Fish conservation in the land of steppe and sky: Evolutionarily significant units of threatened salmonid species in Mongolia mirror major river basins. Issue 6 (27th February 2019)

• Record Type: Journal Article
• Authors: Kaus, Andrew; Michalski, Stefan; Hänfling, Bernd; Karthe, Daniel; Borchardt, Dietrich; Durka, Walter
• Is Part Of: Ecology and evolution. Volume 9:Issue 6(2019)
• Page Start: 3416
• Page End: 3433
• Publication Date: 2019-02-27
• Subjects: Brachymystax lenok -- evolutionarily significant units -- freshwater fish conservation -- Hucho taimen -- threatened salmonids -- Thymallus baicalensis; Ecology -- Periodicals; Evolution -- Periodicals; 577.05
• DOI: 10.1002/ece3.4974
• Languages: English
• ISSNs: 2045-7758

Abstract

Abstract: Mongolia's salmonids are suffering extensive population declines; thus, more comprehensive fisheries management and conservation strategies are required. To assist with their development, a better understanding of the genetic structure and diversity of these threatened species would allow a more targeted approach for preserving genetic variation and ultimately improve long‐term species recoveries. It is hypothesized that the unfragmented river basins that have persisted across Mongolia provide unobstructed connectivity for resident salmonid species. Thus, genetic structure is expected to be primarily segregated between major river basins. We tested this hypothesis by investigating the population structure for three salmonid genera ( Hucho, Brachymystax and Thymallus ) using different genetic markers to identify evolutionarily significant units (ESUs) and priority rivers to focus conservation efforts. Fish were assigned to separate ESUs when the combined evidence of mitochondrial and nuclear data indicated genetic isolation. Hucho taimen exhibited a dichotomous population structure forming two ESUs, with five priority rivers. Within the Brachymystax genus, there were three B. lenok ESUs and one B . tumensis ESU, along with six priority rivers. While B . tumensis was confirmed to display divergent mtDNA haplotypes, haplotype sharing between these two congeneric species was also identified. For T. baicalensis, only a single ESU was assigned, with five priority rivers identified plus Lake Hovsgol. Additionally, we confirmed that T. nigrescens from Lake Hovsgol is a synonym of T. baicalensis . Across all species, the most prominent pattern was strong differentiation among major river basins with low differentiation and weak patterns of isolation by distance within river basins, which corroborated our hypothesis of high within‐basin connectivity across Mongolia. This new genetic information provides authorities the opportunity to distribute resources for management between ESUs while assigning additional protection for the more genetically valuable salmonid rivers so that the greatest adaptive potential within each species can be preserved. Abstract : Mongolia's salmonids are in decline; therefore, genetically valuable populations must be identified so management resources can be prioritized. Across all species, the most prominent pattern was strong differentiation among major basins with low differentiation and weak patterns of isolation by distance within basins corroborating the hypothesis of high within‐basin connectivity. Conservation priority should focus on priority populations within each ESU, where an ecosystem‐based management approach via the establishment of freshwater protected areas should be implemented.