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STATUS OF RESERVOIR FISHERIES IN BATANG AI HYDROELECTRIC DAM, SRI AMAN, SARAWAK

Nazhatul Nazereen Binti RosH (31547)

QL Bachelor of Science with Honours120

(Aquatic Resource Science and Management)N33S 20142014

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Pusat Khidmat MakJUlDat Abdernik UNtVERSRl MALAYSIA SARAWAK, ;'.

Status of Reservoir Fisheries in

Batang Ai Hydroelectric Dam, Sri Aman, Sarawak

Nazhatul Nazereen Binti Rosli (31547)

)

This project is submitted in partial fulfillment of

the requirement for the Degree of Bachelor of Science with Honours

(Aquatic Science and Resource Management)

Faculty of Resource Science and Technology

, - Universiti Malaysia Sarawak

2014

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ACKNOWLDEGEMENT

During the course of this project, many people have made invaluable contributions

towards the completion of this final year project. Most importantly, a sincere appreciation

to my supervisor, Prof. Dr. Lee Nyanti for his invaluable guidance, help, advice and

support throughout this journey.

I am also thankful for the help provided by the laboratory assistants from

Department of Aquatic Science, FRST especially Mr. Zaidi Ibrahim, Mr Richard Toh, Mr

Nasri Latib, Mr Mohd Nor Azlan andMr Harris during field works and at the laboratory.

t I would also like to forward million thanks to all the fishermen at Batang Ai

Reservoir, Sri Aman, Sarawak for making their valuable time for interview session and

special appreciation to SALCRA especially Mr. Raymond, Ms. Umi, Mr. Munan, Mr.

Musa, Mr. James, and the local assistants namely Mr. Helmi, and Mr. Sempurai for their

assistance.

A big thank you to all my beloved family members especially Ibu, Ayah, Abang

Akeem, Moy, Ameen,· Aim and Nurin for all the supports, and thank you for always

cheered me up through thick and thin. Without fail, thank you to all my close friends

including Hanisah, Syazwani, Masania, Farahaisha, Naemah, Ezzaty, Fatin, Ayu Fitrie and

Roziana, my field work mates Finaz and Nadhirah, and to all final year students ofAquatic

Science Department, FRST for helps and supports.

The financial support provided by Sarawak Energy Berhad through research grant

no. GL(F07)/SEB/~Al2013 (28) is gr~tefully acknowledged.

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DECLARATION

I, Nazhatul Nazereen Binti Rosli, declare that the final year project entitled

"Status of Reservoir Fisheries at Batang Ai Hydroelectric Dam, Sri Arnan, Sarawak"

submitted in partial fulfillment of the requirement for the Degree of Bachelor of Science

with Honours (Aquatic Resource Science and Management) is the bonafide record of the

original research work carried out by me, that I have exercised reasonable care to ensure

that the work is original, and has not been taken from the work of others and to the extent

that such work has been cited and acknowledged within the text ofmy work.

(Nazha

Aquatic Resource Science and Management

Faculty ofResource Science and Technology

Universiti Malaysia Sarawak

Date: '10 Jwlf 1ft ~4--

ii

-Pusat Khidmat Maklumat Akademh~ UNIVERSfll MALAYSIA SARAWAK

j .,

TABLE OF CONTENTS

TITLE PAGES

Acknowledgement

Declaration 11

Table of Contents III

List of Abbreviations v

List of Tables VI

List of Figures VII

Abstract viii

1.0 INTRODUCTION 1

2.0 LITERATURE REVIEW 3

2.1 The Concept of Reservoir 3

2.1.1 Reservoir and Fisheries 3

2.1.2 Batang Ai Reservoir 4

2.2 Factors Influencing Fish Assemblages in Reservoir 4

2.3 Factors Influencing Species Composition in Reservoir 6

3.0 METHODOLOGY 7

3.1 Study Site 7

3.2 Sample Collection 9

3.2.1 Water Quality 9

3.2.2 Fish 11

3.3 Fish Species Identification 11

3.4 Fish Measurement 11

3.4.1 Length-Weight Relationship 12

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123.4.2 Gonadal Somatic Index (GSI)

123.5 Fish Preservation

133.6 Fish Analysis

133.6.1 Indices

143.6.2 Fisheries Production

143.7 Water Quality Analysis

154.0 RESULTS

154.1 Water Quality Parameter

224.2 Fish Fauna

224.2.1 Species Composition

4.2.2 Diversity, Richness and Evenness Indices 25

4.2.3 Length-Weight Relationship (L WR) 26

4.2.4 Gonadal Somatic Index (GSI) 28

294.2.5 Fisheries Production

365.0 DISCUSSION ·

436.0 CONCLUSION

447.0 REFERENCES

49APPENDIX

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LIST OF ABBREVIATIONS

rpm Revolutions per minute

L Litre

mL Millilitre

Ilg Microgram

E Absorption in the respective wavelength

LWR Length-Weight relationship

GSI Gonado-Somatic Index

TSS Total Suspended Solids

DO Dissolved Oxygen

I FNU Formazin Nephelometric Units

mglL Milligram per Litre I

DC Degree Celcius

kg ha-' yr-' Kilogram per hectares per year

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LIST OF TABLES

Table Title Pages

Table 1 Coordinates of the sampling stations. 8

Table 2 The mean value and standard deviation of the water quality 16 parameters taken at all stations.

Table 3 Comparison of chlorophyll-a values among stations at three different 21

depths.

Table 4 Comparison of chlorophyll-a values within station at three different 21

depths.

Table 5 Species composition of fish from all stations. 24

Table 6 Diversity, richness and evenness indices recorded at all stations. 25

Table 7 Length-weight relationship and condition factor (k) for three different 26 species.

Table 8 Educational level, marital status (no. ofhousehold), and years of 29 experience as full time fishermen at the reservoir.

Table 9 Types ofboat, outbound engine used and additional economic 30 activities carried out by the full time fishennan at the reservoir.

Table 10 Methods of fishing used by the fuH time fishennen at the reservoir. 30

Table 11 Proportions of catch (kg) of target species and favorite fishing spot of 31 the full time fishermen at the reservoir.

Table 12 Monthly catch condition of the full time fishermen at the reservoir. 32

Table 13 Pattern of fishing and number of fishing trips per month and year 33 (times) of the full time fishennen at the reservoir.

Table 14 Total cost of fishing per year, values offish caught per year and gross 34 earning per year for the full time fishermen at the reservoir.

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LIST OF FIGURES

Figures Title Pages

Figure 1 Location of the sampling stations at Batang Ai Reservoir, Sarawak 7

(Source: Ooogle Map and Ooogle Earth).

Figure 2a Temperature profile with depth from station 1 to 6. 17

Figure 2b Temperature profile with depth from station 7 to 12. 18

Figure 3 Water quality parameters recorded at each station. 19

Figure 4 Chlorophyll-a values at three depths recorded from four stations. 21

Figure 5 Percentage of family caught at all stations. 22

• IFigure 6 Comparison ofmean of slope b (growth pattern) among three fish -26

species. J. Figure 7 Length-weight relationship for three fish species. 27

Figure 8 OSI of three different fish species. 28

Figure 9 Total fish landings (kg) per year for individual fisherman. 34

Figure 10 Value of catch (RM) per year for individual fisherman. 35

Figure 11 Fishing cost (RM) per year for individual fisherman. 35

Figure 12 Gross earning (RM) per year for individual fisherman. 35

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Status of Reservoir Fisheries in Batang Ai Hydroelectric Dam, Sri Arnan, Sarawak

Nazhatul Nazereen Binti Rosli

Department of Aquatic Science Faculty of Resource Science and Technology

University Malaysia Sarawak Malaysia

Abstract

A study was carried out to document the status of reservoir fisheries including water quality and fish fauna at Batang Ai Reservoir due to the lack of published information. Twelve sampling stations were selected for fish and water sample collection. Results shows that depths in the study stations ranged from 20 to 110 m and pH values ranged from 5.73 to 7.92. Water temperature ranged from 26.3 to 31.13 oC, and was in decreasing trend as depth increased. DO concentrations at all stations were above 7 mgIL. Chlorophyll-a value was the highest at 20 m depth at station 10 and lowest at sub-surface of station 9. A total of 8 families represented by 17 species of fish were caught from the reservoir. The most dominant family in tenns of the number of individuals caught is Cyprinidae. Barbonymus schwanenfeldii is the most dominant species with the highest number of individuals caught. Length-weight relationship of the three species in the reservoir shows b value ranging from 2.79 to 2.88 which indicate that the fish has negative allometric growth Gonadal Somatic Index (GSI) ranged from 1.09 to 3.24. The average fisheries production in the reservoir range from 17.12 to 20.55 kg ha-1

yr-l. Therefore, proper management of the reservoir should be done to sustain the fisheries production in Batang Ai Hydroelectric Dam, Sarawak.

Keywords: Reservoir fisheries, fisheries production, fish fauna, LWR, GSI.

Abstrak

Satu kajian telah dijalankan bertujuan mendokumenkan status perikanan yang merangkumi kualiti air dan fauna ikan di ~mpangan Batang Ai kerana kurangnya maklumat yang telah diterbitkan. Dua belas stesen pensampelan telah dipilih untuk koleksi ikan dan sampel air. Keputusan menunjukkan bahawa kedalaman air di stesen-stesen kajian adalah di antara 20 hingga 110 m dan pH adalah di antara 5.73 hingga 7.92. Suhu air adalah di antara 26.3 hingga 31.13 °C, dan suhu menurun dengan pertambahan kedalaman. Kelarutan oksigen di semua stesen adalah lebih dari 7 mg/L. Nitai k1orofil-a di kedalaman 20 m pada stesen 10 adalah yang paling tinggi dan paling rendah adalah di permukaan stesen 9. Lapan famili diwakili 17 spesis ikan telah ditangkap dari empangan. Berdasarkan jumlah individu ikan yang paling banyak ditangkap, famili yang paling dominan ialah Cyprinidae. Barbonymus schwanenfoldii adalah spesies yang paling dominan. Hubungan panjang-berat untuk tiga spesies di empangan menunjukkan nitai b di antara 2. 79 hingga 2.88. Ini menunjukkan bahawa ikan mempunyai kadar pertumbuhan alometrik yang negative. Nitai 'Gonadal Somatic Index (GSI) , adalah di antara 1.09hingga 3.24. Purata produksi perikanan setiap tahun di empangan ialah di antara 17.12 hingga 20.55 kg ha-J thn-J

• Justeru, pcngurusan di empangan haruslah dilakukan supaya pengeluaran perikanan dapat dikekalkan di Empangan Hidroelektrik Batang Ai, Sri Aman, Sarawak.

Kala Kunci: Perikanan empangan, pengeluaran perikanan, fauna ikan, L WR, GSI.

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1.0 INTRODUCTION

Many reservoirs in an over the world are facing eutrophication, sedimentation, weed

infestation and many other problems (Sharip & Zakaria, 2008). Despite the threats faced,

reservoir is very important due to its functions as site for aquaculture and hydropower, as well

as its roles as flood mitigation, silt retention and municipal storage basin (Sharip & Zakaria,

2008), while Nyanti et al. (2012) stated that employment opportunity for the local

communities has been a great influence on the existence of Batang Ai Reservoir due to

tourism and aquaculture activities.

In accordance with the multipurpose functions and the increasing development of the

reservoir, Van Zwieten et al. (20 11) stated that in 2006, 10.1 million tonnes of freshwater

were produced worldwide, of which reservoir fisheries also contributed to the production. In

Malaysia, there are 51 reservoirs. Ambak & lalal (2006) reported that in Kenyir Lake, which

has area of 36 900 ha and depth of 150 m, there are 36 species present in the aquatic

environment and the fisheries production is 1.3 to 20.0 kg ha-1 yr-] while Pergau Reservoir,

Kelantan which has depth of 14 m and area of 2 500 ha, production was estimated at 22.0 kg

ha-1 yr-] of fishes from 20 species. Pergau Reservoir has higher fisheries production than

Kenyir Reservoir as shallow reservoir is said to be more productive than deeper reservoir

(Ambak & lalal, 2006).

Therefore, in particular with the various functions that the reservoir holds, ecological

and social-economic aspect is very important in order to manage and develop the

sustainability of reservoir by evaluating the fisheries status (Ara et aI., 2010). According to

Kamaruddin et al. (20 11), study on fish species diversity, abundance and distribution in the

reservoir is very important in order to reduce the effect of the threats to the fish community.

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Abdullah (2004) proposed the monitoring system be done where data collected should

include the number of fishermen and fish production in Batang Ai Reservoir. Such study

should be initiated to ensure sustainable resource use and to develop the strategic development

plan for the local communities.

Therefore, due to the absence of published information on the status of fisheries in

Batang Ai Reservoir, Lubok Antu this study was conducted so that the current fisheries status

in the Batang Ai Reservoir could be documented.

Therefore, the objectives of this study were:

i. To determine the water quality at selected stations in the reservoir,

11. To record the species composition of fish present in the Batang Ai Reservoir,

lll. To document the current status of fisheries at Batang Ai Reservoir, and

IV. To estimate the fisheries production in Batang Ai Reservoir.

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2.0 LITERATURE REVIEW

2.1 The Concept of Reservoir

2.1.1 Reservoir and Fisheries

Reservoir is a complex and variable storage which act as a link between the river and

the natural lake to support the water system in the environment (Okada et aI., 2005). Sugunan

(1995) described reservoir as any water course, river or streams that is being obstructed by the

surface flow of the dam or any description resulting in a man-made impoundments of more

than 10 ha.

For the purpose of fisheries management, the size and depth of the reservoir is an

important factor in determining the production of fisheries as Ambak & lalal (2006) stated that

differences in depth of the reservoir gives different value of fisheries production. De Silva &

Funge-Smith (2005) define the size of reservoir as large impoundments when it is dammed by

large rivers and small reservoirs are defined when the impoundment is dependent on the

rainfall and the runoff from the local catchments. Van Zwieten et al. (2011) divide the size of

the reservoir into three types, where the size of small reservoir is less than 1000 ha in area,

medium at 1000-5000 ha in area and large at more than 5000 ha in area.

The production of fisheries by the local fishermen in the reservoir area is dependent on

many factors such as costs and types of fishing gear used. However, most of the inland

fisheries such as in reservoir are smaller scale which is done individually or in a small group

by using seines, nets, traps, hooks and lines (Abu Talib et al., 2003).

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2.1.2 Batang Ai Reservoir

Batang Ai Hydroelectric Reservoir which was impounded in 1985 is located 260 km

from Kuching at coordinates 01°08'50" N; 111°52'26" E. The reservoir receives inflow water

from two main rivers which are Batang Ai and Engkari River. This reservoir has a surface area

of 84 ha at full supply and catchment area of 1200 km2 with elevation of 108 m.

Abdullah (2004) reported a total of 63 species of fish present in Batang Ai National

Park, specifically between the headwater region and the inundated waters of the dam. The fish

population faced several threats such as overfishing, released of introduced species into the

waters and loss of habitat due to the increased level of the inundated waters of the lake. lalal et

al. (2012) also stated that factor such as overexploitation of species, pollution, and changes in

the environment due to damming and water diversion has led to the decline of fisheries and

fish communities in the aquatic environment.

Therefore, the reservoir must be maintained at optimum condition to ensure the

continual presence of fisheries resources in the reservoir. This is important so that the future

generation can also uSe the fisheries resources as their sources of income and food

(Phounsavath, 1998).

2.2 Factors Influencing Fish Assemblages in Reservoir

The technical aspects in reservoir fisheries include irrigation and flooding of the

reservoir that influenced the fish assemblages in the reservoir. This is because the volume of

water has direct influence on water quality of the reservoir, thus affecting the growth and

population of fish in the area (Phounsavath, 1998). Ambak & lalal (2006) stated that the

4

Pusat Khidmat Maklumat Akadem· \ UNlVERSm MALAYSIA SAKAWAK

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nature of fish species, habitat association, morphological and limnology characteristics of the

reservoir also influenced the distribution of fish in the reservoir.

According to Sreekantha & Ramachandra (2005), the beginning of monsoon is the best

season to yield high production of fish in Linganamakki Reservoir, India while low values of

dissolved oxygen during dry seasons can give hannful effect. Imam et al. (2010) stated that

fish in stagnant water especially in polluted water have the tendency to be negatively

influenced in tenns of their feeding capacity. This shows that different seasons of the year and

water quality influenced the fish assemblages in the reservoir.

It is also suggested that the frequencies of fish assemblages present at certain area is in

accordance with the availability of the vegetation in that particular area (Sreekantha &

Ramachandra, 2005). Pelicice et al. (2005) reported that 96 % of all the fish assemblages in

Parana Reservoir, Brazil were caught in the area with medium and high macrophyte density.

This shows that there is a relationship between fish and macrophyte density in the reservoir.

Ambak & lalal (2006) also revealed that the fonner riverine species of fish that is present in

the Kenyir Reservoir, Malaysia, is dependent on the forests product such as seeds and fruits,

provided that some of the fish can easily adapt to the environment.

Agostinho et al. (1999) stated that after the original filling period of the Upper Parana

River Basin, Brazil, the fish in certain parts of the reservoir has become herbivorous as the

diets of the fish in the reservoir has become more stable to feed on the macrophyte rather than

feeding on the detritus. This is influenced by the environmental factor that changes the

condition of the reservoir, most notably the nutrient accumulation and siltation.

5

2.3 Factors Influencing Species Composition of Reservoir Fisheries

Species distribution in a particular area is dependent on the factors of location-wise

and seasons-wise as mentioned by Sreekantha & Ramachandra (2005). This is proven as they

found that in monsoon season, there are major fish catch of introduced species, while as the

season ends, the value drops and the indigenous species dominated in the Linganamakki

Reservoir, India.

Zakaria et al. (2000) reported that during the wet season with a peak of the spawning

period, the fish contained matured eggs and spenns indicating that there is an increase in value

of number of fish per species in Kenyir Lake. Kamaruddin et al. (2012) reported that the

condition of all species in Kenyir Lake is high during February/April season indicating that

there are food organism present during the season as well as there are difference in gonadal

development of the fish. This shows that the availability of food during certain seasons has

influence on the species present in the area.

Besides, breeding of fish also influenced the species composition of the reservoir

fisheries as some of the fish can breed within the reservoir, or migrate to smaller distances in

search of shallower areas. This makes the species present in a particular area to vary.

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3.0 METHODOLOGY

3.1 Study Site

This study was carried out at Batang Ai Reservoir, Sri Aman, Sarawak. Twelve

stations were selected as sampling sites as shown in Figure 1.

Figure 1: Location of the sampling stations at Batang Ai Reservoir, Sarawak (Source: Google Map and Google Earth).

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Two of the stations (Stations 1 and 2) were located at the edge of the reservoir, two

stations (Stations 3 and 4) at the middle of the reservoir, two stations (Stations 5 and 8) were

located near the cage culture sites, two stations (Stations 6 and 7) were located near the

tributaries of Bungin and Ramin river, two stations (Stations 9 and 10) were located at the

Genting Penyaru area, Station 11 was near to the Hilton area while Station 12 was located

between the dam and the jetty area. The coordinates of all the stations recorded using Global

Positioning System (GPS) is shown in Table 1.

Table I: Coordinates of the sampling stations.

Station Coordinates Locations

N 01 ° 08' 51.4" £ III °53'13.6"

2 NOl o 07' 48.3" £ 111°53'37.6"

3 NOlo 09' 06.7" £ 111°54'54.9"

4 NOl o 09' 01.4" £ 111°53'03.8"

5 NOl o 10' 34.1" £ 111°51'56.1"

6 N 01 ° 11' 16.1" £ 111°52'09.5"

7 N 01 ° 11' 38.9" £ 111°51 '09.6"

8 NOlO 11' 14.6"£ 111°51'26.4"

9 NOl o 08' 25.4" £ 111°53'37.7"

10 NOlo 08' 06.11" £111°55'22.0"

11 NOlO 11' 19.0"£ 111°55'46.3"

12 N 01 ° 08' 07.4" £ 111°51 '37.6"

At the edge of the reservoir

At the edge of the reservoir

At the middle of the reservoir

At the middle of the reservoir

Near Able cage culture

Sungai Bungin

Sungai Ramin

Near Wong cage culture

Genting Penyaru

Genting Penyaru

Hilton area

Between the dam and jetty area

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3.2 Sample Collection

3.2.1 Water Quality

In-situ physico-chemical water quality parameters such as depth, pH, temperature,

dissolved oxygen (DO), transparency, turbidity and conductivity and ex-situ physico-chemical

parameters such as Total Suspended Solids (TSS) and chlorophyll-a were recorded. All the

parameters were recorded in triplicates during each water samples collection.

The range of depth at each station was recorded by using depth finder Speedtech

Intruments 67505. The pH of the water was recorded by using pH meter Eutech Instruments,

DO and temperature by using DO meter Sper Scientific 850041, and water transparency was

recorded by using Secchi disc KAHLSICO No. 281 WA 1088, WAP-4669 at each station.

Turbidity of water was recorded by using turbidity meter Martini Instruments MI415.

Water samples were collected by using Van Dorn Water Sampler and transferred into 2

L of plastic bottles that were collected in triplicates. Water samples for chlorophyll-a analysis

were collected at stations 9, 10, 11 and 12 in triplicates from three different depths, which are

at the subsurface, at 1 Qm depth and at 20 m depth of the reservoir. Then, all the bottles were

placed in a cooler box and brought to the laboratory for analysis.

For TSS analysis, filter paper was dried overnight in oven under the temperature 103­

105°C and then the filter paper was weighted. Using dried filter paper, water samples of

known volume was filtered. Next, the filter paper was dried overnight and was weighted until

constant values were achieved. TSS values were obtained by deducting the final weight with

initial weight and finally divided the value by volume of water used in filtration (APHA,

2000).

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For chlorophyll-a analysis, water samples of known volume were filtered by using

vacuum pump where filter paper containing chlorophyll-a was analyzed. The samples were

then grinded for 5 minutes by using grinder with 5 to 6 mL of 90 % acetone was added into

the mortar. The samples were transferred into a capped test tube before 90 % acetone was

added into the test tube to make up the volume to 10mL. The test tube was wrapped with

aluminium foil and was placed in the refrigerator at temperature 4 °C for 4 to 18 hours to

facilitate complete extraction of the pigments. Then the liquid was transferred into centrifuge

tube and was placed into a centrifuge for about 10 minutes under 3000 rpm. Optical density

was determined using spectrophotometer at wavelength of 750 om, 664 om, 647 om, and 630

Dm. Extinction for each of the small turbidity blank was corrected by subtracting 750 om from

664 om, 647 om, and 630 om absorptions (APHA, 2000).

The concentration of chlorophyll-a in the extract after correction:

Chlorophyll-a = 11.85(E664--E750) - 1.54(E647-E750) - 0.08(E630- E750)

Where E =the absorption in the respective wavelength

Calculation of the amount chlorophyll-a per unit volume is as follow:

mg) Cax v Chla (L =-y

Where: Ca = Chlorophyll concentration in /!glmL v = Volume of acetone in mL V= Volume of samples in L

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3.2.2 Fish

In station 1 to 12, fishes were caught by using monofilament gill net of different mesh

sizes which are 5 cm, 10 cm, and 18 cm, as well as three layer gill nets with mesh size of 13.5

cm, 3.5 cm, and 13.5 cm. The nets were left overnight from 1700 hours until 0600 hours. The

next day the nets were checked and all fish caught were collected. Fish samples from Jengin

station were obtained from the commercial fishermen caught using 5 cm, 7 cm, 8 cm, 10 cm,

11 cm, 12 cm, and 20 cm. Survey was also conducted through questionnaires according to

Halliday et at. (2002) in order to collect information on the current status of reservoir fisheries

(see Appendix 1.0).

3.3 Fish Species Identification

Fishes collected from every station were segregated and enumerated according to

species during the field sampling. Identification of the specimen was carried out based on the

taxonomic method according to Tan (2006), Inger & Chin (2002), Kottelat et al. (1993),

Roberts (1989), and Mohsin & Ambak (1983). Additional reference to check on the current

status offish taxonomy was made using the website offish base (Fishbase, 2014).

3.4 Fish Measurement

Standard length, total length and weight of the fish specimens were measured. The

standard length and total length of the specimens were measured using a ruler, while the

weight of the fish specimen was measured by using the analytical balance model AND GF­

300 with 2 decimal points.

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3.4.1 Length-Weight Relationship

The growth and condition of fish were analyzed by using length-weight relationships

(LWRs) method. Length-weight relationship of the fish was estimated using the fonnula, W =

aLb, where Wand L are the weight (in g) and total length (in cm), respectively. The fonnula

was logarithmic transfonned to obtain a linear expression, In W = In a + b In L, where a and b

are the intercept and slope of the straight line, respectively. The b value indicated the type of

growth of fish, b=3.0 (isometric or nonnal growth rate), b>3.0 (positive allometric or over

growth rate) and b<3.0 (negative allometric or poor growth rate). Fulton's condition factor (K)

was detennined with the fonnula, K = lOOWIL3• The metric indicated that the higher the K

value the better the condition of fish.

3.4.2 Gonadal Somatic Index (GSI)

Gonads were dissected out using dissecting set GOLD CROSS and if the gonads were

present, their weight was measured by using analytical balance AND GF-300 with 2 decimal

points. GS! was calculated using the following fonnulae:

weight of gonads (g) GS! (%)= ... x 100 %

body weIght (mcludmg gonads)

3.5 Fish Preservation

Fishes collected from every station were segregated according to species. The

specimen of each species was preserved in 10 % fonnalin and stored in a plastic container

with proper labeling.

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3.6 Fish Analysis

3.6.1 Indices

Data on the identification of the fish specimens were pooled together to determine the

indices. Three indices that were used are Shannon-Weaver's (H's), Margalefs Species

Richness Index (D) and Pielou's Evenness Index (J's) by using formulae (1) to (3) to calculate

their values.

(1) Shannon-Weaver Diversity Index (H's) (Shannon & Weaver, 1963)

, nlogn- LfilogfiH=--- --­

n

Where: n = Sample size fi = Number of individual for each species

(2) Margalef Richness Index (D) (Margalef, 1968)

(S-l)0=--­

IOglO N

Where: S = Total number of species N = Total number of individual

(3) Pielou Evenness Index (Pielou, 1966)

, H' J=­

Ln S

Where: H' = Diversity of Species S = Total number of species

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3.6.2 Fisheries Production

Interviews were carried out on 11 fulltime fishermen in Batang Ai reservoir.

Questionnaires included data on the information of catches, fishing effort, fishing methods,

fishing seasons and others (Appendix 1.0). Fish caught from the reservoir from each fisherman

were extrapolated to determine the annual fisheries production in unit of kg ha-1 year-1 and was

analyzed in reference to Wijenayake et at. (2005).

3.7 Water Quality Analysis

One-way ANOVA test was used in the statistical analysis by applying a level of

significance at 5 % in order to determine the significance difference on the water quality

parameters within and among stations. Statistical analyses were carried out using SPSS

version 22.0 package.

)

14