Status of Philippine reef fish communities
Vincent V Hilomen1, Cleto L Nañola, Jr.2 and Arvin L Dantis3
1
Institute of Biological Sciences, UP Los Baños, College, Laguna, 4031
2
College of Science and Mathematics, UP Mindanao, Davao City
3
Marine Science Institute, UP Diliman, Quezon City
ABSTRACT
Fish visual census data from various projects between 1986 and 1999 were evaluated for species
richness, abundance and biomass to assess status of reef fish communities in the Philippines. A
total of 915 species were recorded in 570 transects representing about 60% of reef-associated
species worldwide. Nearly 75% of transects (n=539) examined for species richness fell under
the very poor, poor and moderate categories (<26, 27-47 and 48-74 species 1000m-2,
respectively) and only 25% under the high and very high categories (75-100 and >100 species
1000m-2, respectively). About 70% of transects (n=504) examined for fish abundance were in
the very poor, poor and moderate categories (<201, 202-676 and 677-2267 individuals 1000m-2,
respectively), and 30% under the high and very high categories (2268-7592 and >7592
individuals 1000m-2, respectively). Nearly 90% of transects (n=227) examined for biomass fell
under the very low, low and moderate categories (<5.0, 5.1-20.0 and 20.1-35.0 mt km-2,
respectively) and only 11% under the high and very high categories (35.1-75 and >75 mt km-2,
respectively). The condition of reef fish communities in majority of reef areas is poor. The need
to urgently protect the few remaining healthy fish communities is discussed. This study has
strong implications to management.
Keywords: Philippine reef fish, fish assemblages, fisheries management, fish biomass, fish
abundance, species richness
Date of project completion: December 1999
Hilomen et al.[draft manuscript] Status of Philippine reef fish
INTRODUCTION
Reef fish communities constitute a major resource on reefs.
The levels of fishing
mortality on reef fishes, particularly in most developing countries, have reached dangerous
levels, with limit to “wild” marine fisheries catches reached many years ago (FAO 1994). This
has been particularly observed in reef areas near population centers in developing nations where
fish are often a main source of animal protein (Munro 1983, Alcala and Gomez 1985). In the
Philippines, reef fish contributes about 10-15% to the country’s total fishery (Carpenter 1977,
Murdy and Ferraris 1980). The high fisheries yield underscores the importance of this resource
to many of the coastal communities in the country. Yet there is very little information on the
status of this resource in the country. A baseline of information (e.g. inventory of resources) is
important in monitoring studies. Majority of the information on Philippine reef fish communities
pertain to distribution patterns (e.g. Hilomen and Gomez 1988, Aliño et al. 1993, Dantis et al.
1999), fisheries (e.g. Alcala 1981, Alcala and Luchavez 1981, Alcala and Gomez 1985, Alcala
and Russ 1990) and biodiversity (e.g. Aliño and Dantis 1999). To date, little has been published
on status of reef fish communities of the country on a nationwide scope.
The main objective of this study is to assess the condition of reef fish communities in the
Philippines.
Specifically, this study aims to provide quantitative data on species richness,
abundance, biomass and species composition of fish communities across reef areas in the
country. In addition, this study aims to formulate a relative measure using these community
parameters to determine conditions of reef fish communities in the country.
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Hilomen et al.[draft manuscript] Status of Philippine reef fish
METHODOLOGY
A subset of reef fish data stored at PhilReefs database was used in this study. The
PhilReefs database on fish was obtained using visual census (English et al. 1994) from several
completed projects by different institutions between 1986 and 1999 in various locations around
the Philippines (Table 1). Fish data with resolution to species level of identification, counts of
individuals and estimates of sizes were included in this study. This data set was largely obtained
by personnel trained at the Marine Science Institute (MSI) of the University of the Philippines
and included in this study based on uniformity of field methodology.
Briefly, fish visual census was conducted as follows. A 50-m line laid following depth
contours of a reef in each study site was used to examine species composition, number of
species, abundances, and biomass of associated reef fish. Census was made every 5 m interval.
All fish encountered within 5 m on either side and above the line were identified to species level
whenever possible, counted and their sizes (total length) estimated to the nearest cm (English et
al. 1994). Fish identification followed that of Randall et al. (1997) and FishBase (2000). Fish
biomass was calculated using the formula, W = a * Lb, where W is weight (g), a the
multiplicative factor, L the estimated length (cm) and b the exponent (b>1). The specific
constants a and b used in this study followed those from Kulbicki et al. (1993) and FishBase
(2000). In species where no constants exist, the known constants for the closest relative with the
same body shape were used.
The length of a sampling unit (transect) in the database varied between study sites. In
majority of the study sites, a transect sample consisted of three 50-m lines while 1 or 2 50-m
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Hilomen et al.[draft manuscript] Status of Philippine reef fish
lines were also common in many other sites. Regardless of the length of sampling unit, all data
from a total of 570 transects (402 in Luzon, 71 in Visayas and 97 in Mindanao) were included in
determining species distribution (i.e. presence/absence data). This represented more than 40% of
the database and covered more than 70% of the areas surveyed in the country. The locations of
study sites are presented in Figure 1. The study sites are distributed in 24 coastal provinces, 11
in Luzon, 9 in Mindanao and 4 in the Visayas.
In the analyses for species richness, abundance and biomass, 2 50-m line transects were
considered as a sampling unit to allow spatial comparison between and within sites. All study
sites with a single 50-m line transects were excluded in this level of analysis. In study sites
where 3 50-m line transects were laid, only data pooled from the first 2 lines were included in the
analyses.
Summaries of species richness, abundance and biomass for each transect were generated
and expressed in units of 1000 m2. A total of 539 transects were included in the analysis for
species richness, 504 for abundance and 227 for biomass.
Histograms from frequency
distributions of these parameters were used to determine ranges of very high, high, moderate,
poor and very poor categories. Data for abundance and biomass were log transformed.
RESULTS
A total of 915 species belonging to 63 families were recorded from 570 transects in
various study sites from 18 major locations in the country (Table 2). Nearly 30% of these
species were damselfishes (Pomacentridae, n=137) and wrasses (Labridae, n=136). The other
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Hilomen et al.[draft manuscript] Status of Philippine reef fish
most represented families include groupers, rock cods and fairy basslets (Serranidae, n=63),
butterflyfishes (Chaetodontidae, n=48), parrotfishes (Scaridae, n=46) and surgeonfishes
(Acanthuridae, n=42) (Table 2). The total number of lutjanid and lethrinid species recorded
countrywide was 26 and 12, respectively.
The total number of species exceeded 300 in 5 of 18 major locations (Table 2). This was
recorded in Puerto Galera, Oriental Mindoro (n=514), Palawan Shelf (n=462), Tubattaha Reefs
(n=374), Pangasinan (n=356) and Southwestern Mindanao (n=354) (Table 2). More than 200
species were recorded in 9 other locations and over 100 in the remaining 4 locations (Table 2).
The number of species of the six most speciose families mentioned above remained consistently
high for all locations and the same families dominated species composition of fish assemblages
in the area.
Species richness
Nearly 70% of transects examined (n=539) for species richness fell under the poor (27-47
species 1000 m-2) to moderate (48-74 species 1000 m-2) categories, while 5% were in the very
poor category (0-26 species 1000 m-2) (Table 3). Close to 20% of transects were under the high
category (75-100 species 1000 m-2) and only 5% were in the very high category (>100 species
1000 m-2).
Species richness of reef fish assemblage was high in Palawan Shelf, specifically the
Malampaya Sound and two locations in the Sulu Sea (i.e. Tubattaha Reefs and Turtle Islands)
(Figure 2). Species richness was moderate in majority of the reef areas in Luzon, northeast
Mindanao (Surigao) and southwest Mindanao (Tawi-tawi) (Figure 2). Poor species richness was
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Hilomen et al.[draft manuscript] Status of Philippine reef fish
recorded in Bolinao in Pangasinan, Ragay Gulf, Cebu, Zamboanga, Sarangani and Davao Gulf
(Figure 2).
Fish abundance
Fish abundance in 45% of transects examined (n=504) fell under the moderate category
(677-2267 individuals 1000 m-2) while 21 and 26% were under the poor (202-676 individuals
1000 m-2) and high (2268-7592 individuals 1000 m-2) categories, respectively (Table 4). Fish
density was very poor (0-201 individuals 1000 m-2) in 3% of transects and very high (>7592
individuals 1000 m-2) in nearly 5% (Table 4).
High fish abundances were observed in 7 locations in the country.
These were in
Batanes, Calauag Bay, Puerto Galera in Oriental Mindoro, Malampaya Sound in Palawan Shelf,
Tubattaha Reefs, Bais Bay in Negros and Surigao (northeast Mindanao) (Figure 3). Poor fish
abundances were observed in Bolinao in Pangasinan, Lagonoy Gulf, Zamboanga, Sarangani Bay
and Davao Gulf (Figure 3).
Fish biomass
Estimates of standing stock biomass ranged from 0.31 to over 220 mt-km-2. Seventy-six
percent of transects examined (n=227) fell under the low (5.1-20.0 mt-km-2) and very low (<5.0
mt-km-2) categories (Table 5). A little over 13% of transects were under the range of moderate
category (20.1-35.0 mt-km-2) and only about 11% were in the high (35.1-75.0 mt-km-2) to very
high (>75.0 mt-km-2) categories (Table 5).
Estimates of reef fish biomass were high to very high in only 2 reef areas of the country
(Figure 4). These areas were the Tubattaha Reefs and Malampaya Sound in northern Palawan.
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Hilomen et al.[draft manuscript] Status of Philippine reef fish
Biomass of reef fish in majority of the areas surveyed in the country ranged from low to very low
(Figure 4). Reef areas with very low fish biomass include Bolinao in Pangasinan, Aurora, Ragay
Gulf and Lagonoy Gulf in Bicol and Zamboanga. Reef areas with low biomass of reef fishes
include the Kalayan Island Group (KIG), northern Palawan, Davao Gulf, Sarangani, Tawi-tawi
and the Turtle Islands (Figure 4).
DISCUSSION
A major aim of this paper was to assess the status of reef fish communities in the
Philippines.
This study used community parameters such as species composition, species
richness, individual abundance and biomass to investigate the condition of reef fish assemblages
around the country. The high number of species listed (n=915) from all transects around the
country underscores the diversity of fish life on reefs of the country. The Philippines sits at the
northern tip of the triangle in the Indo-Pacific region considered to host the world’s greatest
number of marine animals (Sale 1991). The number of reef fish species obtained in the study
represents about 60% of the total reef associated species listed worldwide in FishBase (2000).
This number largely reflects only the diurnal and non-cryptic species observed during visual
census. To date, there is no complete inventory of reef fish in the country but the total number of
reef fish species is likely to exceed this listing.
The reef areas of Palawan, Sulu Sea and oldest reef formations in Mindoro (Puerto
Galera) are areas of richest species diversity for reef fish communities in the country. These
areas constitute about a quarter of all areas surveyed in the country. In contrast, species richness
of reef fish communities in majority of reef areas (about 70%) surveyed ranged from poor to
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Hilomen et al.[draft manuscript] Status of Philippine reef fish
moderate. Many of these areas are near coastal population centers and are heavily exploited (e.g.
Bolinao, Pangasinan, Ragay Gulf, Cebu, Zamboanga, Sarangani and Davao Gulf).
Generally, reef fish abundances in nearly half of the reefs surveyed are in moderate
condition while the same was high to very high in more than 30%. Reef areas with high to very
high abundance of reef fish appear to be fairly scattered over the country. A large proportion of
this total abundance comprised schooling damsels, labrids, basslets and fusiliers. These species
are small in size and are rarely targeted, except for the fusiliers. While these species are small,
they are ecologically important. They link the producers on reef to the large predators. The
abundance of large to medium predators is very low in many of the areas in the country.
Standing stock biomass of less than 20 mt-km-2 in more than 75% of reef areas surveyed
is very alarming. Many of these reef areas are easily accessible and represent near collapse
fisheries resources. Only a measly 11% of reef areas surveyed have biomass under the high to
very high categories. Many of these areas are currently under varying levels of protection, the
enforcement of which is highly dubious (e.g. areas declared as sanctuaries, reserves and
replenishment areas).
In reef areas with poor fish species richness, moderate fish abundance and very low fish
standing stock biomass the dominant forms are small benthic predators, small herbivores and
grazers. The rarity of large predator fish and the dominance of small benthic predators, small
herbivores and grazers in majority of the reef areas in the country suggest ecosystem overfishing
(Russ 1991). It is highly likely that the more desirable species have been heavily targeted. The
consistent removal of large predator fish on these areas is a clear example of how unabated
fishing results in changes in reef fish community structure to less desirable species combinations.
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Hilomen et al.[draft manuscript] Status of Philippine reef fish
This is consistent with findings of other studies. Koslow et al. (1988) found that 15 years of
increasing fishing effort reduced fish communities in the Pedro Cays, Jamaica dominated by
lutjanids and scarids to ones dominated by boxfishes, pufferfishes and squirrelfishes. Even a
short period of intense fishing (e.g. 18 months) drastically altered densities of more favored
species and significantly changed community structure of reef fishes (Russ and Alcala 1989).
Consistent heavy fishing pressure further exacerbates the poor situation of majority of
reefs in the country. Russ (1991) reported that yields from more recent studies ranged from 0.42
to 36.9 mt-km-2yr-1 and suggested that harvest of finfishes from intensively fished, small areas of
coral reef on the order of 10-20 mt-km-2yr-1 seem feasible. The results of this analysis suggest
that reef fisheries yields of 10-20 mt-km-2yr-1 are likely feasible in less than a tenth of the
remaining reefs in the country. Furthermore, only about 1.5-6 mt-km-2yr-1 of reef fisheries yield
will be feasible in the vast majority of reefs in the country assuming that only 30% standing
stock biomass are allowed harvested. Many experts caution that removing 30% of standing
stock annually is already a high level of fishing pressure (e.g. Munro 1983).
The slow
accumulation of biomass for most reef fish (long-lived and slow growing) makes them highly
vulnerable to this level of exploitation pressure. The estimates of standing stock biomass of reef
fish communities are dangerously very low in more 40% of Philippine reefs. The classic effects
of overfishing (Pauly 1988, Russ 1991) are increasingly observed in many of the reef areas
surveyed. Moreover, a steadily burgeoning population and widespread poverty exacerbate the
effects of overfishing. There are simply too many users and not enough resources. These factors
have led to a steadily increasing fishing effort such that reef fishery resources in majority of the
Philippine reefs are near collapse. In many situations, small-scale fishers resort to wholesale
resource destruction in an effort to maintain incomes without regard to future generations –
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Hilomen et al.[draft manuscript] Status of Philippine reef fish
tragedy of commons (Pauly 1988, Russ 1991). At best, reef fish communities in majority of reef
areas in the country have poor to moderate number of species and moderate to high abundances.
The species dominating most communities are undesirable but may be ecologically important.
Very few of the reefs surveyed have good to excellent reef fish communities.
The information on the status of reef fish communities in the country based on the 3
parameters show a bleak future if factors that lead to this decline is not checked. This declining
state of reef fisheries in the Philippines can be placed in check if fishing effort is drastically
reduced (e.g. McManus 1996) and novel approaches to coral reef fisheries management such as
the establishment of spatial reef refuges are installed (e.g. Bohnsack 1996, Russ 1996). Spatial
reef refuges (marine fishery reserves) may be one of the few management options available to
maintain levels of spawning stock biomass necessary to sustain reef fisheries (PDT 1990,
Bohnsack 1996, Russ and Alcala 1996, Russ 1996). A properly functioning marine reserve
serves as insurance to fishery management failures.
There is an urgent need to protect the few remaining reef areas (Palawan, Tubbataha
reefs, Turtle Islands) of high diversity, high abundance and high biomass to serve as insurance
for the future and as benchmarks for determining changes in fish communities.
Equally
important is the need to understand better the ecological processes that render these ecosystems
productive and population dynamics that ensure constant replenishment of stocks.
Acknowledgement: We wish to acknowledge the support provided by the Packard Foundation
to review the status of reef fish communities in the country. Our sincere thanks go to PhilReefs,
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Dr. Edgardo D. Gomez, Dr. Wilfredo Licuanan, Dr. Porfirio M. Aliño and the various research
projects under UP-MSI, DA-BFAR, DA-BAR and DENR.
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