Diversity and Distribution of Fish Species in the Upper Loémé Basin in Mayombe (Republic of Congo, Central Africa)

This study was initiated to document fish species richness and distribution in the upper reaches of the Loémé basin. Carried out between February 2020 and September 2021, sampling targeted eight stations using a standardized gillnetting approach and collected 1356 specimens distributed across 24 species, 18 genera, 9 families, and 5 orders, with the Cyprinidae family (8 species) being the most represented. Species diversity through diversity indices was found to be low, with an unequal distribution of species (H' = 1.54; D' = 0.47; J' = 0.46) at the Bidounzi in Tsessi (TSBI) station where only two species, Enteromius camptacanthus and E. martorelli, dominate; and average in the remaining stations where species are equally distributed (H' > 2; D' J' > 0.5). The Loufouyou gorges constitute a geographic barrier to species dispersal. Brachyalestes kingsleyae, Bryconalestes longipinnis, Chrysichthys auratus, Hemichromis elongatus, Hepsetus lineata and Marcusenius moorii were only sampled in Loémé station in Bilinga (BILO) and Bilinga station downstream from the bridge (BAPO), two stations located downstream of the gorges. This study provides basic knowledge on both species diversity of the upper course of the Loémé basin and the influence of the Loufouyou gorges on their distribution. It also opens up perspectives for future studies of the ichthyological fauna of the latter.