POLYCULTURE OF GRASS CARP AND NILE TILAPIA WITH NAPIER GRASS AS THE SOLE

NUTRIENT INPUT IN THE SUBTROPICAL CLIMATE OF NEPAL

Narayan P. Pandit, Madhav K. Shrestha* (IAAS, Nepal)Yang Yi (AIT, Thailand)

James S. Diana (UM, USA)

ACKNOWLEDGEMENT

This Research was funded by Pond/Dynamics Aquaculture CRSP

Project

INTRODUCTIONLow-cost input in naturally balanced pond environment based semi-intensive aquaculture is the preferred systems for the small-scale fish farmers of the developing countries.

Grass carp based polyculture is a traditionally practiced systemwhere grass carp consume low valued grasses and increase natural food production in the pond by nutrient recycling and fecal production.

Several species of filter feeder and detritivorus fish are stocked to utilize the natural food production in pond.

A single species Nile tilapia might be feasible to replace several species carps in grass carp based polyculture to simplify and minimize polyculture and to utilize feeding ‘niche” of pond ecosystem with maintaining natural balance of pond environment.

OBJECTIVES

To evaluate the growth of grass carp and Nile tilapia fed with napier grass in polyculture.

To evaluate water quality regimes of pond water.

To determine the compositions of foods consumed by Nile tilapia.

To determine the optimal ratio of grass carp to Nile tilapia in polyculture.

MATERIALS AND METHODSPond input:Napier grass (Pennisetum purpureum)

A perennial tropical / subtropical fodder grassEasily cultivable in pond dikes, slope areas and in underneath of large treesNeeds minimum management practice

Fish species:1. Grass carp (Ctenopharyngodon idella)

For grass feeding2. Nile tilapia (Oreochromis niloticus)

For natural food utilization of pond ecosystem

MATERIALS AND METHODS (Cont’d)Treatment combinations:

T1: Monoculture of:grass carp @ 0.5/m2

T2: Polyculture of:grass carp @ 0.5/m2

Nile tilapia @ 0.25/m2

T3: Polyculture of: grass carp @ 0.5/m2

Nile tilapia @ 0.5/m2

T4: Polyculture of: grass carp @ 0.5/m2

Nile tilapia @ 1.0/m2

T5: Polyculture of:grass carp @ 0.5/m2

Nile tilapia @ 2.0/m2

MATERIALS AND METHODS (Cont’d)Culture system:

Cemented tank of 24 m2.

Stagnant water system with weekly water added to maintain 1.5 m deep.

Feeding of chopped fresh napier grass leaves at ad libitum everyday as a sole input.

Culture period: 188 days for grass carp and 182 days for Nile tilapia.

Experimental period: May 26 – Nov 30, 2002.

Experimental design: Completely randomized design (CRD)

RESULTS

46.6b

453a

91.72.2a

10.0ab

11.2ab

45.3ab

490a

83.32.4a

9.8ab

11.0ab

44.2a

635b

80.63.1b

12.6b

13.8b

44.2a

471a

80.62.3a

9.0a

10.2a

39.3--0------

Initial wt (g)Final wt (g)Survival (%)Weight gain (g/d)NFY (kg/ha/d)GFY (kg/ha/d)

T5T4T3T2T1Item

Mean stocking and harvest size, survival, growth and net fish yield of grass carp in monoculture and polyculture tanks.

RESULTS (Cont’d)

9.044.0c

1000.19c

3.92d

4.93d

9.356.1b

1000.26b

2.62c

3.15c

10.082.1a

1000.40a

2.02b

2.30b

9.491.4a

1000.46a

1.15a

1.28a

Initial wt (g)Final wt (g)Survival (%)Weight gain (g/d)NFY (kg/ha/d)GFY (kg/ha/d)

T5T4T3T2Item

Mean stocking and harvest size, survival, growth and net fish yield of adult Nile tilapia in polyculture tanks.

Figure 1. Mean weight of grass carp in different treatments during experimental period. All fish died in T1 during 81 days of culture period.

0

100

200

300

400

500

600

700

0 50 100 150 200

Experimental period (days)

Mea

n w

eigh

t (g)

T1T2T3T4T5

Figure 2. Mean weight of Nile tilapia in different treatment during experimental period.

01020304050

60708090

100

0 50 100 150 200

Experimental period (days)

Mea

n w

eigh

t (g)

T2T3T4T5

RESULTS (Cont’d)

13.91

16.18

12.40

14.15

14.62

16.10

10.98

12.31

NFY (kg/ha/d)

GFY (kg/ha/d)

T5T4T3T2Item

Mean Combined NFY and GFY of grass carp and Nile tilapia in polyculture tanks.

RESULTS (Cont’d)

3326.2b

4.76

3537.1b

5.50

5246.5b

8.09

24813.4a

7.68

Nile tilapia RecruitsMean numberMean weight (g)Yield (kg/ha/d)

18.720.9

17.919.6

22.724.2

17.518.8

Total NFY (kg/ha/d)Total GFY (kg/ha/d)

T5T4T3T2Item

Mean Nile tilapia recruits and mean total yield including recruits in polyculture tanks.

RESULTS (Cont’d)

18.6±1.59.2±0.42.0±0.328.6±0.410.0±0.250.2±0.7

Grass

6.3±0.25.2±0.41.4±0.436.0±0.68.2±0.449.2±0.4

Dry matter (DM)Crude protein (CP)Ether extract (EE)Crude fiber (CF)Total ash (TA)Nitrogen free extract (NFE)

FecesConstituents

Proximate composition (%) of fresh napier grass and fresh feces of grass carp in dry weight basis.

RESULTS (Cont’d)

366.8

397.4

315.8

387.2

GC (FW)GC (DW)

264.9

315.9

265.0

315.9

GC+AT (FW)GC+AT (DW)

193.7

214.1

173.3

203.7

GC+AT+R (FW)GC+AT+R (DW)

T5T4T3T2Group

Mean FCR of napier grass for grass carp (GC), grass carp + adult tilapia (GC+AT), and grass carp + adult tilapia + recruits (GC+AT+R) on FW and DW basis.

RESULTS (Cont’d)

CommonAnabaena, Oscillatoria, Detritus, grass / Grass carp feces

Nile tilapia

FrequentCosmarium, Euglena, Brachionus

AllNapier grassGrass carp

RearMoina, Daphnia, Cyclops

FrequencyGut contentsSpecies

Gut contents of grass carp and Nile tilapia of this culture system.

Temperature, pH, DO and Secchi disk depth

0.02.04.06.08.0

10.0

27-May

26-Jun

26-Jul

25-Aug

24-Sep

24-Oct

23-Nov

Date

DO

(mg

/L)

T1 T2 T3 T4 T5

0

50

100

150

27-May

26-Jun

26-Jul

25-Aug

24-Sep

24-Oct

23-Nov

Date

Secc

hi d

isk

dept

h (c

m)

T1 T2 T3 T4 T5

6.0

7.0

8.0

9.0

10.0

27-May

26-Jun

26-Jul

25-Aug

24-Sep

24-Oct

23-Nov

Date

pH

T1 T2 T3 T4 T5

101520253035

27-May

26-Jun

26-Jul

25-Aug

24-Sep

24-Oct

23-Nov

Date

Wat

er te

mpe

ratu

re (o C

)T1 T2 T3 T4 T5

TAN, SRP, Total alkalinity and Chlorophyll_a

0.00.51.01.52.0

27-May

26-Jun

26-Jul

25-Aug

24-Sep

24-Oct

23-Nov

Date

TAN

(mg/

L)T1 T2 T3 T4 T5

0.00.10.20.30.4

27-May

26-Jun

26-Jul

25-Aug

24-Sep

24-Oct

23-Nov

Date

SRP

(mg/

L)

T1 T2 T3 T4 T5

0

100

200

300

27-May

26-Jun

26-Jul

25-Aug

24-Sep

24-Oct

23-Nov

Date

Chl

orop

hyll-

a (m

g/m3 )

T1 T2 T3 T4 T5

0255075

100125150

27-May

26-Jun

26-Jul

25-Aug

24-Sep

24-Oct

23-Nov

Date

Tota

l alk

alin

ity

(mg/

L C

aCO 3)

T1 T2 T3 T4 T5

Diel oxygen fluctuation of Grass carp monoculture treatment on Aug 20, 2002.

Treatment-1

0.00.51.01.52.02.5

0600

h10

00 h

1400

h18

00 h

2200

h02

00 h

0600

h

Time

DO

(mg/

L)

15 cm 45 cm 75 cm105 cm 140 cm

CONCLUSIONSMonoculture of grass carp feeding with napier grass in stagnant system is risky.

Optimal ratio of grass carp to Nile tilapia in polyculture fed with napier grass is 1:1 in this present study.

Addition of Nile tilapia to the grass carp tanks fed napier grass as a sole nutrient input in stagnant water system can efficiently utilize available resources, reuse waste derived from grass carp, enhance total fish yield and also maintains natural balance of pond environment.

Grass carp-Nile tilapia polyculture fed napier grass is a low-cost alternative aquaculture system for small-scale poor farmers which can yield about 4.5 to 5.0 t/ha annually.