Optimizing stocking density for rearing ornamental koi carp in pond cage aquaculture system

The experimental study (90 days) was carried out to optimize the stocking density of ornamental koi carp in pond cage aquaculture system in integration with Indian major carps (IMCs). Koi carp fingerlings were stocked in 15 (5 treatments in triplicate) bamboo net cages (1.0 m³) fixed in earthen pond (380 m²) at stocking densities (fish m⁻³) of20, 40, 60, 80 and 100, whereas, IMCs (catla, rohu and mrigal) were stocked at standard stocking density of 4000 fingerlings acre⁻¹ (380 fish) in ratio of 3:4:3 in earthen pond. Koi carp were fed with commercial feed @ 5% of fish body weight (BW) twice daily and IMCs were fed with formulated pelleted feed @ 1% of BW once daily throughout the experiment. The physico-chemical parameters did not revealed any negative impact of stocking density on water quality. Significantly higher fish survival, growth as well as enhanced feed efficiency in terms of FCR was observed in low stocking density treatments (20 and 40 fish m⁻³). Haematological parameters w.r.t. Hb and Ht increased with maximum value in treatment with 100 fish m⁻³, whereas TLC decreased with minimum value in 60 fish m⁻³, and TEC did not revealed any significantly change. Among biochemical parameters, significant variations were observed for blood serum glucose, total protein and total immunoglobulins, whereas, there were no significant variations in albumin, globulins and A/G ratio. Increase in serum concentration of cortisol, decrease in triiodothyronine and thyroid stimulatinmg hormone and no change in tetraiodothyronine were observed with increasing stocking density. Survival of all the three major carps remained above 90% with impressive growth and FCR. It can be concluded from the present study, that ornamental koi carp can be successfully integrated with carps in pond cage system up to 40 fish m⁻³ for higher economic gain from the available water resource.