Morphomeristic Characterization of Enteromius Species in Small Water-bodies of the North Rift, Kenya

Abstract

Enteromius, a diverse genus of cyprinid fish native to tropical Africa, comprises around 350 species. These species inhabit various aquatic habitats, notably in Kenya’s North Rift region. Rivers and reservoirs in this area provide essential habitats but face threats from agricultural activities and habitat fragmentation. Morphometric and meristic traits help manage fisheries by offering insights into population dynamics and species identification, although misidentifications pose challenges. Conservation of Enteromius is crucial as these fish support local biodiversity and food security, yet they are increasingly threatened by environmental changes and human activities. The study, conducted in Kenya's North Rift sampled small water bodies, involved sampling 25 rivers and reservoirs impacted by agriculture. Fish were collected from February to July 2018 using electrofishing and seine nets. A total of 972 Enteromius specimens were identified, measured, and analyzed for morphometric and meristic traits. Measurements were taken with Vernier calipers, and 11 meristic counts were recorded. Unidentified samples were preserved for further identification at the National Museums of Kenya. The analysis was performed at UoE Labs following established methodologies. The results indicated that E. paludinosus from Kapsaina Reservoir had the highest standard length (SL) of 8.1±0.8 cm, while E. neumayeri from Ellegrin Reservoir reached 9.4±1.3 cm. Notable differences in operculum length, prepectoral length, prepelvic length, preanal length, and body depth were recorded across different reservoirs and rivers. For instance, Karara Reservoir populations showed the highest operculum length in E. paludinosus (28.2±4.9) and E. neumayeri (25.5±3.2). Meristic traits, such as lateral scales above and dorsal fin rays, also varied significantly, with Kapsaina Reservoir exhibiting the highest range for E. paludinosus. In conclusion, significant trait variations among E. paludinosus, E. apleurogramma, E. neumayeri, and E. cercops across habitats indicate complex genetic and environmental influences emphasizing the need for further research to understand these adaptations and their evolutionary implications