Evaluation of growth performances of crossbreds and backcrossbreds with purebreds Nishikigoi and Hungarian carp (Cyprinus carpio)

This study aimed to evaluate growth curves among different common carp genotypes, according to fingerling performance and morphometry. Fingerlings selected according to Nishikigoi pattern, either (9.66 ± 1.47) cm in standard length, from crossbred and pure carp, respectively, were cultivated in 8 cages (4 replicates for each genotype), measuring 9 m³ (3.0 m × 2.0 m × 1.5 m) each, in a 1500 m² (12 m × 125 m) pond at a depth of 1.60 m with 10 fingerlings/m³. Fish were fed four times a day at the rate of 5%–7% of biomass with the same specific diet for each growth stage. Forty carp of each genotype (10 fish/cage) were weighed at days 0, 60, 150, 270 and 330 of cultivation. They were weighed and measured for head length, standard length, body height and body width. The Gompertz model was fit for weight × age data for comparison of absolute and relative growth rate, weight and age at the inflection points. The crossbred genotype showed better survival, weight gain and feed conversion compared to pure carp (P < 0.05). The final weight estimate at 330 days was 38.45% higher in the crossbred genotype (289.16 g) when compared to the pure carp (208.85 g). The pure genotype presented lower weight (431.60 g), age (559.71 days) and absolute growth rate (1.03 g/day) at the inflection points when compared to the crossbred genotype (587.69 g; 559.71 days and 1.46 g/day, respectively). Body morphometric relationships changed with fish growth, and this occurred differently, depending on carp genotype evaluated. From these results, it can be concluded that crossing Nishikigoi with Hungarian carp can be a strategy to improve desirable characteristics in koi.