Abundance and fish species composition of both Gerado and Dirma Rivers were studied in dry and wet season from February to November 2014.The objectives of the study were to assess fish species composition, relative abundance and recommend sustainable fishery management to help biodiversity conservation in aquatic ecosystem. Gillnet with mesh size of 6-10 cm were used to catch the fish species, sensitive balance was used to measure weight of the fish in gm and Ruler was used to measure total length of the fish species in cm . Shannon diversity index was used to compare species diversity in both rivers between seasons. Univarate analysis and t test were used to test species composition and abundance difference in both rivers between sites and season through application of SPSS Version 16 .In both rivers , abundance and fish species composition were more in dry season than wet season. The Shannon diversity index(H') value were 1.78 and 1.66 in dry and wet season respectively for Gerdo river and 1.61 and 1.41 in dry and wet season respectively for Dirma River. The dominant fish species in Dirma and Gerado Rivers in dry season was Varcohinus beso with total number of 128 and 129 respectively. The dominant fish species in wet season in Dirma River was Labeobarbus intermedius (40) whereas Varcohinus beso was dominant in Gerado River(25). The total fish species composition of Dirma River was more (6) in dry season than wet season(5).The total fish specimens collected in Drima River was more in dry season (236) than wet season(77).The species composition of Gerado River was higher (8) in dry season than wet season (6).The total fish specimen collected in Gerado River was higher (199) in dry season than wet season(37).There was significant difference in abundance of fish specimens between season and site (P<0.05) un like non-significant variation in Shannon diversity index value (P>0.05) between rivers.
Assefa Tessema, Adem Mohamed