Diversity, Relative Abundance and Some Biological Aspects of Fishes in Geba and Sor Rivers, Baro-Akobo Basin, Southwest Ethiopia

Diversity,  relative  abundance  and  some biological  aspects of fishes  in  Geba and  Sor  Rivers  were  studied  using  gill nets (6, 8,  10  and 12cm  stretched mesh sizes)  and  hooks. Samples  of fish were  collected in wet   (October  to  November  2012)   and   dry  (February  to  March   2013) seasons. A total  of 348  fish  specimens  were  collected  from  both  rivers  at both  seasons. Nine fish species were  identified which were  included in six genera and  four  families.  The  represented families  include  Mormyridae, Cyprinidae, Bagridae and  Cichlidae. The  family Cyprinidae was the  most dominant  with  respect  to  number  of  species  consisting  of  six  species (66.7%).  The  diversity of fish species  in  Geba River  (H’=1.50)  was higher than  that of Sor River (H’ =1.10).  The fish diversity of Geba and  Sor Rivers is   less   compared   to   most   studied   Ethiopian   rivers.   Labeobarbus intermedius (60.72%IRI), Labeobarbus nedgia (16.83%IRI) and Labeo cylindricus   (14.66%IRI)   were    the   most  abundant   fish   species.   The abundance of fish specimens in dry season was higher than  in wet season. The   length-weight  relationships  for  these  species   were   found  to   be curvilinear.  The  mean  FCF   for  Labeobarbus  intermedius,  Labeobarbus nedgia and  Labeo  cylindricus were  1.21,  1.02  and  1.21  in Geba and  Sor Rivers,  respectively.  There  was significant  variation  (ANOVA, P<0.05)   in FCF  of Labeo  cylindricus  in  the  two  seasons. However,   variations  were insignificant  (ANOVA, P  >  0.05)   for  the   Labeobarbus  intermedius  and Labeobarbus nedgia in wet and  dry seasons.  In both  rivers females were more    numerous   than    males   and    statistically   significant   (Chi-square, P<0.05).  Further   investigation  on   the   fish  diversity  especially  on   the tributaries of these rivers and  socio-economic aspects of the  two rivers is recommended.