The Determination of Shortfin Scad (Decapterus sp ... · Most of the fish landed at PPN Pekalongan...

Available online at www.worldscientificnews.com

( Received 10 January 2019; Accepted 26 January 2019; Date of Publication 27 January 2019 )

WSN 119 (2019) 111-124 EISSN 2392-2192

The Determination of Shortfin Scad (Decapterus sp.) Potential Fishing Area with Chlorophyll-a

Distribution in Pekalongan Sea, Central Java, Indonesia

Viga Ananda Wicaksono*, Zahidah Hasan, Iwang Gumilar, Lantun P. Dewanti

Faculty of Fisheries and Marine Sciences, Universitas Padjadjaran, Indonesia

*E-mail address: [email protected]

ABSTRACT

The fishing ground can be determined by detecting oceanography parameters in seawater area.

One of the oceanographic parameters that can be used is chlorophyll-a. This research aims to analyze

the relationship between chlorophyll-a and total catch of shortfin scad along with potential map areas

for fishing shortfin scad (Decapterus sp.) in Pekalongan seawater. The research was conducted in two

stages, which are field data collection in January and downloading and processing satellite image data

in February. This research used the survey method with spatial analysis. Primary spatial data used is the

distribution of chlorophyll-a and data of shortfin scad fishing production. The study shows an average

concentration of chlorophyll-a from 2013-2017 in Pekalongan seawater ranges around 0,16 - 1,55

mg/m3. The result of linear regression test shows that chlorophyll-a has a role as one of the factors that

influence the total catch of shortfin scad in Pekalongan seawater, East Java by 23%. Other factors

influence the remaining 77%. Based on the assessment of fishing ground, there are 25 potential

coordinate points of shortfin scad fishing area in Pekalongan seawater that can be categorized as a

potential fishing ground.

Keywords: Chlorophyll-a, Fishing ground, Pekalongan, Shortfin Scad

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World Scientific News 119 (2019) 111-124

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1. INTRODUCTION

Pekalongan city is one of the regions in Central Java which is known by enormous

potency in the field marine fisheries. Pekalongan City has a national fishing port (PPN) located

in the northern part, which is the biggest port and various resources of catching fish in Central

Java. Most of the fish landed at PPN Pekalongan are small pelagic fish, including selar fish,

tembang fish, and lemuru fish. Shortfin Scad (Decapterus sp.) grouped as small pelagic fish.

The production of shortfin scad in 2013 was about 3,704 tons, a decrease from 2012 production

approximately 4,306 tons (PPN Pekalongan Annual Report 2014, Prasetyo, 2018).

Production in fishing management is correlated with the fishing results. Fishing

optimization can be obtained with information about the fishing ground. Information on the

fishing ground can be identified through oceanographic parameters. Oceanographic parameters

are factors that have sufficient influence on the variability of the catch, especially for the pelagic

fish. As for the many oceanographic parameters that influence the determination of fishing

areas, one of them is chlorophyll-a (Apriliani et al. 2018, Chen, 2008; Rizal, 2019).

The problem faced in the effort to utilize marine fisheries resources is the difficulty in

determining potential areas for fishing. In general, fishers traditionally determine fishing areas,

for instance, based on their experience and presentiment. It would cause decreasing of

efficiency with the amount of time, cost and energy wasted. The proper and effective

technology is needed to overcome this problem. Application of the technology in estimating

potential capture areas can be done by detecting oceanographic parameters, such as chlorophyll,

sea surface temperature, thermal front and upwelling (Oguz et al. 2002).

One example of the remote sensing satellites for determining oceanographic parameters

is the Aqua moderate resolution imaging spectroradiometer MODIS satellite. The Aqua-

MODIS satellite can function in detecting chlorophyll-a in an ocean. Remote sensing with

satellites is an alternative because it can detect chlorophyll-a in a large area at one time with

operational costs that are relatively cheaper when it is compared to measuring data directly

(Reynolds et al. 2009).

This research aims to analyze the relationship between chlorophyll-a and total catch of

shortfin scad along with potential map areas for fishing shortfin scad (Decapterus sp.) in

Pekalongan seawater. Reviewed of the related literature reveals that satellite-derived

information has been used in mapping potential fish zones and marine applications, such as use

of the technology for ocean parameter extraction (William et al. 2007, Zine et al. 2008), and

use of SeaWiFS for mapping potential fish zones (Copeland et al. 2011, Montres et al. 2008).

Therefore, it is essential to determine the potential areas of shortfin scad catch based on the

distribution of chlorophyll-a as the necessary data for fishing activities in Pekalongan waters,

Central Java.

2. MATERIALS AND METHOD

The study was conducted in two stages. The first stage was collecting field data, taken

place at the PPN Pekalongan, Central Java, which was held in January 2018 and the second step

was downloading and processing satellite image data that carried out in February 2018.


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Figure 1. The research site map

The survey method used a spatial and temporal analysis of the shortfin scad production

and chlorophyll-a concentration monthly in a five years periods (2013 – 2017). This research

also used chlorophyll-a satellite image data, downloaded from the NASA database, and shortfin

scad production from fishing base PPN Pekalongan respectively. Furthermore, the obtained

data were analyzed using software, namely SeaDAS and ArcGIS, and horizontal maps as a

result.

The first stage carried out in this research was making a map of the research area using

ArcGIS 10.3, then downloading data on chlorophyll-a. Chlorophyll-a data was downloaded

from the www.oceancolor.gsfc.nasa.gov page in the .nc format and converted to .xls or .txt

files. Data on shortfin scad catches were obtained from PPN Pekalongan as well as interviews

with fishers carrying out fishing activities using fishing gear called mini purse seine.

The second stage was the image processing phase, with chlorophyll-a distribution data

that has been downloaded, then opened SeaDAS software to process the cropping area to be

used. It is essential to change the data that has been cropped so it can be read by ArcGIS

software and filter data that does not exist, the advanced data processing was done in Ms. Excel,

and then the data interpolation process was done in ArcGIS software to determine the

distribution of chlorophyll-a in Pekalongan seawaters.

The final stage was the processing of shortfin scad production data. Data of shortfin scad

obtained from PPN Pekalongan was processed into graphical form, where the data was


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validated by conducting interviews with fishers. Data from the fishing activities that had been

obtained are then analyzed and assessed based on predetermined indicators.

Ms. Excel 2016 was used to determine the relationship between production and

chlorophyll-a indicator. The degree of relationship is expressed by the correlation coefficient

(r). The higher “r” value indicates that the relationship between the two coefficients is getting

closer. The range of correlation coefficient values is -1 ≤ r ≤ +1. The correlation is strong if r ≥

0.7 and r ≤ - 0.7, and the correlation is weak if -0.7 < r < 0.7.

Furthermore, The determination of potential fishing area was based on two indicators,

encompass the production number of fish catches and the distribution of chlorophyll-a in the

fishing area. According to Bukhari (2014), the scoring method was used to assess the results of

the two indicators. The scoring method is shown in the table below.

Table 1. Potential Fishing Area Scoring Method

Coordinate

Potential Fishing Area Indicator

Potential Fishing

Area Score Production

(kg)

Chlorophyll-a

(mg/m3)

1.

2.

...

High (n = 5) High (n = 5)

Potential (n > 6) Moderate (n = 3) Moderate (n = 3)

Low (n = 1) Low (n = 1)

Source: Bukhari (2014)

3. RESULT

3. 1. Chlorophyll-a Concentration in Pekalongan Seawaters

Distribution extraction of Aqua-MODIS satellite images from 2013 to 2017 results in

varying chlorophyll-a concentrations around Pekalongan seawaters. The five year chlorophyll-

a concentration variation was used as an indicator of aquatic trophic state in the potential fishing

area.

The research location is at coordinates 5º00'00” S – 109º00'00" E and 6º38'20" S -

110º25'18" E. According to the results of the chlorophyll-a distribution map, a black box marks

the fishing ground in Pekalongan waters. The coordinate data obtained from fisherman logbook

at PPN Pekalongan, Central Java. The distribution of chlorophyll-a concentrations in

Pekalongan waters is shown in Figure 2.

In general, chlorophyll-a concentrations around the study sites range from 0.16 - 1.55

mg/m3. The range of chlorophyll-a concentrations in Pekalongan waters for five years (2013-

2017) showed in the table below.


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(a) 2013

(b) 2014


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(c) 2015

(d) 2016


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(e) 2017

Figure 2(a-e). Chlorophyll-a Distribution Map (2013–2017)

Table 2. The Lowest and Highest Chlorophyll-a Concentration in Pekalongan Waters

Years Lowest (mg / m3) Highest (mg / m3)

2013 0.19 1.52

2014 0.21 1.51

2015 0.17 1.53

2016 0.16 1.52

2017 0.21 1.55

Based on the data obtained in Table 2, the chlorophyll-a concentration in Pekalongan

seawaters can be categorized as an area that has high chlorophyll-a concentrations. According

to Nontji (1984), the chlorophyll-a concentration is high if the chlorophyll-a concentration is

more than 1 mg / m3. Data on the distribution of chlorophyll-a concentrations presented in

Figure 1 also shows that the closer to the coastal area, the higher the chlorophyll-a


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concentration. The high concentration of chlorophyll-a is influenced by the increase of nutrients

in the surface layer of the water through various processes of water mass dynamics, including

upwelling, vertical mixing of water masses and patterns of movement of water masses, which

carry nutrient-rich water masses from the surrounding waters.

The high concentration of chlorophyll-a around the coast occurs due to the accumulation

of nutrients carried by the river flow to the marine waters in the coastal region. It is following

by Nababan's statement (2009), which states that the supply of nutrients causes the high

distribution of chlorophyll-a through runoff land and increased rainfall.

3. 2. Shortfin Scad Production

The most dominant catch which is landed at the PPN Pekalongan, Central Java is shortfin

scad. Generally, shortfin scad is caught in various seasons, especially during the western season.

The production of shortfin scad during the period of 2013 - 2017 showed that there were

different fluctuations even though they tend to be stable, but there were decreases in 2015 and

2017. The shortfin scad catches for the period 2013 - 2017 are shown in Figure 3.

Figure 3. The production of shortfin scad in five years (2013-2017)

The highest monthly shortfin scad catch was in March 2016 amounting to 311,591 kg,

while the lowest catch was in July 2015 of 420 kg. The average shortfin scad catch for five

years is 897,428 kg, with an average monthly of 75,286 kg. The decline in total production

occurred in 2015 and 2017 due to the adverse effects of the weather and the number of trips per

year which decreased from the previous year.

Based on monthly catch data, it is known that the average shortfin scad catch decreases in June

- August each year. The decrease in catch is due to an alleviated number of boat trips compared

to other months. Otherwise, Perissi (2017) states that other factors must be considered to

0

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2013 2014 2015 2016 2017

Sho

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cad

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kg)

Jan

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Apr

Mei

Jun

Jul

Agt

Sep

Okt

Nov

Des


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declining issues, such as overexploited resources and lack of fishing management. The average

graph of monthly catches of shortfin scad for five years is shown in Figure 4.

Figure 4. Average monthly of shortfin scad catch results (2013-2017)

Results of average shortfin scad for five years in PPN Pekalongan indicate that catch

production shortfin scad is more significant in the west monsoon compared to the east monsoon.

Generally, in Indonesia, the fishing season is divided into west monsoon (September-February)

and east monsoon (March-August). Alleged fishing activities in the western season are more

trips made so that the production value is higher than the east season.

Marine productivity in Java sea also related to the monsoon wind. Chlorophyll-a and Sea

Surface Temperature experience mixing process which is affected by the speed of monsoon

wind. The faster wind speed, the stronger process mixing process occurred. The stronger mixing

process can carry more nutrients from deeper water which make chlorophyll-a increased.

(Wirasatriya et al. 2018).

3. 3. Correlation between Chlorophyll-a and Shortfin Scad Production

The relationship between chlorophyll-a and shortfin scad production in Pekalongan

seawaters is illustrated in Figure 5. The bar axis shows production, while the line axis represents

chlorophyll-a respectively in a five years periods (2013 – 2017).

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121 227

158 835

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Cat

ch R

esult

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Months


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(a) 2013

(b) 2014

(c) 2015

(d) 2016

(e) 2017

Figure 5. The Relationship between chlorophyll-a and shortfin scad production (2013 – 2015)

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The relationship between time lag chlorophyll-a concentration and shortfin scad

production in Pekalongan seawaters was obtained through statistical analysis using software

ms. Excel. The results of the linear regression test show that the value of R square (R2) is 0.23

or 23%. Based on these values, it can be overviewed that 23% of the chlorophyll-a factor affects

the shortfin scad catches. The remaining 77% is influenced by other factors. The correlation

test results show that the value of “r” (correlation coefficient) is 0.47. It shows that the

relationship between chlorophyll-a concentration and shortfin scad catches in Pekalongan

waters, Central Java is categorized as a weak relationship due to the value of r <0.7 (Walpole

1995).

Besides this, the relationship of chlorophyll-a with shortfin scad catches is said to be not

tight because chlorophyll-a is not the only indicator that can indicate a potential fishing area. In

addition to chlorophyll-a, indicators that are usually used to determine potential fishing areas

are SST and current. The graph of the relationship between chlorophyll-a to shortfin scad

catches is shown in Figure 6.

Figure 6. The correlation coefficient between catch result and chlorophyll-a time lag

The concentration in an ocean is closely related to the food chain when the chlorophyll-a

concentration is high, and it will increase zooplankton productivity. Moreover, it can create a

food chain that supports fish productivity in water. The trend of increasing or decreasing the

concentration of chlorophyll-a and the catch of shortfin scad can be said to be almost the same,

but the peak increase in the concentration of chlorophyll-a and shortfin scad catches did not

occur at the same time. The time difference shows that the concentration of chlorophyll-a does

not directly affect the fish catches in Pekaongan waters of Central Java but requires time lag for

chlorophyll-a to be utilized by pelagic fish (Chandra and Musuka 2012). According to Simbolon

and Girsang (2009), the time lag between an increase in chlorophyll-a and an increase in the

number of fish catch is 30 days.

y = 580263x - 176474R² = 0,23

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3. 4. Determination of Potential Fishing Areas

The fishing ground is one of the crucial factors in determining the success of the fishing

activity. Seawater can be said to be a fishing area if there are interactions between the fish that

are the target of catching and the fishing technology used to catch fish. Based on the results of

interviews with fishers who landed shortfin scad in Pekalongan PPN, the catching area of

shortfin scad is scattered around the seawaters of North Pekalongan. The ship used is a type of

mini purse seine. The ship has a volume that varies from 10-30 GT.

Potential fishing area categories of shortfin scad are made based on the fishing season,

namely the west season (September-February) and east season (March-August) which are based

on two indicators including the amount of fish catch and chlorophyll-a concentration in shortfin

scad fishing areas in the seawaters of North Pekalongan. Furthermore, the spatial and temporal

categories of potential shortfin scad areas are assessed. In accordance with the assessment of

the DPI indicator, it can be seen that the shortfin scad area has 25 potential coordinates which

are divided into 13 potential coordinates in the east and 12 potential coordinates in the west

season. The DPI distribution map is made based on the scoring that has been done by taking

into account the optimum number of fish catches and chlorophyll-a for shortfin scad activities.

Judging from the chlorophyll-a concentrations scattered in Pekalongan waters, it can be

indicated that potential fishing areas are found in Figure 7.

Figure 7. Fishing Potential Areas distribution in Pekalongan seawaters

The results of the distribution of potential shortfin scad fishing areas indicate that

oceanographic parameters influence fishing activities, although using one of the parameters


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does not show high significance. According to Daqamseh (2013), the accuracies of mapping

fishing potential areas were low due to considering on single correlation with only one

oceanographic parameter. One alternative is to overlay two variables including combining the

contours between SST (Sea Surface Temperature) and the chlorophyll-a contour in order to

obtain a more optimal calculation result.

One of the most significant factors in determining DPI is oceanographic parameters,

which causes fish to choose a place according to their physiological conditions, thus affecting

patterns of fish behavior, in the form of moving motion for adjusting to conditions favorable to

their existence. As for determining potential fishing grounds, another method should be

implemented, such as in situ sampling survey. (Patra et al. 2018)

4. CONCLUSIONS

Based on the results of research by determining the potential fishing area of shortfin scad

and chlorophyll-a distribution in Pekalongan, it can be concluded that there are 25 coordinates

of potential shortfin scad where 13 potential coordinates in the east and 12 potential coordinates

in the west monsoon. Based on statistical analysis, it can be overviewed that the concentration

of chlorophyll-a affects 23% of the shortfin scad catches in the waters of Pekalongan, and the

rest is influenced by other factors.

Acknowledgment

The authors would like to thank the NASA for the chlorophyll-a data and PPN Pekalongan for production of

shortfin scad data.

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