate to continue to survive. Nearshore and offshore reef slopes alike were delineated by a
well-defined and often abrupt edge beyond which few colonies could survive, likely due to the lack of
stable substrate. Additionally, nearshore reefs in particular were found to host greater abundances of
sediment-tolerant corals such as Turbinaria and Porites.
Recent decades have provided numerous case studies on shifting community structure of coral genera in
tropical reefs, highlighting regional and sometimes broader trends of resilience of some genera over
others (i.e. McClanahan and Obura, 1997; Brown 1997; Riegl 1999; Marshall and Baird, 2000; Harriott
and Banks, 2002; Toda et al., 2007; Green et al., 2008; Baker et al., 2008; Adjeroud et al., 2009; Guest
et al., 2012; Scott et al., 2017a). For example, Porites corals are well documented in many of these cases
to be more tolerant to sediment inundation (among other stressors) than Acropora and this is largely
visible in the community structure of nearshore vs. offshore reefs at Escalante. However, we also see,
surprisingly, that surveyed sites closest to the river mouths at Escalante had the lowest abundances of
Porites and the offshore MPA had the highest. Therefore, its utility as an indicator genus for sediment
load input cannot be extrapolated alone. This agrees with the complexity of generalising such inferences
in reefs globally as it is also well documented that different genera respond differently in different
places, highlighting the need for a significant increase in coral community structure studies. Therefore,
while we may suggest that many of the dominant genera at Escalante have likely been influenced by
stressors such as sedimentation, thermal bleaching and storms, all of which are currently prevalent
threats in the region (Arceo et al. 2001; Yumul et al. 2011; Abreo et al. 2015) and likely to increase in
severity (Capili et al. 2005; Yumul et al. 2011), significantly more work is needed to tease out the local
ecological dynamics in the area.
Invertebrate transect surveys on the reef provided some of the most striking evidence for depletion of
important indicator groups, including species involved in nutrient cycling and filter feeding. Boring
clams (Tridacna crocea and T. maxima) and giant clams (T. squamosa and Hippopus hippopus) were all
found to be heavily depleted throughout the reefs of Escalante with mean densities of 0.79 and 0.06 per
100m2 respectively. These bivalves are well documented as ecologically important due to their capacity
in filter feeding (thereby helping to maintain the oligotrophic conditions of the reef), as sources of dense
and structurally complex substrate for coral recruitment, and as sources of zooxanthellae, facilitating
recovery of nearby corals after bleaching events (Neo et al. 2015; Neo et al. 2017; Morishima et al.
2019). Similarly, sea cucumbers which play an important role as detritivores and contribute to
bioturbation were not found in excess of two individuals per 100m2 (mean 0.42 per 100m2). Data was
also collected on the number of individuals of the strombid snails Lambis lambis and Strombus cf.
sinuatus due to their popularity in regional cuisine, however, almost no individuals were found in
surveyed reef or soft sediment environments (i.e. seagrasses). The loss of these commercially valuable
species is almost certainly due to exceptional over-harvesting (see below) and may endanger the
survivability of the populations of these animals in Escalante. It has already been shown that the waters
directly to the south of Escalante are also heavily depleted in clams and sea cucumbers (Mehrotra et al.,
2016; 2017) and thus are likely to show reduced potential for population recovery in the wider region.
Data was not collected on the populations of large barrel sponges (Xestospongia testidunaria) though
they too contribute greatly to filter feeding in reef environments (Schrope 2009).
Surveys on the density of predatory invertebrates often revealed greater abundances than the species
discussed above. For example, the crown of thorns sea star, a well-documented corallivore, was found at
between 0.5 to 1.5 individuals per 100m2 at five reef sites. While a specific carrying capacity for the
reefs around Negros have yet to be studied in great detail, these abundances are generally considered
low and are comfortably short of minimum outbreak parameters for most studied reefs in South-East
Asian reefs (i.e. de Dios et al., 2014; Scott et al 2017b). Populations of the cushion star Culcita
novaeguinea are less studied in the area and were found to be in high abundances at Escalante including
throughout seagrass, coral reef and some macroalgal/soft sediment ecosystems. This species, while
generally considered a corallivore, is also known to feed on a variety of other organisms (Bell 2008) and
has not been associated with large-scale detrimental outbreaks like the crown of thorns. Within the
surveyed coral reef habitats of Escalante, C. novaeguinea was found in remarkably similar abundances
to the crown of thorns, ranging from approximately 0.25 to 1.25 individuals per 100m2. It should be
noted, however, that the species was generally observed in greater abundances outside of dense coral
areas during daytime (during when transect surveys were conducted) and would increase within coral
reefs at night. The final predatory invertebrate surveyed was the corallimorph Paracorynactis hoplites,
which was primarily recorded from Old Poblacion North where its abundance did not exceed 0.75
individuals per 100m2 and some individuals recorded at Japitan. This species is currently believed to be
unique among tropical cnidarians due to its role as an opportunistic predator of the crown of thorns sea
star (Bos et al. 2011, de Dios 2015). While this dramatic example of ecological role reversal suggests a
biotic mechanism for population control of the often problematic predator, P. hoplites is also known to
predate upon a broad range of prey (Bos et al. 2011), and thus its ecological role in reef habitats needs to
be investigated further.
The observations of mass invertebrate spawning (Diadema setosum and Beguina semiorbiculata)
highlight the potential for the reefs and coastlines of Escalante to recover. Both species play an
important role in nutrient cycling of coral reef habitats and themselves contribute to the complexity of
the ecosystem by playing crucial roles in the trophic dynamics of coral reefs. Similarly, the spawning
observation of two scleractinian corals (Montipora informis and Lobophyllia recta) further support the
potential for recovery and growth of the coral reefs of Escalante. It should be noted, however, that the
spawning events were observed during an early full moon (early March) and at a nearshore reef facing
high turbidity. Synchronous coral spawning events in the vicinity of the coral triangle are known to
occur following the lunar cycle in March and April and thus the March full moon of 2018 falling
relatively early in the month may have resulted in immaturity of gametes and therefore a later spawning.
Additionally, the stress of turbid environments on coral spawning events has been studied (Erftemeijer et
al., 2012; Ricardo et al., 2015; Jones et al., 2015) and the partial-colony spawning of L. recta may be an
added indicator of turbidity related stress. One or both of these environmental factors may have
contributed to the sparsity of spawning recorded during the observation period and future investigations
into coral spawning events in the region should look into a wider window of observation.
Of the in-situ fish surveys, the most suggestive implications are best discussed in conjunction with
findings of the fish market surveys. Some results, however, are also clearly visible when considered
independently, namely the efficacy of the current MPA in supporting sustainability of the Escalante
fishery and the sparsity of larger individuals throughout. Regarding the former, the results strongly
indicate that during the survey period, the limited reef currently within the MPA (site ‘E’) did not
support fish populations any more effectively than any other site at Escalante. In fact, when combined
with all indicator fish groups, abundances of indicator fish within the MPA were found to be below the
mean for Escalante as a whole. The indicator group that appeared to be most abundant within the MPA
relative to all other sites surveyed were the groupers, however, no individuals larger than 20cm were
documented and a slightly greater abundance was documented at Malabagun (site ‘B’).
While we concede that a single measurement as an assumption of a generalisable tool as to what
constitutes a relatively ‘big’ fish for all species in all families is not suitable for all groups, a
conservative measure of 20cm was chosen so as to be theoretically applied to a majority of species
surveyed. Additionally, while not directly informing on true fish biomass, it allows for indications of
relative assessments between smaller and larger individuals of commercially valuable species in the
region. It has been shown for example (Mehrotra et al. 2017) that all families included as indicator fish
are caught and sold for consumption in local fish markets in Negros Occidental. It is therefore telling
that so few individuals of parrotfish, grouper, and snapper estimated to be of greater length than 20cm
were observed in the surveyed reefs, despite numerous species reaching sizes far larger being well
documented from the Visayas region. In a field where the problem of shifting baselines is pervasive and
where overexploited fisheries are known to result in reductions of mean fish size (see Pauly 1995;
Haedrich and Barnes 1997; Ainsworth et al., 2008; Knowlton and Jackson 2008; and others), it is vital
that more effort be applied in documenting size and abundance of commercially valuable species over
A remarkable discrepancy is present between the proportional diversity of catch and relative economic
value of fish sold in Escalante. While less than 10% of the total surveyed catch by estimated value and
biomass were classified as reef-associated, this was equivalent to a total of half of all species available
for sale. This, however, doesn’t include an additional 5-7% that were sold mixed with non-reef fish and
were thus difficult to isolate. The majority of nearshore fishing is broad and unregulated, with few
groups (cetaceans, turtles, etc.) illegal to land. Therefore, while many of the fish caught and sold may be
considered ‘bycatch’ elsewhere, all catch is landed to maximise profit, despite relatively low economic
returns. All fish found in the market were sold exclusively for consumption and not for souvenirs or the
aquarium trade, with families like small Labridae and Pomacentridae (particularly anemonefish of the
genus Amphiprion) and other ‘ornamental’ fish populations therefore being exposed to greater
anthropogenic pressures with minimal economic return. The majority of these fish were sold in the
‘mixed’ batches that were locally considered synonymous with miscellaneous and unknown fish and
ranged dramatically in price from approximately PHP 75-250 (USD 1.48-4.93) per kilo. This appeared
to be determined based on the relative size of the unknown fish but in general did not seem to follow any
pattern. In more rural areas in the region, the value of similar species may be as low as PHP 20 (USD
0.39) per kilo. A conclusive idea on the popularity of such fish in local cuisine was not assessed.
Nonetheless, the fact that more than 85% of the catch amounts to only 50% of the diversity suggests that
increased stringency in policy and enforcement on unregulated and illegal fishing on coral reefs could
result in improved protections for dozens of species with minimal economic loss.
As discussed above, many indicator species (both vertebrate and invertebrate) were found not only in
coral reef habitats but also in seagrass habitats. While abundance and density for these species was only
quantified from coral reef habitats, it should be noted that both coral reef and seagrass habitats at
Escalante are threatened by destructive and illegal fishing practices. Besides the active disturbance of
intertidal seagrass because of walking for collection of commercially valuable invertebrates, patrols with
the BD revealed incidences of seagrass raking, a highly destructive process used in the search of cockles
and other commercially valuable infaunal bivalves. An increase in patrols, however, appear to have
resulted in a reduction in such practices in recent years, with the most common outcome being a
confiscation of equipment and occasional impounding of boats. Though fishing-related disturbances in
seagrass habitats at Escalante are present, incidences of illegal methods such as raking were found to be
uncommon and often restricted to local communities. A practice that was found to be significantly more
frequent were incidences of subtidal collection of invertebrate taxa from coral reef habitats. These were
usually carried out during low tide by reef walking (at both nearshore and offshore locations), by
freediving, or by unsafe use of a boat-mounted compressor and a tube, and were usually carried out
alongside illegal deployment/recovery of fish cages within coral reef areas (Figs. 22-24).
Patrols with the BD found that illegal fishing from nearby or neighbouring municipalities was more
pervasive and was carried out at larger spatial scales across seagrass and coral reef habitats. This
includes the well documented, harmful practice of dynamite fishing, which is less regulated in some
other regions at Negros and was carried out near Escalante waters during the surveys discussed in this
report. Bottom trawling, historically carried out within Escalante waters, has been made illegal and was
not observed during the survey period, nor were indications of active trawling witnessed in-situ. The
combined impacts, however, of unregulated legal fishing, illegal fishing practices by the local
community, and illegal fishing within Escalante waters by non-locals is challenging to quantify. The
discrepancies between in-situ observations and estimated catch during illegal harvesting seen in BD
patrols in conjunction with results presented here from transect surveys and fish market surveys,
suggests parts of the nearshore fishery at Escalante are in dire straits. Of potentially greater importance
in the long term is the highly depleted populations of ecologically important species. A more sustainable
use of these remaining resources is likely to be crucial to support the economic and ecological future of
marine environments at Escalante.
4.2 - Zonation
On the 29th of October 2003 (ordinance no. 156) the governing body of Escalante declared a portion of
Escalante Bay as an MPA (CFRM 2008). Earlier that year, on the 2nd of January 2003, ordinance no. 141
declared the creation of the ‘Bantay Dagat Task Force’, which became the BD in operation today. It is
unclear to this day how or why this location was chosen, suffice to say that a disparity in Escalante
marine-resource information and protection initiatives existed. In its creation, numerous activities were
prohibited within the MPA, in an effort to preserve the area. These include prohibition of:
- All forms of fishing
- Collection of any organisms during low tide
- Taking any and all forms of marine species
- Constructions of fish corrals within 300 meters of sanctuary perimeter boundary—Buffer Zone
- Removal/destruction of coral reefs, sea grasses, other forms of vegetation
- Sand mining
- Water skiing
- “Dumping” (presumably of terrestrial waste)
Offenses resulted in a punishment of PHP 2000 or more and/or 3 months + in jail. Boats and all catch
were to be taken/impounded. It is believed that between the original designation of the MPA and
subsequent zonation strategies implemented, no in-depth investigation into marine ecosystem health has
been conducted. Therefore, it is unclear the extent to which any change has occurred, with regards to
most metrics assessed in the present study, as a result of the zonation strategies implemented at
Escalante in the past 15 years.
Our results suggest that, at least as of 2018, the currently positioned MPA (Fig. 1, also see Appendix I)
provides proportionally little to no benefit, either economically or ecologically, to the marine resources
of Escalante. While the size of the area is a significant portion of the total area of Escalante waters, it
was either accidentally or intentionally chosen to cover among the smallest areas of structurally complex
and ecologically diverse habitats possible, with the majority covering bare soft sediments. By almost
every measure, the MPA in its current form falls short of the average diversity and abundance of marine
resources available at Escalante, and thus plays little more than a figurehead role as a measure of
protection for the marine resources in the area. This unfortunately agrees with a broader trend visible
regionally and locally (Aliño et al., 2002; Horigue et al., 2012; Mehrotra et al., 2016; 2017). Throughout
the coral triangle, MPAs are set up to promote economic and/or ecological sustainability (White et al.,
2014), usually assessed by population growth of key organisms of interest. This may be achieved via
passive means in combination with active means.
Passively, a given area may be subject to stringent legal protections, prohibiting or penalising certain
activities, and is often something that is influenced by both local and regional policy. For example,
Escalante is located within the Tañon strait, and thus local management strategies are mandated by
regional goals such as by the broader Tañon Strait Protected Seascape management plans (TSPS-GMP
2015). Additionally, nationwide initiatives such as the recent ‘Expanded National Integrated Protected
Area System Act (E-NIPAS, Republic Act 11038, amendment to Republic Act 7568) mandates an
increase in the area legally protected for biodiversity conservation throughout the Philippines, and
strengthens stringency of penalties and fines (see RA 7658; La Viña et al., 2010; Mayuga 2018), though
these measures are largely without teeth in the absence of active measures of protection.
Passive (often synonymous with policy-driven) measures provide a pathway and act to legitimise active
means of protection. Active measures are locally driven and require local enforcement as a primary
imperative, particularly in areas where site-specific threats are anthropogenic in nature. A lack of
effective enforcement and management is a leading cause of failure in MPA initiatives, in the
Philippines and beyond (Aliño et al., 2002; Cabigas et al., 2012; Maypa et al., 2012). Other forms of
active management include habitat restoration, regular monitoring, mitigation of non-anthropogenic
threats (i.e. disease) and others, however, all these require extensive training to be effective instead of
At present, Escalante has an active enforcement body (Bantay Dagat) as well as some onshore habitat
restoration programmes (mangrove transplanting). Surveys of habitats across the region indicate a
wealth in some marine resources (i.e. coral cover, invertebrate biodiversity) and severe depletion in
others (i.e. commercially valuable fish and invertebrates). However, current trends of legal and illegal
fishing efforts, lack of sub-tidal restoration efforts and, in particular, ineffective zonation strategies
regarding protection suggest a reduced capacity for sustainable coastal resource management. Therefore,
we here provide proposed amendments to the designated MPA zonation in Escalante and some
additional measures that may be pursued to facilitate effective marine resource management in the area.
The present MPA is 1323.5 hectares in area. Following this measure as an upper bound, we propose an
alternate zonation (NMPA1) based on the findings on the surveys conducted (Fig. 25). This strategy
supports the creation of 10 smaller MPAs along the coast of Escalante, including three larger offshore
areas. The combined area under this proposal is 1000 hectares in size, a reduction of almost 25% from
the currently designated area. This proposition relies on the premise that more effective placement and
management of MPAs can yield far greater results, despite a coverage of only 75% of the original area.
Additionally, these smaller MPAs have been designed so as to have minimal overlap with the current
zonation plan and may be managed as an extension of mangrove and mariculture zones already in place.
Crucially, this proposal relies on involvement from all coastal barangays (each would be required to
manage their own area) in addition to a broader city responsibility which would ideally manage the
larger offshore areas.
Figure 25 The first alternate MPA zonation proposal (NMPA1) overlaid in blue on a summarised
version of the current zonation at Escalante.
We also propose a second, alternative zonation (Fig. 26), that would support remediation of major
oversights in the current MPA placement (NMPA2). We do, however, concede that this second
alternative would be less effective at achieving sustainability and recovery of marine resources at
Escalante than NMPA1 and should only be considered if the previous proposal does not pass the
implementation process. The total area covered by NMPA2 is 1251 hectares which amounts to a
reduction in area of over 72 hectares from the current MPA. The major change from the current MPA
would be a drastic reduction in protections offered further offshore, which could re-open as deregulated
waters, and move the protections to include the seagrass, mangrove and coral reef habitats around
Pamaawan, Malabagun, Jomabo, Paliswihan and Panansalan. This would involve the reclassification of
the single mariculture zone at Panansalan and would encompass the tourism zone at Jomabo, though it
could be regulated such that the tourism zone at Jomabo could be synergised with the updated zonation
so as to reinforce both tourism and regulated protection within the area (see below).
Figure 26 - The second alternate MPA zonation proposal (NMPA2) overlaid in blue on a summarised
version of the current zonation at Escalante.
Both proposals NMPA1 and NMPA2 (coordinates in Appendix II) would better reflect the purpose of a
marine protected area by promoting preservation of threatened habitats, while also providing safe habitat
for fish. Offshore mangrove and coral reef habitats in particular act as important nursery sites for
juvenile fish, including those of relatively high commercial value, and would therefore promote recovery
of the depleted fishery in the area. Crucially, active enforcement of such areas may allow for a return of
key invertebrate groups such as giant clams and sea cucumbers that play important roles in nutrient
cycling. Ecologically, both proposals would include far greater proportions of threatened ecosystems
that in turn could be used to support economic growth via tourism, when regulated. The current policy of
enforcement (highlighted above) is largely reactive and relies heavily on regulation of detrimental
activities or penalising illegal ones and we were unable to find any proactive management initiatives tied
to the mandate of the current MPA. Therefore, we have suggested an expansion of policy ideas to be tied
to the management and/or creation of further MPA zonation process going forwards. The following
amendments to local policy, in conjunction with the newly designated area(s), would also greatly
support a more sustainable use of marine resources in the area.
1) A stringent and enforced regulation on diversity and biomass of catch from any fishing or
collection from coral reef or offshore (subtidal) mangrove areas. This should extend to all such
habitats both within and outside of MPAs, with ideally a complete ban from within MPA areas.
2) Direct involvement from barangays in sustainable use and protection of any and all MPAs.
3) Implementation of regular monitoring efforts from all habitat types, within and outside of MPAs.
4) Participation in active offshore restoration efforts such as artificial reef and substrate deployment,
offshore mangrove transplantation and other restocking efforts.
5) A comprehensive and stringent set of guidelines, with enforcement, on regulated activities within
MPAs and threatened habitat areas (particularly coral reef, mangrove and seagrass habitats).
These should involve stakeholder involvement with the clear understanding of purpose and
should then be followed by a comprehensive dissemination of these guidelines throughout
relevant bodies in Escalante.
6) Increased infrastructure and investment in promoting marine tourism activities, following
sustainable guidelines for ecosystem and MPA use.
7) Creation of more permanent moorings within MPA areas, for Bantay Dagat use only, and a
complete ban on anchor dropping from within coral reef and seagrass habitats.
Some of these aspects are expanded below.
4.3 - Steps Towards Sustainability
1) Enforcement
Regulation on catch, particularly from all coral reef areas would have proportionally low economic cost
(see Fig. 21) and could promote long term recovery and growth of the commercially valuable fishery.
Regulation should involve, at minimum, a ban on the sale of several ecologically important fish types
and juveniles of commercially valuable species. Additionally, a release program for low-value/non-
target species should be implemented, including juvenile and sub-adult individuals of commercially
valuable species, such that the broader fishery may be sustained. When carried out in conjunction with
habitat protection and restoration initiatives, these measures could improve the sustainability of the
coastal fishery at Escalante dramatically.
A collaborative effort between the Bantay Dagat, captains of coastal barangays, fisherfolk and Escalante
government would allow for an effective and integrated management and monitoring effort across all
relevant zones. Additionally, input should be sought from an environmental or conservation focused
body, well versed in marine ecology, to provide expertise from an ecological perspective. This taskforce
should be responsible for the creation of guidelines of marine resource use, both within and outside of
protected areas, and the creation of effective management plans for key areas of interest in Escalante
waters. Management plans should include the following considerations:
2) Monitoring
A lack of comprehensive and regular monitoring has facilitated uninformed resource use decisions at
Escalante thus far, which in turn has likely contributed to many of the challenges faced today. Certainly,
this fact resulted in the current MPA zonation scheme in place which has little possible support by data
on resources and need for protection within. Aguilar and Villamor (2010) provide one of numerous
examples in the Philippines where a lack of monitoring renders protection and enforcement efforts
largely redundant for diverse marine communities. At present, only a single attempt can be found to
assess and document broadly the marine resources at Escalante (CFRM 2008), however, this provides
little detail regarding assessments of ecologically important groups or threats and nothing specific from
within the MPA.
Appropriate habitat-specific monitoring protocols need to be applied to each of the three main marine
ecosystems at Escalante (coral reef, mangrove, and seagrass) as well as biodiversity assessments at other
habitat types (such as soft sediment and soft coral dominated). Established protocols designed around
specific habitats would be best suited to acquiring the most relevant information. A focus on
ecologically and economically important key indicator groups, such as those directed by the ecological
monitoring protocol used (Scott 2012), would allow for broader inferences to be made such as isolating
sources of disturbance. This would also allow a targeted comparison between preceding surveys (such as
the baseline provided here) and subsequent surveys to document change over time. Crucially,
monitoring efforts should be carried out both within and outside of designated protected areas to assess
efficacy, and the governing body should remain transparent with monitoring and management outcomes
resulting from within these areas. Finally, protocols and specific tools should be standardised across all
barangays/monitoring bodies (and subsequently each independently monitored zone) so that information
may be compared and combined during assessments. It is only with rigorous and systematic assessments
that appropriate management and restoration efforts can be applied. These may further inform a core
strategy of best practices to be followed by anyone engaging with the marine environment.
3) Management
Alongside monitoring, targeted restoration efforts would actively and dramatically improve the outcome
of recovery and growth of much of the depleted marine resources at Escalante. Numerous proactive
efforts can be employed to increase resilience, such as the creation of permanent/semi-permanent
moorings at MPAs and areas of sensitive substrate. These would allow for easier monitoring and
enforcement by the Bantay Dagat and other relevant bodies and, most importantly, would reduce the
need for anchoring at these sites. At present, dropping anchor is common throughout the vast majority of
Escalante and damage to sensitive marine habitats such as seagrass beds, soft coral and hard coral
habitats was apparent. While these appear to by no means be the leading cause of habitat loss, they are a
relatively simple problem to solve, such as by the creation of moorings or even by deploying of anchor
further away from the often small areas of habitat. The deployment of permanent moorings could be tied
into a larger and significantly more important effort, that being the creation of more stable substrate.
Artificial reefs have been deployed in waters throughout the globe, and when maintained properly, have
been shown to have incredible potential for recovery and long-term improvements in localised
biodiversity and fish abundances (Seaman and Sprague 1991; Rilov and Benayahu 2002). Much of the
coastline of Escalante was found to be ideal for the deployment of artificial substrate due to the shallow
and well-defined reef edge throughout most of the coral reef areas, followed by extensive, largely barren
sandy areas. The deployment of non-plastic and inert, stable substrate would, in the short term, promote
rapid colonisation by numerous fish and invertebrate groups. In the long term, these structures could act
as extremely important substrate for the settlement of coral recruits and other important invertebrates.
New genetic material will be vital in reef ecosystem adaptability to both local and global threats (Baums
2008), and with some spawning already observed, there is strong evidence that substrate availability will
promote coral recruitment.
Heavily depleted groups would also benefit from active restocking of wild populations. Key examples of
this include large bivalves such as the giant clams (Tridacnidae) and sea cucumbers. Large bivalves
contribute significantly to water quality due to their filter feeding nature and, in particular, giant clams
have been shown to be extremely important to coral reef areas. Similarly, the importance of sea
cucumbers has also been discussed with many known to contribute greatly to organic matter cycling in
various benthic environments. While the restocking of both these groups from ex-situ rearing efforts
would not only drastically improve the chances of population recovery in the natural environment,
eventually (such as in the case of sea cucumbers), the investment of restocking would allow for long-
term economic return from sustainable resource use.
4) Maintenance
By far, the leading uses of marine resources at Escalante are exploitative and extraction based (fishing
and collection being the largest contributor). It is a well-established perception at Escalante (and nearby
Toboso, see Mehrotra et al., 2016; 2017) that a generational decline in the abundance of fish catch has
resulted in a reduction in fishing communities, with many residents seeking alternative livelihoods such
as agriculture. At present, there is very little marine-based tourism at Escalante. Our findings suggest
that a wealth of diversity at Escalante could promote an active tourism industry if more infrastructure
were made available. If tourism activities were regulated and sustainability promoted as a priority,
marine tourism at Escalante could be a source of income that could support enforcement and
management costs incurred, such as those of the Bantay Dagat, or materials for deployment. One such
area of high potential value would be the current MPA which, despite hosting little structurally complex
habitat, was found to host a remarkable array of non-sessile charismatic fauna. Sea slugs, frogfish,
octopus and seahorses were observed residing on the soft sediment habitats north of Jomabo island and
are all contributors to a 150 million USD tourism industry of sediment habitats (De Brauwer et al. 2017).
Tourism leveraging these habitats could be easily regulated and would avoid incurring the tourism-
related damages to more sensitive benthic habitats. Models such as those highlighted by Huang and
Coelho (2017) can be taken into consideration to maximise efficacy of such ventures and can in turn be
used to support employment opportunities in marine environments in less exploitative ways.
Figure 27Some charismatic species of known popularity to the recreational SCUBA industry in the
Philippines, all recorded from Escalante waters.
Solenostomidae, Solenostomus paradoxus
Facelinidae, Phidiana militaris
Palaemonidae, Periclimenes colemani
Antennariidae, Lophiocharon lithinostomus
5 - Conclusion
The waters of Escalante have a wealth of faunal diversity, including many species of particular
ecological and economic value. Despite active enforcement against illegal fishing activities, resource
extraction from the marine environment, particularly in the form of fishing pressure, has left many of
these ecologically and economically important species in dire straits. The current MPA offers little to no
benefit in the protection of the ecologically and economically important species of Escalante’s waters.
Our proposed zonation of the Marine Protected Area to be redistributed along the coast offers a more
effective placement and, with the involvement of the barangays and the BD, would facilitate the
preservation of threatened habitats, a safe habitat for fish, and recovery of this invaluable ecosystems
and the depleted fishery. Escalante’s current biodiversity offers a wide diversity of hard coral and
charismatic species that have intrinsic value in the tourism industry. Effective management and
protection of these waters offer not only the recovery of the fishing industry, but an opportunity for
economic benefits associated with ecotourism as well. It is crucial that this reallocation of the MPA be
coupled with enforcement, monitoring, management and maintenance, including increased policy and
enforcement on unregulated and illegal fishing as well as the instillation of permanent mooring lines to
be used by the BD in place of dropped anchors. Escalante’s location and rich diversity provide an
opportunity for improvements in ecological and economic sustainability and highlight the importance of
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Appendix I
Complete zonation map of Escalante waters, as provided by Escalante city.
Appendix II
Table of coordinates corresponding to proposals NMPA 1 and NMPA2 (see Figures 25 and 26).
Size (ha)
10°54'30.00"N - 123°33'19.00"E
10°52'60.00"N - 123°32'00.00"E
10°54'41.00"N - 123°33'34.00"E
10°52'20.00"N - 123°32'00.00"E
10°54'35.00"N - 123°34'4.00"E
10°52'9.00"N - 123°32'8.00"E
10°54'28.00"N - 123°34'26.00"E
10°52'10.00"N - 123°32'20.00"E
10°54'12.00"N - 123°34'34.00"E
10°53'0.00"N - 123°32'15.00"E
10°51'4.00"N - 123°34'18.00"E
10°50'53.00"N - 123°33'17.00"E
10°54'30.00"N - 123°33'19.00"E
10°51'12.00"N - 123°33'12.00"E
10°54'41.00"N - 123°33'34.00"E
Total Area
10°54'35.00"N - 123°34'4.00"E
10°54'28.00"N - 123°34'26.00"E
10° 53'16.60"N - 123°33'51.00"E
10° 53'16.60"N - 123°33'51"E
10° 52'50.0"N - 123°34'14.00"E
10° 52'38.0"N - 123°33'27.00"E
10° 53'00.0"N - 123°33'18.00"E
10° 51'20.0"N - 123°33'13"E
10° 51'40.0"N - 123°33'50"E
10° 51'30.0"N - 123°34'00"E
10° 51'3.0"N - 123°33'32"E
10° 51'1.00"N - 123°34'15.00"E
10° 51'00.0"N - 123°34'00"E
10° 50'40.0"N - 123°34'5.00"E
10° 50'41.5"N - 123°34'15.00"E
10° 50'00.0"N - 123°34'20"E
10° 50'00.0"N - 123°34'10"E
10° 49'40.0"N - 123°34'10"E
10° 49'30.0"N - 123°34'00"E
10° 49'30.0"N - 123°34'13"E
10° 48'45.0"N - 123°33'48.00"E
10° 48'15.0"N - 123°33'55.00"E
10° 48'20.0"N - 123°34'4.00"E
10° 48'43.0"N - 123°34'1.00"E
10° 47'20.0"N - 123°33'50"E
10° 47'10.0"N - 123°33'50"E
10° 46'30.0"N - 123°33'40"E
10° 46'30.0"N - 123°33'48"E
10° 47'20.0"N - 123°33'58"E
10° 45'43.0"N - 123°32'54"E
10° 45'20.0"N - 123°32'54"E
10° 45'6.0"N - 123°32'45"E
10° 45'35.0"N - 123°33'15"E
10° 45'0.0"N - 123°33'12"E
10° 52'52.25"N - 123°34'41.00"E
10° 52'50.0"N - 123°34'14.00"E
10° 51'56.0"N - 123°33'38.00"E
10° 51'32.0"N - 123°34'28.00"E
Total Area
University of the Philippines Cebu
Conservation Diver
Love Wildlife Foundation, Thailand
ResearchGate has not been able to resolve any citations for this publication.
Full-text available
Unlike most bivalve shellfishes, giant clams (tridacnines) harbor symbiotic microalgae (zooxanthellae) in their fleshy bodies. Zooxanthellae are not maternally inherited by tridacnine offspring, hence, the larvae must acquire zooxanthellae from external sources, although such algal populations or sources in the environment are currently unknown. It is well known that giant clams expel fecal pellets that contain viable zooxanthellae cells, but whether these cells are infectious or just an expelled overpopulation from the giant clams has not been investigated. In this study, we observed the ultrastructural and photosynthetic competencies of zooxanthellae in the fecal pellets of Tridacna crocea and further tested the ability of these cells to infect T. squamosa juveniles. The ultrastructure of the zooxanthellae cells showed that the cells were intact and had not undergone digestion. Additionally, these zooxanthellae cells showed a maximum quantum yield of photosystem II (Fv/Fm) as high as those retained in the mantle of the giant clam. Under the assumption that feces might provide symbionts to the larvae of other giant clams, fecal pellets from Tridacna squamosa and T. crocea were given to artificially hatched 1-day-old T. squamosa larvae. On the 9th day, 15-34% of the larvae provided with the fecal pellets took up zooxanthellae in their stomach, and on the 14th day, zooxanthellae cells reached the larval margin, indicating the establishment of symbiosis. The rate reaching this stage was highest, ca. 5.3%, in the larvae given whole (nonhomogenized) pellets from T. crocea. The composition of zooxanthellae genera contained in the larvae were similar to those in the fecal pellets, although the abundance ratios were significantly different. This study is the first to demonstrate the potential of giant clam fecal pellets as symbiont vectors to giant clam larvae. These results also demonstrate the possibility that fecal pellets are a source of zooxanthellae in coral reefs.
Full-text available
Giant clams, the largest living bivalves, play important ecological roles in coral reef ecosystems and provide a source of nutrition and income for coastal communities; however, all species are under threat and intervention is required. Here, we re-examine and update their taxonomy, distribution, abundance and conservation status as a contribution to the protection, rebuilding and management of declining populations. Since the first comprehensive review of the Tridacnidae by Rosewater (1965), the taxonomy and phylogeny of giant clams have evolved, with three new species descriptions and rediscoveries since 1982 represented by Tridacna squamosina (formerly known as T. costata), T. noae and T. lorenzi. Giant clams are distributed along shallow coasts and coral reefs from South 88 MEI LIN NEO ET AL. Africa to the Pitcairn Islands (32°E to 128°W), and from southern Japan to Western Australia (24°N to 15°S). Geographic distribution of the 12 currently recognized species is not even across the 66 localities we review here. Tridacna maxima and T. squamosa are the most widespread, followed by the intermediate-range species, T. gigas, T. derasa, T. noae, T. crocea and Hippopus hippopus, and the restricted-range species, Tridacna lorenzi, T. mbalavuana, T. squamosina, T. rosewateri and Hippopus porcellanus. The larger species, Tridacna gigas and T. derasa are the most endangered, with >50% of wild populations either locally extinct or severely depleted. The smaller and boring species, such as T. maxima and T. crocea, remain relatively abundant despite ongoing fishing activities. Population density also varies across localities. Areas with the lowest densities generally correspond with evidence of high historical exploitation intensity, while areas with the highest densities tend to be within marine reserves, remote from human populations or have low historical fishing pressures. Exploitation continues to be the main threat and conservation challenge for giant clams. Harvesting for subsistence use or local sale remains an important artisanal fishery in many localities; however, increased commercial demand as well as advances in fishing, transport and storage practices, are in large part responsible for the ongoing loss of wild populations. Habitat loss and a suite of other anthropogenic stressors, including climate change, are potentially accelerating stock depletions. Despite these challenges, global efforts to protect giant clams have gained momentum. CITES Appendix II listings and IUCN conservation categories have raised awareness of the threats to giant clams and have contributed to stemming their decline. The continued development of mariculture techniques may also help improve stock numbers and lend populations additional resilience. However, more effective implementation of conservation measures and enforcement of national and international regulations are needed. It is clear that active management is necessary to prevent the extinction of giant clam species as they continue to face threats associated with human behaviours.
Full-text available
The establishment of marine protected areas (MPAs) can often lead to environmental differences between MPAs and fishing zones. To determine the effects on marine dispersal of environmental dissimilarity between an MPA and fishing zone, we examined the abundance and recruitment patterns of two anemonefishes (Amphiprion fre-natus and A. perideraion) that inhabit sea anemones in different management zones (i.e., an MPA and two fishing zones) by performing a field survey and a genetic parent-age analysis. We found lower levels of abundance per anemone in the MPA compared to the fishing zones for both species (n = 1,525 anemones, p = .032). The parentage analysis also showed that lower numbers of fishes were recruited from the fishing zones and outside of the study area into each anemone in the MPA than into each anemone in the fishing zones (n = 1,525 anemones, p < .017). However, the number of self-recruit production per female did not differ between the MPA and fishing zones (n = 384 females, p = .516). Because the ocean currents around the study site were unlikely to cause a lower settlement intensity of larvae in the MPA, the ocean circulation was not considered crucial to the observed abundance and recruitment patterns. Instead, stronger top-down control and/or a lower density of host anemones in the MPA were potential factors for such patterns. Our results highlight the importance of dissimilarity in a marine environment as a factor that affects connectivity. K E Y W O R D S coral reef fish, larval dispersal, microsatellites, parentage analysis, Philippines
Full-text available
The present study shows the status of certain reefs of Batangas and northern Palawan using data gathered with volunteers, community members, local governments, and civil society groups utilizing Reef Check ® methods. Both provinces have mean densities of less than 1 per 100 m 2 for most of the fish and invertebrate indicators—signifying that they are overfished. Batangas is an urbanized province with an average hard coral cover of 40% (n = 22 sites from three towns and one city). Northern Palawan reef assemblages were generally distant from centers of population and have a higher average hard coral cover of 53% (n = 29 sites from five towns). According to Gomez et al.'s (1981) categories based on live coral cover, the reefs of northern Palawan are in " good " health, while those in Batangas are said to be " fair. " Conversely, in terms of the Coral Reef Health Index (CRHI), the coral reef assemblages of Batangas are in " good " health (CRHI = 10), while those in northern Palawan are in " poor " health (CRHI = 8)—despite the latter's higher coral cover. The difference between the overall health of the provinces' coral reef assemblages seems to be attributable to the biases of the indices used. Overfishing, overexploitation, siltation, and destructive fishing methods remain to be the most prevalent anthropogenic disturbances acting on the reefs for both provinces.
Full-text available
Global coral reef related tourism is one of the most significant examples of nature-based tourism from a single ecosystem. Coral reefs attract foreign and domestic visitors and generate revenues, including foreign exchange earnings, in over 100 countries and territories. Understanding the full value of coral reefs to tourism, and the spatial distribution of these values, provides an important incentive for sustainable reef management. In the current work, global data from multiple sources, including social media and crowd-sourced datasets, were used to estimate and map two distinct components of reef value. The first component is local “reef-adjacent” value, an overarching term used to capture a range of indirect benefits from coral reefs, including provision of sandy beaches, sheltered water, food, and attractive views. The second component is “on-reef” value, directly associated with in-water activities such diving and snorkelling. Tourism values were estimated as a proportion of the total visits and spending by coastal tourists within 30 km of reefs (excluding urban areas). Reef-adjacent values were set as a fixed proportion of 10% of this expenditure. On-reef values were based on the relative abundance of dive-shops and underwater photos in different countries and territories. Maps of value assigned to specific coral reef locations show considerable spatial variability across distances of just a few kilometres. Some 30% of the world's reefs are of value in the tourism sector, with a total value estimated at nearly US$36 billion, or over 9% of all coastal tourism value in the world's coral reef countries.
Full-text available
Diving-related tourism is known to contribute both directly and indirectly to reef degradation around the globe, including Koh Tao, a popular diving destination in the Gulf of Thailand. Of the known publications on reef threats at Koh Tao, only three mention the effects of highly abundant coral predators. The present study combines results of a nine-year long period (2006–2014) of reef surveys to evaluate the abundance and impact of corallivorous Drupella snails and Acanthaster sea stars in this area. It also provides the first record of their simultaneous outbreaks on Koh Tao's reefs. The results are compared to those of other studies in order to evaluate how coral predation has influenced declines in reef health. The findings suggest that the combined effect of these corallivores has contributed substantially to coral degradation over the last decade and indicate that future assessments of reef decline in areas impacted by heavy tourism also need to address the effect of coral predation.
Paracorynactis hoplites is one of the natural predators of Acanthaster planci. Hence, this study offers a new knowledge on the predation and feeding behavior of P.hoplites on A. planci in Sogod Bay, Southern Leyte, Philippines. Three different individuals of P.hoplites located in the reef crevices of the fringing reef of Balong-balong, Pintuyan, So. Leyte were fed in situ with adult size A. planci (diameter in cm: 23.75±0.44, mean±SE) in the morning and in the afternoon for the months of Mar 2015 and Jun 2015. The feeding behavior and predation of polyps P. hopliteson A. planci were observed using SCUBA and were video/photo documented for less than 40 minutes using the underwater camera. The polyp P. hoplites extended to reach the prey and pulled A. planci towards the mouth, swallowed and ingested completely. It took about 17.378 to 29.382 min(95% CI) to complete ingestion in the morning and 17.582 to 37.991 min(95% CI) in the afternoon and showed no significant difference using paired t-test (t=0.337; p=0.308). However, the time to complete the ingestion of A. planci by P. hoplites in day one was significantly different from day two (t=0.167; p=0.041) showing that the predator was satiated with its prey but still capable of capturing/killing its prey. Ingestion on day one took 18.603 to 25.862 min(95% CI) and 23.434 to 31.683 min (95% CI) for day two. In the afternoon of the second day, the undigested parts of A. planci composed of spines and calcium carbonate skeleton/test were regurgitated into the sand near the polyp.
The genus Waminoa currently contains two described species, which each contains two types of endosymbiotic algae. Waminoa individuals are basically brown in body color, derived from these algal symbionts, and their body shape has been described as "discoid to obcordate". They have been found as associates of various anthozoans (Cnidaria) in the Indo-Pacific Ocean and the Red Sea. In order to reveal the diversity of the genus Waminoa and their hosts, we conducted phylogenetic and morphological analyses on acoelomate flatworms specimens collected from Japan, Palau and Indonesia. At least 18 Waminoa morphotypes were found on at least 20 anthozoan host species, and two specimens were found on species of two sea stars. Overall, there were two main body shapes of specimens; obcordate, as seen in W. litus and W. brickneri, and the other molar-like with an elongated body. These two body shapes each represented a separate clade in 18S rDNA and mitochondrial cytochrome c oxidase subunit 1 (COI) phylogenetic trees, with W. brickneri included in the obcordate subclade. Automatic Barcode Gap Discovery (ABGD) analyses on COI sequences of our specimens revealed the presence of at least five operational taxonomic units (OTUs). These five OTUs consisted of one large group of all obcordate animals, three OTUs consisting of one specimen each within the molar-like clade, and one large group of the remaining molar-like specimens. Both clades contain numerous morphotypes and were associated with a variety of hosts. Finally, based on genetic distances, the molar-like specimens are considered as an unnamed genus group separate from Waminoa, which needs to be clarified in future studies.
Most of the marine protected areas (MPAs) in the Philippines are small-sized and community-based, and their contribution to the conservation efforts have been usually overlooked. This paper will present the results of the biological assessment study conducted in three community-based MPAs in Southern Iloilo, Philippines. Each MPA has a 2-ha no-take zone and this size is way below the recommended optimal size of 10–100 km². Results show that fish biomass showed an overall increase of about 1–5 times. This is attributed to both an increase in abundance and in fish size. Fish in this survey conducted in 2013 were about 2.3–3.3 times the size of fish in the 2007 baseline data. Macroepifaunal abundance increased 2 to 8 times across the three MPA sites. However, live hard coral cover showed a parallel ∼40% decrease across all sites, which can be attributed to several factors. The conservation goals of these MPAs have been attained. However, the results of biological assessments still need to be correlated with a study on the socioeconomic impact of the MPAs in the community to be able to arrive at good management decisions.