Figure 1.6. Relative abundance of reef associated fishes

The study site for the reef
survey is illustrated in
figure 1.1. It is situated at
_insert coordinates here_
of Batangas City near the
JG Summit Petrochemical
Corporation. It is a noncontiguous patch of reef
along the coastal area. It is
near a land reclamation of
a once mangrove area
north of the station.
Fish Visual Census (FVC) is a
estimates the density,
richness of reef associated
fishes in their habitat. For
this study, three 5m bands
with the length of 30
meters were positioned
and surveyed along the
reef crest. Fishes were
identified, until the species
Boundary of Simlong
level whenever possible
Coral Reef Station
through the use of
photographic field identification guides. Their count and sizes (to the nearest centimeter) were also
estimated to serve as basis for the computation of their abundance and biomass. Biomass was
computed using the formula:
π΅π‘–π‘œπ‘šπ‘Žπ‘ π‘  = (
π‘Ž × π‘ π‘–π‘§π‘’
) × π‘π‘œπ‘’π‘›π‘‘
where a and b are species-specific growth constants derived from length-weight relationships of each
species of fishes.
Each fish were then categorized according to their family, functional group and their commercial and
ecological importance. Graphical representations were generated to illustrate the relative abundance
and biomass of each category.
Biological indices were computed to estimate the level of diversity, dominance and species richness of
the representative fish species. The formula for the Shannon Index of Diversity (H’) is as follows:
 ni οƒΆ
 ni οƒΆοƒΉ
H ' ο€½ ο€­οƒ₯ οƒͺ οƒ· ο‚΄ ln  οƒ·οƒΊ
 N 
i ο€½1  N οƒΈ
where ni represents the total abundance of each species of fishes while N is the total number of fishes
surveyed. The value for H’ ranges from 0-4 where 4 indicate the highest level of diversity.
Another is the Simpson’s Index of Biodiversity (D) which has the formula:
οƒ₯ ni ο‚΄ ni ο€­ 1
N ο‚΄ N ο€­ 1
where ni represents the total abundance of each species of fishes while N is the total number of fishes
surveyed. The value of D ranges from 0-1, where, as the value decreases the level of diversity increases.
The inverse of the Simpson’s Index of Diversity (1-D) measures the level of dominance in a habitat, also
known as the Simpson’s Index of Dominance (SID). As the value of SID increases, dominance in the
habitat decreases.
Peilou’s Index of Evenness (J’) describes the relative abundance of species. It is a function of the
abundance of species and the species richness in the habitat. It is represented by the formula:
𝐽′ =
1 1
𝐻′π‘šπ‘Žπ‘₯ = − ∑ 𝑙𝑛
where S is the value of the Species Richness which is simply the total number of species present in the
habitat. The value of J’ ranges from 0-1, where, as the value approaches 1, species in the habitat
becomes more evenly distributed.
Results and Discussion
The total estimated abundance of reef associated fishes at the sampling station was 1,303 individuals/
900m2 which were represented by 80 species. Species under Apogonidae or cardinalfishes had the
highest representation in terms of count with 47% of the total estimated abundance of reef fishes. This
was followed by the pomacentrids or the damselfishes with 35% of the total estimated abundance as
seen in Figure 1.2.
Other Families
Figure 1.2. Relative abundance of reef associated fishes categorized
according to family.
The total estimated biomass of the cardinal fishes (Apogonidae) was the highest in the survey station
with 29% (4.36 kg/ 900m2) of the total biomass, this was followed by the pomacentrids with 25% and
the wrasses with 14% (Figure 1.3).
The most abundant fish species observed in the station was the Dusky-tailed Cardinalfish (Archamia
macroptera) which was at around 350 individuals/ 900m2. This species is usually found in the Indo-West
Pacific and said to aggregate among branching corals, inhabiting lagoons and fringing coral and rocky
reefs with sand and rubble bottom in relatively clear water (FishBase, 2004).
Among the damselfishes (Pomacentridae), the Charcoal damsel (Pomacentrus brachialis) was the most
abundant in the sampling station with 105 individuals/ 900m2. These are non-migratory species that
thrive in depths of around 6-40 meters. Their adult forms are found in outer reef slopes and occur singly
or in small groups. They pair up during breeding and their eggs remain demersal and adhere to the
substrate (FishBase, 2004).
Labrids or wrasses (Labridae) were mainly represented by the Moon wrasse or Thalassoma lunare with
23 individuals/ 900m2. They are solitary or occur in groups at the upper portions of the coral reef. They
feed on small benthic invertebrates and fish eggs. They are reported to be protogynous hermaphrodites
or animals that are born male and shifts to female through sex reversal (FishBase, 2004).
Other Families
Figure 1.3. Relative biomass of reef associated fishes categorized
according to family.
As biomass is a function of count, size and height-weight constants of the fish species, it is observed that
the percentage of biomass does not necessarily follow that of the abundance for some species can be
larger than the others. This is why even though Chaetodontidae, which are usually bigger than
cardinalfishes and damselfishes, was only represented by 7 observed individuals; it managed to weigh
10% of the total estimated biomass.
Figure 1.4. Relative abundance of reef associated fishes
categorized according to functional groups.
In terms of the relative composition of the functional groups, benthic carnivores were the most
represented with 59% or 764 individuals/ 900m2 of the total fish surveyed followed by omnivores and
herbivores with 19% and 12%, respectively (Figure 1.4).
Figure 1.5. Relative biomass of reef associated fishes categorized
according to functional groups.
The benthic carnivores such as Apogon macroptera (Dusky-tailed Cardinalfish) and Halichoeres
hortulanus (Checkerboard Wrasse) had the highest commulative biomass of 57% or about 8.5 kg/ 900m2
followed by the omnivores and the planktivores with 19% and 9%, respectively (Figure 1.5). These values
show that the benthic community surveyed in the reef stations probably caters more food items and
habitat opportunity for the benthic carnivores as compared to the other functional groups.
Benthic carnivores are species of fishes that feed upon macro-invertebrates that inhabit the reef’s
substrate. These include benthic crustaceans, amphipods, polychaetes, molluscs, sponges, tunicates,
shellfishes, echinoderms, and many more. Omnivores on the other hand are more generalist feeders.
They prey on invertebrates, algae and even detritus in the reef. Planktivores are usually found in mid
water feeding on phytoplankton and zooplankton.
In terms of their habitat preference, as they may all have close association to the reef, planktivores have
larger home ranges as compared to benthic carnivores and omnivores for their prey are loosely
associated to the benthic environment and tend to concentrate in mid-waters.
Figure 1.6. Relative abundance of reef associated fishes categorized
according to ecological and economic importance.
Figure 1.6 is a graphical representation of the proportions of the total estimated abundance of reef
associated fished categorized according to their economic and ecological importance. This followed the
importance and diet information from FishBase 2004. The categories are as follows: “indicator’, “major’
and “target” species. Indicator species are mostly coral-feeding fishes known to have close association
with the benthic environment, more specifically, with live corals. Their presence and abundance in an
area is indicative of the relative state of that reef (Crosby and Reese, 1996). They are mainly represented
by butterflyfishes and angelfishes. Target species, on the other hand are those species with commercial
importance or those that are harvested in fisheries. They can be high-value species such as groupers,
snappers and jacks, or those that are targeted for aquarium fisheries such as clownfishes, damselfishes
and lionfishes. Major species are ecologically important species that hold unique niches and function as
important trophic links. These fishes are often the most numerous and conspicuous on reefs, and
include most species of damselfishes, wrasses, and anthias, among others (Samaniego, 2013).
Figure 1.7. Relative biomass of reef associated fishes categorized
according to ecological and economic importance.
Major species such as that of the cardinalfishes and damselfishes were the most abundant (1,204
individuals/ 900m2) and had the highest cumulative biomass (11.75 kg/ 900m2) relative to the other
groups as shown in Figures 1.6-7. This was followed by the target species represented by the
nemipterids, acanthurids and caesionids (breams, surgeonfishes, and fusiliers, respectively) with 6% of
the total estimated abundance and 14% of the total estimated biomass. Indicator species, which are
mainly butterflyfishes (Chaetodontidae) was rather scarce in the area with only 2% of the total
estimated abundance and 6% of the total estimated biomass.
The abundance and biomass of the target and indicator species, which are consequently the
economically and ecologically important species, are relatively low which can be a basis of saying that
the status of the fish community in the area is poor. This can be attributed to the level of fisheries in the
study site and the state of its benthic environment.
Table 1.1. Diversity indices of the reef associated fishes surveyed in Simlong,
Batangas City, Batangas.
Margalef's Species Richness (S)
Shanon's Index of Diversity (H')
Simpson's Index of Diversity (D)
Simpson's Index of Dominance (SID)
Pielou’s Index of Evenness (J')
The diversity of the reef associated fishes in the marine study area was measured using various diversity
indices (Table 1.1). Margalef’s Species Richness, which is the total number of species present in the reef,
had a value of 80 species/ 900m2. The value for the Shanon’s Index of Diversity, which usually ranges
from 0-4, was 3. This is relatively high and reflected high variety of species in the study area.
Another index used was the Simpson’s Index of Diversity which ranges from 0-1; where, as the value
reaches 1 diversity decreases. The value computed for the fish diversity in the study site was 0.102
which indicates high diversity of fish species and verifies the result of the Shanon’s Index of Diversity.
The advantage of having high diversity in a certain habitat is that there is more variety of fishes that
could represent different trophic levels. The community benefits from high diversity because there is
higher probability that all niches will be filled and are theoretically less likely to be invaded by
opportunistic introduced species. Another is that high diversity could mean long survivorship because of
the variety of genetic material they possess.
The Simpson’s Index of Dominance, which is an inverse function of the Index of Diversity, was computed
to have a value of 0.898. This index also ranges from 0-1 and as the value increase, dominance decrease.
Having a low level of dominance is advantageous in any habitat because in an area with low dominance,
there is less chance of local extinction of species. An area with high dominance is more prone to mass
infection of diseases or infestation of parasites. But, on the other hand, lower level of dominance could
mean fragmentation of the habitat that was caused by natural or anthropogenic degradation.
The Pielou’s Index of Evenness measures how close in numbers each species are in an environment. It is
a diversity index that quantifies how equal the community is numerically. The value of this index ranges
from 0-1 and as it increases, the less is the level of evenness of the species becomes. For this study, the
level of evenness is high with 0.122. This goes to show that the representative fishes are relatively
evenly distributed amongst species. This is a reflection of the low dominance and the high diversity of
the fish species in the study area.
References and Appendices
To follow. 