Evidence for population genetic structure in two exploited Mekong River fishes across a natural riverine barrier

Abstract

Impacts of urban development on aquatic populations are often complex and difficult to ascertain, but population genetic analysis has allowed researchers to monitor and estimate gene flow in the context of existing and future hydroelectric projects. The Lower Mekong Basin is undergoing rapid hydroelectric development with around 50 completed and under‐construction dams and 95 planned dams. The authors investigated the baseline genetic diversity of two exploited migratory fishes, the mud carp Henicorhynchus lobatus (five locations), and the rat‐faced pangasiid catfish, Helicophagus leptorhynchus (two locations), in the Lower Mekong Basin using the genomic double digest restriction site‐associated DNA (ddRAD) sequencing method. In both species, fish sampled upstream of Khone Falls were differentiated from those collected at other sites, and Ne estimates at the site above the falls were lower than those at other sites. This was the first study to utilize thousands of RAD‐generated single nucleotide polymorphisms to indicate that the Mekong's Khone Falls are a potential barrier to gene flow for these two moderately migratory species. The recent completion of the Don Sahong dam across one of the only channels for migratory fishes through Khone Falls may further exacerbate signatures of isolation and continue to disrupt the migration patterns of regionally vital food fishes. In addition, H. lobatus populations downstream of Khone Falls, including the 3S Basin and Tonle Sap system, displayed robust connectivity. Potential obstruction of migration pathways between these river systems resulting from future dam construction may limit dispersal, which has led to elevated inbreeding rates and even local extirpation in other fragmented riverine species.

A community‐driven captive‐breeding and reintroduction program maintains genetic diversity in a threatened freshwater fish

“…This finding is consistent with other population genomics studies on the species, which demonstrated lower genetic diversity in upland southern pygmy perch populations (Brauer et al, 2016;Brauer & Beheregaray, 2020;Cole et al, 2016). The levels of genetic diversity observed here are lower than other threatened freshwater fishes (e.g., Biesack et al, 2020;Kajungiro et al, 2019;Skovrind et al, 2016), highlighting the conservation concern for these populations. Relatedly, population-level fitness is often correlated with measures of heterozygosity (Chapman et al, 2009;Kardos et al, 2021;Paige, 2010).…”

Mixed-stock analysis in the age of genomics: Rapture genotyping enables evaluation of stock-specific exploitation in a freshwater fish population with weak genetic structure

“…Genomics is emerging as an influential tool for managing and conserving freshwater fishes globally (Tibihika et al 2020; Biesack et al 2020). In Africa and Asia, genomics has become an important tool to quantify diversity and identify critically endangered populations (Malinsky et al 2018; Ackiss et al 2019).…”

Population Genetic Structure of Ornatus Spiny Lobster (Panulirus Ornatus) in Indo-West Pacific Region

“…Many other marine decapod crustaceans, however, do show strong and significant population structure across the Indo-Pacific, despite their great potential for long-distance larval dispersal such as black tiger shrimp [38], coconut crab [39], and mangrove crabs [40]. Recent scientific evidences also shows an isolated localized subpopulations of commercially exploited species due to overexploitation cause loss of genetic variation [41], [42].…”