Mitochondrial DNA and Microsatellite Analyses Showed Panmixia between Temporal Samples in Endangered Anguilla japonica in the Pearl River Basin (China)

SIMPLE SUMMARY: The wild resources of Japanese eel (Anguilla japonica) in the Pearl River basin have dramatically declined. Consequently, resource management and conservation of this species are urgently required. By analyzing two mitochondrial fragments (mtDNA) and eight microsatellite markers, we found that nine temporal samples from the Pearl River estuary were not differentiated from each other. In addition, the result of STRUCTURE also supported the conclusion that A. japonica was a panmictic population. Therefore, we suggest that the Japanese eel should be managed as a single unit for conservation. ABSTRACT: The Japanese eel (Anguilla japonica) is a commercially important species in East Asia, the abundance of which has rapidly decreased in recent decades. The fishery resource in the Pearl River basin has mainly deteriorated due to overexploitation and habitat degradation. Knowledge on its genetic status is indispensable for resource management. In this study, we explored the temporal genetic structure of A. japonica on the basis of the concatenated sequences of two mitochondrial fragments (mtDNA) and eight microsatellite markers. A total of nine temporal samples (N = 127) were collected during 2019 and 2021 from Jiangmen City, China, which is located in the Pearl River estuary. mtDNA sequence analysis showed a high level of haplotype diversity, and yielded 124 haplotypes with ranging from 9 to 19 in temporal samples. All microsatellite loci were polymorphic among each of the nine temporal samples, with 150 alleles identified across all samples. Pairwise F(ST) values were low and nonsignificant according to both mtDNA and microsatellite markers. STRUCTURE analysis showed that all temporal samples were not clearly differentiated from each other. The yielded outcomes supported a panmictic pattern in different temporal A. japonica samples. Therefore, our results call for the management of A. japonica as a single unit and joint conservation strategy of the species, since overexploitation in any region will decrease its global resource.