Effect of different stocking density on some growth performance and skin color of Koi carp fry (Cyprinus carpio var. Koi Linnaeus, 1758) reared in concrete, earthen and fiberglass ponds

The aim of this study was to elevate the effect of stocking density of 20, 25 and 30 fish/m3 on some growth parameters and skin color of Koi fry (Cyprinus carpio) with the mean weight of 1.9 ±0.8 g (±SE) in the concrete ponds, earthen ponds, and fiberglass tanks with the total capacity of 1000 L for 45 days. The highest Final weight (12.38±1.9 g), Final length (10.05±1.06 cm), Body weight increase (8.4±1.3g), Body length increase (9.51±1.96 cm), Percent body weight increase (551.57±2.48%), Specific growth rate (2.73±0.05%/day), survival rate (100%) and the lowest Feed conversion ratio (0.74±0.08) were observed in cultured koi fry in concrete ponds at the stocking density of 20 fish/m3 (p<0.05). However, no significant differences between koi fry cultured at stocking density of 20 and 25 fish/m3 in concrete ponds was observed (p>0.05). The results of skin color revealed that the highest level of lightness (56.93±0.03) and the redness color (3.64±0.03) spectrums in Koi fry it was seen in in the concrete tanks at the lowest stocking density and the highest color purity (14.75±1.2), yellow color spectrum (14.31 ± 0.03) and Chroma (20.66±2.09) were observed in concrete tanks at the stocking density of 25 fish/m3. In conclusion, the results of this study indicated that rearing of koi fry in concrete ponds with stocking density of 20-25 fish/ m3 have a positive effect on growth performance, feed efficiency and skin colors of the fish compared to other rearing containers at he similar or higher stock density.