LIMNOLOGICAL CHARACTERISTICS AND LIMNOLOGICAL CHARACTERISTICS AND CAGE CULTURE PRACTICE IN CAGE CULTURE PRACTICE IN

INDRASAROBAR RESERVOIR OF NEPALINDRASAROBAR RESERVOIR OF NEPAL

Madhav K. Shrestha (IAAS, Chitwan, Nepal)Narayan P. Pandit (FDC, Hetauda, Nepal)

World Aquaculture Conference 2008, 19-23 May, Busan, South Korea

AquaFish CRSPAquaFish CRSPUSAIDUSAID

The Aquaculture CRSP is funded in part by United States Agency for International

Development (USAID) Grant No. EPP-A-00-06-00012-00.The opinions expressed herein are those of the authors and do not

necessarily reflect the views of the US Agency for International Development.

ACKNOWLEDGEMENTS

This research was funded by National Agricultural Research and Development Fund (NARDF), Nepal.

All the funding for attending WAS ’08 was made by AquaFish CRSP.

IntroductionIntroduction

• Indrasarobar reservoir Indrasarobar reservoir was built by damming was built by damming in small river valley of in small river valley of mountain region of mountain region of central Nepal.central Nepal.

• Established in 1982 for Established in 1982 for hydropower generation.hydropower generation.

• Lies at the altitude of Lies at the altitude of 1430 m from mean sea 1430 m from mean sea level (msl) at bottom.level (msl) at bottom.

• When filled it reaches When filled it reaches 1530 m msl.1530 m msl.

• Reservoir is 7 km in Reservoir is 7 km in length and 50-500 m in length and 50-500 m in width.width.

• Total area is 216 ha Total area is 216 ha when filled and 55 ha when filled and 55 ha when dry.when dry.

Introduction….Introduction….

• Water depth lowest 60 Water depth lowest 60 m and highest 100 m .m and highest 100 m .

• Reservoir is fed with Reservoir is fed with seven small streams. seven small streams.

• Filled during rainy Filled during rainy season and draw down season and draw down continuously till next continuously till next rainy season occurs.rainy season occurs.

Introduction….Introduction….

• Started in 1988Started in 1988

• Technology copied Technology copied from Phewa lake from Phewa lake (Extensive system)(Extensive system)

• Fish Species:Fish Species:• Silver carp Silver carp • Bighead carpBighead carp

Cage cultureCage culture

Cage culture ……Cage culture ……

• Cage size:Cage size:• 5 m x 5 m x 2 m5 m x 5 m x 2 m• 50 m50 m3 3 ( in general)( in general)

• Stocking density: Stocking density: • 10 fish/m10 fish/m33

• Feeding: Feeding: • NoneNone

Cage Cage MaterialsMaterials

• Bamboo poles for frame Bamboo poles for frame as well as for floatas well as for float

• Recently plastic drum as Recently plastic drum as floatsfloats

• Nylon net Cage:Nylon net Cage:• Nursery cage – 10 mm Nursery cage – 10 mm

meshmesh• Grow out cage - 20 – Grow out cage - 20 –

50 mm mesh50 mm mesh

Cage culture expansion and production Cage culture expansion and production

trendtrend YearYear House-House-

hold (no)hold (no)Cage Cage

(no)(no)Cage Cage

Volume Volume (m(m33))

Total prodTotal prodnn

(mt)(mt)

198198

88

199199

33

199199

88

200200

33

200200

44

200200

55

200200

66

200200

77

55

4747

8686

178178

189189

193193

205205

230230

55

7878

346346

576576

719719

11551155

11951195

16001600

125125

19741974

1287512875

2027920279

3317333173

5418754187

5619756197

7500075000

--

--

4747

7171

116116

103103

107107

134134

Increased cage landing

Cage culture expansion trendCage culture expansion trend

0

10000

20000

30000

40000

50000

60000

70000

80000

Year

Cag

e vo

lum

e (m

3)

Cage productivity and Open water catch of Cage productivity and Open water catch of reservoirreservoir

YearYear Productivity in Productivity in cage (kg/mcage (kg/m33))

Open water Open water

Catch (mt)Catch (mt)

19961996

19971997

19991999

20012001

20032003

20052005

20072007

3.703.70

3.653.65

3.923.92

3.573.57

3.503.50

1.901.90

1.841.84

--

4.04.0

4.54.5

5.25.2

3.03.0

2.02.0

2.02.0

Total cage fish production trendTotal cage fish production trend

020406080

100120140160

Year

Tota

l Pro

duct

ion

(mt)

Productivity trend of cage fish culture in Productivity trend of cage fish culture in reservoirreservoir

0.0

0.5

1.01.5

2.0

2.5

3.03.5

4.0

4.5

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

Year

Pro

du

ctiv

ity (

kg/m

3 /yr)

Trend of fish catch from reservoirTrend of fish catch from reservoir

0

1

2

3

4

5

6

Year

Fish

cat

ch (m

t)

Limnological Characteristics of Limnological Characteristics of ReservoirReservoir

ParameterParameter MeaMea

nn

MaxMax MinMin

Depth (m)Depth (m)

Temperature (Temperature (00C)C)

Dissolved oxygen Dissolved oxygen

(mg/L)(mg/L)

pHpH

Conductivity Conductivity

((μμmhos/cm)mhos/cm)

Transparency (m)Transparency (m)

8080

19.619.6

8.48.4

8.48.4

9696

4.44.4

96 (Oct - 96 (Oct -

Dec)Dec)

24.9 (Jul)24.9 (Jul)

11.7 (Jun)11.7 (Jun)

9.5 (Mar)9.5 (Mar)

126 (May)126 (May)

6 (Feb)6 (Feb)

62 (May)62 (May)

12.2 (Feb)12.2 (Feb)

5.9 (Dec)5.9 (Dec)

7.6 7.6

(Dec/Jan) (Dec/Jan)

59 (Feb)59 (Feb)

3 (Nov)3 (Nov)

Monthly mean and range of water quality parameters of reservoir during May 2006 to April 2007

Monthly mean water depth of the Monthly mean water depth of the reservoirreservoir

50

60

70

80

90

100

20-M

ay

19-J

un

19-J

ul

18-A

ug

17-S

ep

17-O

ct

16-N

ov

16-D

ec

15-J

an

14-F

eb

16-M

ar

15-A

pr

Date

Wat

er d

epth

(m

)

Monthly water temperature during 2006-Monthly water temperature during 2006-20072007

10

12

14

16

18

20

22

24

26

20-M

ay

19-J

un

19-J

ul

18-A

ug

17-S

ep

17-O

ct

16-N

ov

16-D

ec

15-J

an

14-F

eb

16-M

ar

15-A

pr

Date

Tem

pera

ture

(0 C

)

Limnological Characteristics…….Limnological Characteristics…….

ParameterParameter MeaMeann

MaxMax MinMin

Total alkalinity (mg/L)Total alkalinity (mg/L)

Total suspended solids Total suspended solids

(mg/L)(mg/L)

Total dissolved solids Total dissolved solids

(mg/L)(mg/L)

BODBOD55 (mg/L) (mg/L)

Chlorophyll-a (mg/mChlorophyll-a (mg/m33))

5757

146146

266266

4.84.8

8.58.5

65 65

(Mar)(Mar)

980 980

(Aug)(Aug)

382 382

(Aug)(Aug)

5.6 5.6

(Dec)(Dec)

20.7 20.7

(Sep)(Sep)

50 50

(Sep)(Sep)

48 48

(Sep)(Sep)

45 45

(Sep)(Sep)

3.7 3.7

(Aug)(Aug)

2.7 2.7

(May)(May)

Monthly mean chlorophyll-a during Monthly mean chlorophyll-a during 2006-20072006-2007

0.0

5.0

10.0

15.0

20.0

25.0

20-M

ay

19-J

un

19-J

ul

18-A

ug

17-S

ep

17-O

ct

16-N

ov

16-D

ec

15-J

an

14-F

eb

16-M

ar

15-A

pr

Date

Chl

orop

hyll-

a (m

g/m

3 )

Limnological Characteristics…….Limnological Characteristics…….

ParameterParameter MeaMeann

MaxMax MinMin

Total Nitrogen (mg/L)Total Nitrogen (mg/L)

Total ammonium-N Total ammonium-N

(mg/L)(mg/L)

NONO22-N (mg/L)-N (mg/L)

NONO22+NO+NO33-N (mg/L)-N (mg/L)

Total Phosphorus Total Phosphorus

(mg/L)(mg/L)

SRP (mg/L)SRP (mg/L)

1.031.03

0.080.08

0.020.02

55

0.060.06

55

0.150.15

0.030.03

1.33 1.33

(Aug)(Aug)

0.15 0.15

(Aug)(Aug)

0.051 0.051

(Sep)(Sep)

0.106 0.106

(Jan)(Jan)

0.22 0.22

(Dec)(Dec)

0.06 0.06

(Dec)(Dec)

0.56 0.56

(May)(May)

0.04 (Feb)0.04 (Feb)

0.008 (Jun)0.008 (Jun)

0.014 0.014

(May) (May)

0.06 0.06

(May)(May)

0.02 (Feb)0.02 (Feb)

Monthly mean total nitrogen (TN) and total Monthly mean total nitrogen (TN) and total phosphorus (TP) trend in reservoir during 2006-phosphorus (TP) trend in reservoir during 2006-20072007

0.0

0.5

1.0

1.5

2.0

2.5

20-M

ay

19-J

un

19-J

ul

18-A

ug

17-S

ep

17-O

ct

16-N

ov

16-D

ec

15-J

an

14-F

eb

16-M

ar

15-A

pr

Date

Nut

rient

con

tent

(m

g/L)

TN TP

Monthly mean total ammonium nitrogen (TAN) and Monthly mean total ammonium nitrogen (TAN) and soluble reactive phosphorus (SRP) content trend in soluble reactive phosphorus (SRP) content trend in reservoir during 2006-2007.reservoir during 2006-2007.

0.00

0.02

0.04

0.06

0.08

0.100.12

0.14

0.16

0.18

0.20

20-M

ay

19-J

un

19-J

ul

18-A

ug

17-S

ep

17-O

ct

16-N

ov

16-D

ec

15-J

an

14-F

eb

16-M

ar

15-A

pr

Date

Nut

rient

con

tent

(m

g/L)

TAN SRP

ConclusionConclusion

• Increased cage landing has decreased Increased cage landing has decreased productivity – Plankton limitationproductivity – Plankton limitation

• Mean fish harvest size has been Mean fish harvest size has been decreaseddecreased

• Current cage culture is about 4 ha Current cage culture is about 4 ha which is about 2% area of the reservoir which is about 2% area of the reservoir when fully filled and about 7% of the when fully filled and about 7% of the reservoir when lowest water level.reservoir when lowest water level.

RecommendationRecommendation

OptionsOptions

• Decrease cage culture areaDecrease cage culture area

• Decrease stocking densityDecrease stocking density

• Introduce feeding system which will support non Introduce feeding system which will support non feeding cage culture system too.feeding cage culture system too.

Currently Government has chosen recommendation Currently Government has chosen recommendation # 2 and has asked cage culture farmer to reduce # 2 and has asked cage culture farmer to reduce stocking density by 50% (10 to 5/mstocking density by 50% (10 to 5/m33))