Spatial and temporal dynamics of sea surface
temperature and chlorophyll-a in Makassar Strait
observed from satellite images: oceanographic
characteristics identifying fish distribution and
abundance
Mukti Zainuddin
Faculty of Marine Science and Fisheries
Hasanuddin University
Abstract
To describe spatial and temporal dynamics of sea surface temperature (SST) and chlorophylla concentration (Chl-a) and to identify the predicted area of fish distribution and migration in
Makassar Strait, monthly mean remotely sensed satellite data in 2009 were used. Results
showed that SST and Chl-a have different spatial and temporal patterns along Makassar Strait.
SST tended to be high during the first transition season (March-May) and reached a peak in
April at the level of approximately 30°C especially in southern area. Whilst, Chl-a appeared
to be high during the west season (January-March) in the central and south of Makassar Strait.
During that period, Chl-a ranged from 0.5 to1.0 mg m-3. The Chl-a started to significantly
decrease in April and then tended to be constant through December. Most of potential
predicted areas for pelagic fish such as for skipjack and mackerel in Makassar Strait
developed in the southern area along South Sulawesi waters when progression of warm
waters SST moved from southern area to the north from April to July. At the same time and
location, Chl-a concentrations tended to gradually well enhance. As a result, skipjack tuna
and mackerel were clearly identified to have the high probability of finding the fish in the
southern area both December and in March. It suggests that satellite images provide a
powerful tool to identify spatial and temporal fish distribution and abundance throughout a
year in Makassar Strait.
Keywords: SST, Chl-a, satellite images, predicted area, fish distribution and abundance
INTRODUCTION
Marine fishery resources rely on specific oceanographic structures for feeding, reproduction,
and migration and the link between the availability of potential fishing location and fish
population dynamics is widely documented in the coastal environment (Laurs, 1984; Inagake
et al., 2001). In the tropical coastal environment, spatial and temporal dynamics of
oceanographic conditions such sea surface temperature (SST) and Chl-a concentrations play
an essential role for identifying pelagic fish distribution and abundance (Zainuddin, 2009;
Zainudin and Jamal, 2009). A fruitful approach to understanding the impact of the two
oceanographic signatures on pelagic ecosystem dynamics may be to understand the impact of
environmental variability on key habitats.
From historical point of view, satellite remote sensing has proved an important source
of information to marine science and fisheries oceanography research. SST and Chl-a
concentrations are important oceanic parameters in explaining the dynamics of pelagic
fishing ground. Thermal features of sea surface provide reliable proxy indicators of the
spatial and temporal distribution of prey abundance, which subsequently affects tuna
distribution (Humston et al., 2000). Ocean color feature is a good indicator of seasonal
variations of chlorophyll fronts (TZCF), which are linked to tuna forage habitat (Polovina et
al., 2001).
Makassar Strait is one of the most productive fishing grounds in the eastern part of
Indonesia. This area is one of the primary pathways of Indonesian throughflow (ITF) from
North Pacific which has an estimates of total volume transport of water-mass distribution at
approximately 8-9 Sv (one Sv / Sverdrup, is an ocean transport unit, equal to a current of one
million cubic meter per second) (Gordon, 2005). The ITF influences oceanographic
structures in the strait. Dynamics of oceanographic parameters such SST and Chl-a within
Makassar Strait is very important for pelagic fish distribution, migration pattern and
abundance.
Since 2002, Aqua satellite sensor, Moderate-resolution imaging spectrometer
(MODIS) has provided high spatial and temporal resolution of SST and Chl-a that has proved
the key to recent studies on physical-biological links (Druon, 2010). This paper will use the
SST and Chl-a data derived by remote-sensing to focus on the spatial and temporal dynamics
of the oceanographic conditions in Makassar Strait. The objectives are to describe spatial and
temporal dynamics of SST and Chl-a and to identify the predicted area of fish distribution
and migration in Makassar Strait.
DATA AND METHODS
The physical and biological environmental data used to describe the dynamics of
oceanographic conditions in Makassar Strait during January-December 2009 were SST and
Chl-a data derived from Aqua/MODIS. The NASA distributes Standad Mapped Image (SMI)
level 3 binary data with HDF (Hierarchical Data Format) format (http:
oceancolor.gsfc.nasa.gov). This study used the satellite data with monthly temporal resolution
and 0.044° of longitude and latitude spatial resolution. .This study divided the study area into
three groups: (1) north of Makassar Strait: 1 N- 1 S and 117.5-120 E; (2) central area: 1-3.5 S
and 117-119.5 E; and (3) south of Makassar Strait: 3.5-5.5 S and 117-119.5 E. All SST and
Chl-a values for all pixels on each group were extracted to calculate the trend of monthly
mean variables from January to December 2009.
To identify the predicted area of fish distribution and abundance in Makassar Strait,
potential fishing location map was constructed from the significant and favorable ranges of
the two environmental variables (SST and Chl-a). Preferred SST and Chl-a for skipjack and
mackerel were based on previous study (Zainuddin et al., 2008; Zainuddin and Jamal; 2009).
The map consisted of binary output in which the black color represents non preferred area,
and the white one denotes the high probability area of finding pelagic fish (skipjack and
mackerel). This study used these species as examples since they are the main target for
commercial fisheries in Makassar Strait. The potential fishing ground map was computed by
combining the three favorable oceanographic conditions of satellite images (significant
variables) into a single map with the same spatial and temporal scale for each grid satellite
data using the Interactive Data Language (IDL 6.3) software package. All data processing
and mapping in this paper were made using the software package.
RESULTS
1. Spatial Distribution of Sea Surface Temperature (SST)
Spatial distributions of monthly mean SST estimated from satellite data showed that cold
surface water in Makassar Strait occurred during January-February 2009 (Fig.1). The
relatively low SSTs were mainly found in the central and southern Makassar Strait during the
period. Warm water SST started from the southern area in April with the SST level of more
than 30°C and move to the north through July and then the SST tended to decrease from
August to November. In the southern area, the lowest SSTs appeared in August around
Takalar coastal waters and the SST gradually increased till December.
Fig. 1. Remotely sensed sea surface temperature estimated from Aqua/MODIS for the
Makassar Strait from January to December 2009.
Figure 2 showed that the lowest temperature in Makassar Strait occurred during the
west season (December-February) in the central and south of the strait. The SST level in the
period was less than 28°C on average. The highest SST occurred in the first transition season
particularly in the southern area of the strait with the SST of more than 30°C. The average
SST in that period was about 29°C. During the east season, SST was highest (>30°C) in the
central and northern side of Makassar Strait especially near Celebes (Sulawesi) island.
However, the lowest SSTs were encountered in the south of South Sulawesi Province with
the level of less than 28°C SST . The surface temperature tended to be stable (less variability)
during the second transition season.
Fig. 2. Remotely sensed sea surface temperature estimated from Aqua/MODIS for the
Makassar Strait for all seasons (west season, first transition season, east season and second
transition season) in 2009.
2. Spatial Distribution of Chl-a
The Chl-a concentration tended to high from January to March in eastern and southern part of
Makassar Strait (Fig.3). In these areas, Chl-a density were mostly greater than 0.5 mg m-3.
The highest Chl-a was found in eastern area closed to Borneo Island with the density of more
than 0.84 mg m-3. From April to December, the Chl-a appeared to be constant. It is
interesting to note that in August 2009, the high Chl-a concentrations were observed along
Takalar, Jeneponto and Bantaeng coastal waters.
Fig. 3. Remotely sensed surface chlorophyll density estimated from Aqua/MODIS ocean
color for the Makassar Strait from January to December 2009.
Figure 4 showed that Chl-a concentrations were consistently high in eastern side of
Makassar Strait for all seasons in 2009. The Chl-a densities in that area were observed to be
greater than 0.84 mg m-3. The greatest Chl-a were found during the west season. Chl-a
concentrations were lowest in the second transition season along the center of Makassar Strait.
The relatively low Chl-a densities in that area were about less than 0.18 mg m-3. The
relatively high Chl-a concentrations along the coastal area of South Sulawesi Province can be
found in the east season, particularly in Takalar coastal waters.
Fig. 4. Remotely sensed Chl-a estimated from Aqua/MODIS for the Makassar Strait for all
seasons (west, first transition, east and second transition season) in 2009.
3. Temporal Variability of SST and Chl-a
It is important to point out that in Makassar Strait, the temporal variability of SST appeared
to be more fluctuated than that of Chl-a (Fig.5: left). A high variability of SST occurred
during January-February. SSTs tended to be high in the first transition season and reached a
peak in April in which the SST level was approximately 30°C especially in southern
Makassar Strait. From May to November, the trend of SST appeared to decrease. Although
the increased SST can be seen in December in the south of Makassar Strait, but the lowest
SST can be clearly found in January where the SST level was about 27°C. Figure 5 showed
that the southern area of Makassar Strait had a highly SST variation compared with the other
areas. The northern area was less variable SST spatial pattern.
The Chl-a concentrations have different temporal variability with the SST (Fig.5:
right). All three areas in Makassar Strait have similar Chl-a trend along the year of 2009.
Chl-a tended to increase in the west season especially in January where the density levels
ranged from 0.5 to 1.0 mg m-3. In general, the level of Chl-a concentrations seem to be stable
from April to December. For all areas along the strait, the Chl-a densities during that period
were about 0.5 mg m-3 on average. The Chl-a appeared to slightly increase only in July. In
the northern Makassar Strait, the Chl-a concentrations were much more variable than both in
central and southern area.
Fig. 5. Temporal variability of monthly mean SST (left panel) and Chl-a (right panel) with ±
1 standard deviation estimated from Aqua/MODIS in the Makassar Strait for JanuaryDecember in 2009.
4. Predicted Area of Fish Distribution and Abundance
Figure 6 indicated that spatial pattern of preferred oceanographic conditions for skipjack and
mackerel was considerably different. Skipjack tended to inhabit the specific area of
Makassar Strait both in March and in December. Whilst, mackerel appeared to occupy a wide
area of the Strait in same period. In March, skipjack tuna were predicted to occur along the
north and center of Makassar Strait closed to the Sulawesi coast. It seems different in
December where skipjack tended to concentrate in the southern area. Predicted area for
mackerel were more developed in northern and southernmost Makassar Strait in March.
Meanwhile, in December the high probability areas of finding mackerel were mostly in
central and southern Makassar Strait particularly along the coastal of South Sulawesi
Province.
Fig. 6. Spatial distribution of predicted area for skipjack (left) and mackerel (right) along
Makassar Strait in March (top) and December (bottom) 2009.
DISCUSSION
With just a year of high resolution remote sensing datasets, it is already apparent that spatial
and temporal dynamics of the SST and Chl-a could be observed. A description of these
oceanographic parameters is very important to understand spatial and temporal patterns of
pelagic fish distribution and abundance. It is important to note, however, that the predicted
areas are just proxies indicating the high probability locations of finding fish. The prediction
map is based on the joint preferred environmental ranges for a certain species, so that the
accuracy of the prediction is strongly dependent on the quality and quantity satellite basedoceanographic datasets and knowledge about fisheries oceanography and ecology for each
species. Therefore, this study could be as preliminary nature of results in providing insight
into identification of potential pelagic fishing ground.
During 2009, the spatial and temporal patterns of SST are different with those of Chla. It is probably that both these oceanographic parameters influence concurrently to the
spatial pelagic fish distribution and abundance. Most of potential predicted areas in Makassar
Strait such as for skipjack and mackerel develop in the southern area (South Sulawesi waters)
when progression of warm waters SST moves from south to the north from April to July
(Figs. 1 and 2). At the same time and location, Chl-a concentrations tended to gradually well
enhance (Figs 3 and 4). As a result, during this period (first transition-east seasons), many
pelagic species distribute and associate with oceanographic structures existing in this area
including skipjack and mackerel (Zainuddin et al., 2008; Zainuddin, 2009). This phase was
well identified where the SST and Chl-a were more than 28.5°C and about 0.25 mg m-3,
respectively.
The prediction map also indicates that the most potential fishing grounds in Makassar
Strait occur in the southern area (Fig. 6). Both in March and December, the predicted areas
are well formed for skipjack and mackerel within the area of south of Makassar Strait. It is
most likely that the availability of upwelling and frontal zones strongly supports a highly
productive habitat in that area (Ilahude, 1971; Zainuddin, 2009). The understanding of spatial
and temporal SST and Chl-a is very useful to identify high productive fishing locations
including upwelling and frontal zones particularly along Makassar Strait.
CONCLUSIONS
The spatial and temporal dynamics of SST and Chl-a are very important to understand the
preferred area of fish concentration and distribution in Makassar Strait. The space-time
patterns of the oceanographic conditions during 2009 are different, but complement one
another to create potential fishing grounds. The most potential predicted area for fish
distribution and abundance occur in the southern area of Makassar Strait (South Sulawesi
coastal waters). This area mainly develops from April to July in which most pelagic species
well associate.
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