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The Effect of Stocking Density on Growth, Survival Rate, and Number of Marketable Fish Produced of Koi Carps, Cyprinus carpio vr. koi in Concrete Tanks

Abstract To test the effect of different stocking densities on their growth, survival rate, and number of marketable fish, advanced larvae (0.14±0.035 g) of koi carp, Cyprinus carpio vr. koiwere cultured for 90 days in 150-L concrete tanks at different densities: 0.1 fish/L (D1); 0.2 fish/L (D2); 0.3 fish/L (D3); 0.4 fish/L (D4); and 0.5 fish/L (D5). There were three replicates for each treatment, where the fish were fed daily, slightly in excess of satiation to eliminate the possibility of food supply being a limiting factor to growth. The D4 and D5 treatments recorded significantly higher (P < 0.05) values of ammonium-N, nitrite-N, nitrate-N, phosphate, and specific conductivity, and significantly lower (P < 0.05) values of dissolved oxygen, compared to the other treatments. Weight gain for koi carps stocked at D1 (7.28 g) was significantly higher (P < 0.05) than that of fish in the other treatments. There was a significant difference in survival rates of koi carps among the treatments ranging from 62.43% in D5 to 93.26% in D1. The number of marketable fish above a set size of 4 g was significantly higher (P < 0.05) in D3, compared to other treatments with higher or lower stocking densities. Therefore, a stocking rate of 0.3 fish/L would be suggested as optimal.