New Hybrid Combination for Local Crucian Carp Germplasm Improvement: Dongting Lake Crucian Carp (♀) × Hefang Crucian Carp (♂).

Due to overfishing, eutrophication of rivers and lakes, and irrational stocking practices, the diversity of wild native carp populations has declined, leading to germplasm degradation and a decrease in fish quality, thereby affecting the sustainable development of fisheries. In this study, a novel hybrid crucian carp lineage (designated LWR) was successfully established via distant hybridization using Dongting Lake crucian carp (LC, ♀) and Hefang crucian carp (WR, ♂) as parental stocks. Systematic analyses were conducted on the morphology, ploidy, fertility, growth performance, survival rate, and molecular genetics of LWR. The results reveal that LWR is an allodiploid (2n = 100), with a chromosome number identical to that of its parents. Gonadal development in the hybrid progeny (LWR) was normal, with both sexes being fertile and reaching sexual maturity at one year of age. Morphologically, LWR exhibited intermediate traits with a paternal bias, characterized by a deep-bodied and elongated shape. In terms of growth performance, LWR displayed significant heterosis (approximately 145% and 271% higher than the body weight of the maternal parent at 6 months and 1 year). Molecular genetic analysis indicated that the 5S rDNA sequences of LWR were predominantly inherited from the paternal parent WR, with insertions, deletions, recombination, and mutations detected. The mtDNA sequences exhibited 99.78% similarity to those of the maternal parent LC, following maternal inheritance with sporadic nucleotide variations. These findings offer a new paradigm for hybridization and a theoretical foundation for the improvement and sustainable utilization of indigenous crucian carp germplasm resources, the selective breeding of improved aquaculture strains, and the sustainable development of fisheries.