Ethiopia has a rich Ichthyo faunal diversity, although they are poorly known. This study was carried out along tributary rivers of Gibe Sheleko National park to identify fish diversity, relative abundance and examine some morphometric measurements. Fishes were collected by using monofilament gillnets and local fishhook, and identified and measured their morphometric by using digital caliper, ruler and digital balance. Of the total ten fish species that were identified, Synodontis schall was the most abundant species (28.52%) followed by Labeobarbus nedgia (18.88%) and Labeobarbus intermediu (14.06%). According to Index of Relative Importance (IRI), S. schall was also first (49.13%) followed by L. intermedius (15.49%) and C. gariepinus. Nevertheless, there were no significance differences between IRI values of fishes (X2= 90.0, df= 81, P= 0.231) and relative abundance between dry and wet seasons (F= 4.51, df= 1, P= 0.048). S. schall had been largest girth (23.1cm), C. gariepinus had largest eye diameter (8.4mm) and body weight (1713.4g),  and Heterobranchus longifilis was first on total, folk and standard length (64.7cm, 64.7cm and 59.8cm, respectively). However, the paired t test of the total body length was not significantly different from the folk length (P>0.005), but statistical different from standard length, weight, and girth (P< 0.005). Gibe River had higher number of species (N) than Wabe River in both seasons. The Shannon diversity index (H') in river of Gibe was also higher (2.09) than Wabe (1.84) during dry, but smallest in wet season (1.52 and 1.57, respectively). Furthermore, as ANOVA test revealed, both (N) and (H') were no difference between tributaries, and seasons (P> 0.005). Generally, differences in sampling habitats, fishing effort and types of gillnet might have contributed to discovered variants findings. Fishery development should be implemented in the park to use the fish resource sustainably.

Keywords: Diversity, Fishery, River, Park