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))