Population genetic structure of Antarctic toothfish, Dissostichus mawsoni from Subareas 88 in the Antarctic Ocean based on 21 microsatellite markers

The Antarctic toothfish, Dissostichus mawsoni, serves as a valuable fishery resource around the Antarctic Ocean, which has been managed by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) since 1997. Although defining genetic population structure of this species is crucial for improving fishery management, its number of populations or stocks and genetic diversity levels still remain unclear. In this study, we examined the level of genetic diversity and population genetic structure of the Antarctic toothfish in Subareas 88 by using a combination of the Patagonian toothfish specific (N=7) as well as our developed the Antarctic toothfish microsatellite markers (N=14). The level of genetic diversity in the Subarea 88 tended to be higher in populations from the Ross Sea region MPA (marine protected area) (88.1 RBH, 88.1 RBI, 88.1 RBK, and 88.2 SRZ) than in those from the Amundsen Sea (88.2 RB1, 88.2 RB4, 88.3 RB1, 88.3 RB3, 88.3 RB5). Population structure analyses of 21 microsatellites suggest a well-admixed single gene pool (one genetic stock) in Subareas 88 probably due to high contemporary gene flow during the prolonged epipelagic larval phase of this fish. However, given weak, but significant microsatellite differentiation found between seven population-pairs (88.1 RBK vs. 88.2 RB4, 88.1 RBH vs. 88.2 RB4, 88.1 RBH vs. 88.3 RB1, 88.2 RB4 vs. 88.3 RB1, 88.2 RB4 vs. 88.3 RB3, 88.2 SRZ vs. 88.3 RB1 and 88.3 RB1 vs. 88.3 RB5) implies the possibility of existence of distinct genetic stock or lineages could not be excluded. We further performed preliminary population genomics analysis of this species using our developed approximately ~141,000 SNPs from the obtained sequencing information of an average of 17 Gb per individual to advance our knowledge of the population structure and demographic history of D. mawsoni. The findings of this study will inform conservation efforts on the stock (unit) management for this valuable fishery resource.