INCLUSION OF NILE TILAPIA Oreochromis niloticus AND SAHAR Tor putitora IMPROVES RODUCTIVITY IN CARP-POLYCULTURE SYSTEM Madhav K. Shrestha, AFU Nepal Rama N. Mishra, DoFD Nepal Mahendra Bhandari, AFU Nepal James S. Diana, UM USA Asian Pacific aquaculture 2016 (26-29 April), Surabaya Indonesia

Introduction Aquaculture is the one of the fastest growing food producing sector in Nepal for the last 5-6 years with a growth rate of 8.4% per annum. Pond area has increased from 6500 ha to 9200 ha during last 6-7 years. Pond aquaculture is the major aquaculture system contributing more than 95% of total aquaculture production. Semi-intensive carp polyculture is the established and commonly practiced system and carps contributes about 90% of the production.

Introduction (Contd.) Besides carps, rainbow trout, African catfish, tilapia, pangasius catfish has been initiated in culture with limited volume of production. Mostly the increase in production is from expansion of the area. Intervention in carp polyculture system to increase productivity might be the best option to make big production increment. AquaFish research has developed mixed-sex tilapia culture system with sahar (Tor putitora) to small farmers. Further more, sahar is a popular indigenous species which needs due attention to conserve and Nile tilapia is a government recommended species for commercial aquaculture.

Inclusion of tilapia and sahar in carp polyculture system might be a small intervention but significant growth in aquaculture production if it increases productivity. Objectives: To increase pond productivity through species diversification; To assess the productivity of carp polyculture system with adding tilapia and tilapia-sahar species. To develop partial enterprise budgets of costs and values of fish crops in different polyculture systems.

Materials and Methods Two experiments were conducted. First on-station experiment at the Fisheries Development Center, Bhairahawa (Government Fish Farm) Experimental units: 9 earthen ponds of 200 m 2 Experimental period: 240 days (9 August 2014 to 9 May 2015) Treatments in triplicates: a) Carps only or control (10000 fish/ha) (T 1 ) b) Carps (10000/ha) + tilapia (3000/ha) (T 2 ) c) Carps (10000/ha) + tilapia (3000/ha) + sahar (1000/ha) (T 3 )

Materials and Methods (Contd.) Species combination and ratio for carp polyculture (government recommended): Silver carp (35%) Bighead carp (10%) Common carp (25%) Grass carp (5) Rohu (15%) Mrigal (10%) Pond preparation: Ponds were completely drained and treated with lime at 10.0 kg per 200 m 2 pond. Sun dried for 3 days and filled the water.

Materials and Methods (Contd.) Fertilized pond with di-ammonium phosphate (DAP), urea and farm yard manure (FYM) as a basal dose of 7 days. DAP and urea were used at 700 and 940 g, respectively and FYM 60 kg at for the 200 m 2 pond area. Fingerlings were stocked one week after pond fertilization. Weekly fertilization with DAP and urea at 0.4 g N and 0.1 g P m -2 day -1 Feeding with locally made mass feed (20% CP) made from 1:1 mustard oil cake and rice bran at 2% of fish biomass per day.

Materials and Methods (Contd.) Pond water quality – temperature, dissolved oxygen, pH and Secchi disk depth were monitored monthly. Pond fish sampling were performed monthly for fish growth measurement, biomass calculation and feed adjustment. Ponds were completely drained for final harvest and all fish were counted and weighed.

Materials and Methods (Contd.) Second on-farm trial was conducted in farmer’s ponds in Dayanagar village of Rupendehi district. Twelve individual farmers ponds of 380 – 930 m 2 were selected. Two treatments were compared with 6 replicates. a)Carps only or control (10000 fish/ha) b)Carps (10000/ha) + tilapia (3000/ha) + sahar (1000/ha) Trial was conducted for 165 days (10 July to 24 December 2015).

Materials and Methods (Contd.) Carps stocking combination and ratio is similar to above as of government recommenda tion. The ponds were fertilized weekly with urea and di- ammonium phosphate at 0.4 g N and 0.1 g P m -2 day -1. Fish were fed once daily with locally made pellet feed (1:1 rice bran and mustard oil cake; 20% CP) at 2% body weight. Water quality- temperature, DO and pH were measured monthly. Fish sampling were done monthly for growth trend and feed adjustment.

Results On-station experiment at Government Fish farm

Production comparison between treatments (mean ± SE) ParametersTreatments Carps only (T1) Carps + tilapia (T2) Carps+tilapia+sahar (T3) Extrapolated GFY (t/ha/yr) Carps3.13±0.26 a 3.02±0.15 a 3.33±0.12 a Tilapia-0.49±0.05 a 0.45±0.02 a Sahar--0.14±0.02 Combined3.13±0.26 b 3.51±0.20 ab 3.93±0.16 a

Production comparison between treatments (Contd.) Parameters Treatments Carps only (T1) Carps + tilapia (T2) Carps + tilapia + sahar (T3) Extrapolated GFY (t/ha/yr) With recruits 3.13±0.26 b 3.72±0.22 ab 4.04±0.15 a Extrapolated NFY (t/ha/yr) 3.05±0.26 b 3.57±0.25 ab 3.93±0.15 a AFCR 2.53±0.24 a 2.62±0.17 a 2.41±0.11 a Survival (%) 81.2±5.1 a 76.0±3.0 a 80.5±1.3

Tilapia recruits (per pond) SizeParameterT2T3 Small (2-3 cm) Total count Total wt. (kg) Mean wt. (g) 1.66± ±0.06 Large (6-10 cm) Total count Total wt. (kg) Mean wt. (g)22.9 ± ±1.3

Mean pond water temperature

Mean pond water pH

Mean DO

Sechhi disk depth

Gross margin (USD/pond) ParticularscarpsCarps + tilapiaCarps + tilapia + sahar Total input45.01±0.21 b 53.50±2.12 a 55.07±0.58 a Total output71.00±6.53 b 84.87±5.76 ab ±4.80 a Gross margin24.90±6.32 b 31.37±3.54 ab 47.15±4.22 a Gross margin/ha1300±316 b 1570±177 ab 2357±211 a

Gross margin (NRs/pond)

On-farm trial at Farmers pond

Production Comparison between treatments ParametersTreatment Carps only (T1) Carps + tilapia + sahar (T2) GFY (t·ha -1 ·crop -1 )2.2±0.1 b 2.9±0.4 a NFY (t·ha -1 ·crop -1 )2.1±0.1 b 2.8±0.4 a GFY (t·ha -1 ·yr -1 )4.4±0.2 b 5.8±0.8 a NFY (t·ha -1 ·yr -1 )4.2±0.2 b 5.6±0.8 a Survival (%)74.0±2.4 b 89.9±2.3 a AFCR2.6±0.4 a 2.2±0.3 a

Water Quality ParametersTreatment Carps only (T1) Carps + tilapia + sahar (T2) Temperature ( o C) 28.3±2.6 (21.0 – 34.5) 27.4±2.4 (21.3 – 35.1) DO (mg. L -1 ) 3.4±0.2 (1.4 – 5.1) 3.4±0.2 (0.3 – 6.7) pH 7.5 (7.0 – 8.3) 7.6 (7.1 – 9.0)

Gross margin (USD/500 m 2 pond) ParametersTreatment Carps only (T1) Carps + tilapia + sahar (T2) Total input118.0± ±5.0 Total output208.0± ±22.3 Gross margin90.0±12.5 b 161.0±18.4 a Gross margin/ha1800±250 a 3219±367 a

Nile tilapia Grass carp

Common carp Silver/Bighead carp

Conclusions Adding Nile tilapia and sahar did not affect the growth and production of carp species. Adding these species increased total fish productivity. Problem of tilapia recruitment can be addressed partial by the introduction of sahar in polyculture. Nile tilapia and sahar can be added in carp polyculture ponds without affecting the productivity of carp species. The on-station experiment showed 25.5% increase in yield and in on-farm trial with six farmers showed 33.3% increase with this new production system. This is predicted to result in an 81% increase in gross margin for carp-tilapia-sahar polyculture treatment. On-farm trials showed similar results of 78% increase in gross margin