Author(s): Mohammad Saddam Hussain and Chaudhary Nagendra Ray Yadav

Abstract: An experiment in carp polyculture was conducted at Regional Agricultural Research Station, Parwanipur, Bara, Nepal for a culture period of six months (1^st December 2014 to 31^st May 2015) in a completely randomized design with five treatments (T1, T2, T3, T4, and T5) replicated thrice in 15 research units of 100 m² each. Silver carp, bighead carp, rohu, mrigal and common carp were used as stocking materials in all the treatments @ 0.4, 0.2, 0.3, 0.05 and 0.05 fish/m² respectively. Grass carp was used @ 0.0, 0.1, 0.2, 0.3, 0.4 fish/m² in T1 (Control), T2, T3, T4 and T5 respectively. Fertilization was performed biweekly with urea and di-ammonium phosphate @ 0.4g N/m²/day and 0.1 g P/m²/day. Supplementary feed (mustard oil cake and rice bran) was supplied @ 2% body weight of common carp and mrigal. Chopped fresh para grass was provided @ 20% body weight of grass carp. The water quality parameters were within suitable range for fish culture. Extrapolated net fish yield (t/ha/yr) was found the greatest in T5 (2.98±0.07) among all treatments. T3 (2.79±0.18) and T4 (2.72±0.23) were significantly different from T1 (2.04±0.14) (p<0.05), while T2 (2.58±0.09) was not significantly different from T1 (p>0.05). However, benefit cost ratio (B/C) was found the highest in T3 (2.86±0.17) among all treatments which was significantly different from T1 (2.20±0.11) (P<0.05) but not significantly different from T2 (2.62±0.18), T4 (2.68±0.21) and T5 (2.79±0.02) (p>0.05). The inclusion of grass carp reduced food conversion ratio of common carp and mrigal (1.59±0.11) in T3 as compared to T1 (2.07±0.48), which indicated that the excreta of grass carp acted as a source of feed for bottom feeders too. The result of this experiment indicated that grass carp stocked at 0.2 fish/m² (T3) in carp polyculture proved a more profitable and cost effective than rest all the treatments.

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