Condition factor, Length – Weight relationship, and the fishery of Barbus altianalis (Boulenger 1900) in Lakes Victoria and Edward basins of Uganda

Abstract

The condition, fishing effort and environmental parameters signify health of fish populations. This study characterized differences in water quality and fishing effort in the lacustrine and riverine systems of the River Nile, Lake Edward and Kazinga channel in Uganda. One-way Analysis of Variance (ANOVA) was used to test for differences in mean relative condition among populations in the water bodies exposed to different levels of fishing effort and water quality conditions. There were significant differences in the mean relative condition (Kn) of Barbus altianalis between River Nile (mean dif 0.0880, P <0.004) and Lake Edward and between River Nile and Kazinga channel (mean dif. 0.0796, P < 0.001). No significant difference in the mean relative condition between Kazinga channel and Lake Edward (mean diff. 0.0840, P < 0.95). Lake Edward had the highest condition (1.05), while Kazinga channel and River Nile had 1.04 and 0.96 respectively. The relationship between weight and length for each population, obtained by pooling individuals across systems was significant (P < 0.001), the length-weight allometry between the populations was also significantly different (F (2, 237) = 9.73, P < 0.001). River Nile had the highest number of fishers of 311 ± 0.88 while the number of fishers in Lake Edward and Kazinga channel were 75 ± 2.45 and 33 ± 9.12, respectively. Catch rates varied between River Nile (1.92 ± 0.59 Kg boat-1 day-1) and the rest of the systems, 6.20 ± 1.86 and 6.85 ± 1.49 Kg boat-1 day-1 in Lake Edward and Kazinga channel respectively. Water quality varied greatly across all the water bodies. Dissolved oxygen was below the minimum of 5 mgl-1 required for the physiology of freshwater fish. Conductivity was highest in Lake Edward (312 µS cm-1), followed by Kazinga channel and least in River Nile. The consistent variation in condition, fishing effort and water quality, indicates differential selective pressures faced by B. altianalis in the systems and therefore calls for concerted efforts for appropriate management measures.