Spawning migration of Labeobarbus species of Lake Tana to Gilgel Abay River and its tributaries, Blue Nile Basin, Ethiopia

Abstract

Fish samples were collected by using monofilaments gillnets (5-55 mm) and multifilament gillnets, having mesh sizes 
of six, eight, ten, twelve and fourteen centimeter stretched bar mesh, having a length of twenty five meter and depth of 
one and half meter, on six sampling sites of Gilgel Abay River and its tributaries. Dissolved Oxygen, water temperature, 
pH, conductivity, total dissolved solids and water transparency were measured. Samples were collected bimonthly from 
August to October and monthly in November. When all catches are pooled, 89.30% was contributed by the genus 
Labeobarbus and the remaining (5.7%) and (5%) were from the genera Clarias and Varicorhinus, respectively. 
Labeobarbus intermedius was the most dominant (50.10% by number), followed by L. brevicephalus (17.16%) and L. 
nedgia (8.58%). Spatial distribution patterns of the most abundant Labeobarbus species did not show significant 
variation (P >0.05). Temporal segregation among dominant Labeobarbus species was not also evident (P >0.05) except, 
between L. intermedius and L. brevicephalus. All Labeobarbus spp. except L. dainellii, L. gorguari, L. acutirostris and L. 
megastoma were found in all sites. Illegal fishing activities were rampant and must be totally prohibited by closing 
fishing during the spawning months to protect these unique migratory riverine spawning species.