Fish biodiversity and its current status in the Mekong river as evidence for developing conservation measures: A case study of the Ba Lai River estuary, Vietnam

The Mekong delta boasts a remarkable fish biodiversity, hosting over 500 recorded species. Among these, the Ba Lai River estuary (BLRE) stands out as one of the most diverse areas in the Mekong delta. This study explored the biodiversity of the fish community in the BLRE, and it assessed its current status. A thorough collection and identification effort conducted from April 2022 to April 2024, encompassing seven sampling sites, resulted in the documentation of 8134 fish individuals representing 188 species, 126 genera, 69 families, and 24 orders. Six species, accounting for 3.19 % of the total, were classified as vulnerable, and one species (0.53 %) was listed as endangered according to the Vietnam Red Data Book and the IUCN Red List; four species (2.13 %) were vulnerable; three species (1.60 %) were near threatened; 18 species (9.57 %) were data deficient, and 125 species (66.49 %) were of least concern. Furthermore, 99 species were migratory fishes (52.66 %); 38 species were endemic to the Mekong River (17.43 %), and 70 species were considered to have local economic value (37.23 %). The Ba Lai River estuary (BLRE) serves as the primary migration route for fish traveling upstream from the sea. However, the area’s fish population has been threatened, leading to a decline in fish biodiversity and stock. Numerous species that were once economically significant now find themselves under threat. Some other species were identified as endemic fishes of the Mekong River, including Pangasianodon hypophthalmus, Pangasius krempfi, Cyclocheilichthys enoplos, and Hemibagrus spilopterus. They have a limited distribution range and are facing threats globally. This study strengthened the protection and conservation of fish fauna in the Mekong estuary and contributed to a deeper understanding of its biodiversity.