Some aspects of the biology of dominant fishes in blue Nile River, Ethiopia

Abstract

The reproductive biology of dominant fish species below the Tisisat Fall of Blue Nile River was studied during the wet season (September-October, 2010) and dry season (March-April, 2011) using gillnets of stretched mesh size 6, 8, 10 and 12cm, monofilaments of different mesh size, castanet and hook and line. A biotic parameters, temperature, transparency, conductivity, pH and total dissolved solid of the river were taken. A total of 857 fish specimens were collected with the two sampling seasons from all sampling sites. Out of the total catch of specimens four dominant fish species was contributed 79 %. The length weight relationship of L. intermedius, L. forskalii and M. kannume were curvilinear and the relation was statistically significant (P 0.05) in both season and sex however, L. forskalii was statically significant (P< 0.01) in seasons only. Except L. nedgia M. kannume, C. gariepinus and O. niloticus species were collected from the Blue Nile river were significant difference (�T 2 , P<0.05) from the theoretical 1:1 ratio. The relationship between absolute fecundity with FL, TW and Gonad weight of L. intermedius was linear and significant (P<0.05). In general, absolute fecundity of L. intermedius was strongly positively correlated with FL, TW and GW.