Inheritance of growth traits in Songpu mirror carp (Cyprinus carpio L.) cultured in Northeast China

Genetic evaluations of candidate traits under special climate conditions could provide effective suggestions for breeding programs of domesticated fish species. Here, we evaluated the genetic parameters for growth traits in Songpu mirror carp (Cyprinus carpio L.) cultured in Northeast China where overwintering of similar to 5 months per year has a great impact on the growth improvement of common carp. Six growth traits of 1096-1153 F-1 progeny were estimated from 36 full-sib families at ages 145 (before overwintering), 332 (after overwintering) and 392 (2 months after overwintering) days. Of particular interest was the overwintering weight loss rate (WLR), which was estimated as a growth-related trait at 332 days of age. No significant sex effect was detected for each trait (P > 0.05). Heritabilities were moderate (0.2-0.4) for body weight (BW), standard length (SL), condition factor (K), relative body height (RBH), and WLR, while they were low (< 0.2) for relative body width (RBWI) and relative head length (RHL). Genetic and phenotypic correlations were strong and positive between BW and SL (r(P) and r(G) > 0.9) at each detecting period. Furthermore, genetic correlations were high between BW145 and BW332 (0.98) but low between BW145 and BW392 (0.29) and between BW332 and BW392 (0.27). Notably, there was a strong and negative genetic correlation between WLR332 and BW392 (- 0.76). The results support that traditional selection based on BW at the beginning or end of the first overwintering period may be unreasonable for Songpu mirror carp in the northeast regions. The WLR is heritable and selection for reduced WLR332 should gradually enhance growth performance in the next culture stage in the present population.