Genetic diversity and population structure analysis of blunt snout bream (Megalobrama amblycephala) in the Yangtze River Basin: Implications for conservation and utilization

The blunt snout bream, Megalobrama amblycephala, is a commercially significant freshwater fish species indigenous to China. In recent decades, fishery resources of blunt snout bream in the Yangtze River have been severely depleted owing to human activities, and limited information is available regarding their genetic characteristics. This study aimed to assess the genetic diversity and population structure of different native populations of blunt snout bream in the Yangtze River. We analyzed 222 samples from six natural populations in the middle reaches of the Yangtze River and its affiliated lakes were analyzed using ten microsatellite DNA markers and concatenated sequences of two mitochondrial DNA markers (Cytb and ND2). Microsatellite analysis showed that the average observed heterozygosity (Ho), expected heterozygosity (He), and polymorphic information content (PIC) for all populations were determined as 0.687, 0.739, and 0.748 respectively. Mitochondrial sequence analysis showed that the number of haplotypes (h), haplotype diversity (Hd) and nucleotide diversity (π) of the six populations were 29, 0.768, and 0.00641, respectively. The above findings reveal high genetic diversity within blunt snout bream populations, suggesting a robust potential for selective breeding. The phylogenetic relationship results showed that the six blunt snout bream populations clustered into two branches, indicating a measurable degree of differentiation among the populations in the middle reaches of the Yangtze River Basin and its affiliated lakes. The populations may represent distinct spawning grounds, and corresponding conservation units should be implemented to protect them. In summary, these findings provide vital genetic information for the conservation and commercialization of blunt snout bream in the Yangtze River Basin of China.