Population morphometric variation and condition of Barbus Altianalis (Boulenger 1900) in the River Nile, Lake Edward and Kazinga Channel – Uganda

Abstract

This study used morphometric characteristics and fish condition to compare populations of Barbus altianalis from the River Nile, Lake Edward and Kazinga Channel. Morphological variation was determined using multivariate analysis of advanced truss and non-truss network systems for 251 individuals collected from commercial catches. Fish condition was assessed using relative condition index (Kn) computed using individual fish. Discriminant Function Analysis (DFA) indicated significantly (P≤0.001) higher level of heterogeneity between populations with the two factors (DFA1 and DFA2), collectively accounting for 100% of the variance; (DFA1) 84% and (DFA2) 16%. Group means on the DFA1 showed the River Nile (-0.8869) separated furthest from Lake Edward (0.796) and the Kazinga channel (0.6796). River Nile had the highest number (80.53%) of individuals correctly classified, while Lake Edward (67.2%) and Kazinga channel (60.5%) had more misclassifications between them, an indication they could be much harder to separate. There was a significant difference in mean relative condition among the three habitats (F2, 239 = 9.73, P <0.001, n = 240). The Lake Edward population was in a better condition (1.05) compared to Kazinga Channel (1.04), while the River Nile population had the lowest condition (0.96). Catch rates were higher in Kazinga Channel 6.85±1.49 Kg boat-1 day-1) and Lake Edward (6.20±1.86 Kg boat-1 day-1) and lowest in the River Nile (1.92±0.59 Kg boat-1 day-1). Dissolved oxygen was below the required minimum of 5 mgL-1 in all the water bodies. Conductivity was highest in Lake Edward (312 ±115.78 µS cm-1), followed by Kazinga channel (298.06±131.89 µS cm-1). The observed variations were mainly associated with environmental condition faced by B. altianalis as indicated by water quality and harvest pressure.