Distribution of Some Commercially Valuable Fishes (Pangasiidae, Polynemidae, Sciaenidae) in the Mekong Delta (Southern Vietnam) and Role of the Estuaries in Their Life Cycle

Abstract

The composition of the fish population of the Mekong River is one of the richest on the planet, however, despite the high diversity (~1200 species) and productivity, the basis of fishing in the Mekong Delta is made up of several dozen species, the most valuable of which are members of the families Pangasiidae, Polynemidae and Sciaenidae. Information on the distribution of these taxa is fragmentary, and the role of various parts of the delta in their reproduction has not been studied. Distribution of families Pangasiidae, Polynemidae and Sciaenidae in the Mekong Delta was assessed in the dry season by midwater trawl catches in 2019 (April, December), 2021 (January, April) and 2022 (March–May). A total of 237 trawls were carried out, in the catch of which 45.9 thousand fish belonging to 36 families were found. Representatives of each of the families Pangasiidae, Polynemidae, and Sciaenidae were noted in 42–57% of all catches within the studied part of the Mekong Delta, however, the frequency of their occurrence in its various parts varies significantly. According to the Mekong Delta zonation scheme, based on the analysis of the taxonomic composition of the fish population, representatives of Pangasiidae are confined to areas of the upper and middle reaches, Polynemidae—to areas of the middle and lower reaches, while significant differences in the horizontal distribution of Sciaenidae in different parts of the delta have not been identified. Significant differences in the vertical distribution of all studied taxa were also not found. The maximum concentrations of juveniles of Pangasiidae and Polynemidae were found in the middle reaches of the delta, and Sciaenidae in the lower reaches, which indicates the important role of the respective areas in the reproduction of representatives of the studied taxa.