Current Status of Fish Species Diversity and Relative Abundance of Beko and Gacheb Rivers, Southwest Ethiopia: Implication for Fishery Opportunity

Ethiopia, a landlocked country, relies on inland waters for fish, a vital low-cost protein source. Its standing water bodies span 7000 km², with rivers extending 8,065 km, supporting diverse aquatic life. The fish production potential is estimated at 94,500 tons per year, with around 200 species, 191 native and 9 introduced, and yet thorough investigation is in need. Despite progress, research on Ethiopian fish diversity remains incomplete due to the country's vast area (1.1 million km²) and limited surveys. Therefore, this study investigated fish species diversity and relative abundance in the Beko and Gacheb Rivers, highlighting implications for sustainable fish production. This study was carried out using cross-sectional observational study, and a total of 193 fish samples were collected during dry (April-May 2017) and wet (October-November 2017) seasons using gill nets with varying mesh sizes. Fish samples were identified to species level using taxonomic keys, and their total length and total weight were measured to the nearest 0.1 cm and 0.1g, respectively. Samples were preserved in 10% formalin and stored at Mizan-Tepi University Zoological-Sciences Laboratory. Relative abundance was determined by diversity indices and well-being of fish species was determined by using Fulton’s condition factor. The study recorded three fish species (<i>Lates niloticus, Lates forskalii,</i> and <i>Oreochromis niloticus</i>), with <i>L. forskalii</i> being the most abundant. Three species from the same family were identified, with a diversity index (H=2.52) indicating higher diversity than reported in other studies. The evenness index showed fair representation of species by individuals. The diversity and abundance indices revealed slight variations between sampling sites, with no dominant species observed, indicating complete evenness. Water quality parameters were within acceptable limits for aquatic life. Fish distribution was influenced by physicochemical factors and human activities, while promising fishery opportunities exist due to the presence of commercially important species, high demand, year-round water availability, and a strong fish market. These findings highlight the need for sustainable resource management and further research on fish biology and socioeconomic aspects.