Growth, mortality and exploitation rate of Barbus altianalis of River Kuja, Lake Victoria Basin, Kenya.

Abstract

Barbus altianalis is a potamodromous fish that is important for both food and sports fishing. In Kenya, B. altianalis is restricted to the Lake Victoria and its drainage basin. River Kuja is one of the major tributaries draining into Lake Victoria, and limited research has been carried out to pertain the B. altianalis species. There is a history of the decline in B. altianalis abundance and distribution in the Lake Victoria basin. This fish, formerly widely distributed in the Lake and the rivers draining into it, is nowadays mainly confined to the rivers. The analysis was carried out using FiSAT software to assess the condition of the B. altianalis populations such as growth, mortality and exploitation rate. Fish samples were collected from October 2016 to July 2017 using electrofishing equipment from the Kuja River. Length and weight of individual fish were measured, and the total numbers were counted at four different sampling points along the river. Length-frequency data were used to estimate the growth parameters K, L∞ and Z/K using the Powel Wetheral method in the FiSAT software. The asymptotic length, (L∞) and the ratio of the total mortality rate (Z) to the growth constant (K), were estimated to be 54.05 cm TL and 1.717 respectively. The curvature parameter K was estimated as 1.47 yr-1, Z was 2.52 yr-1,and the growth performance index was found to be 3.63. The exploitation, natural and fishing mortalities rates were estimated to be 0.32, 1.71 yr-1 and 0.81 yr-1 respectively. By assessing the asymptotic length calculated, mortalities estimated and exploitation rate found, it is evident that River Kuja has B. altianalis populations. Out of 1239 individuals, 78.05 % were sexually immature, this, therefore, indicates that sustainable management measures be put in place to conserve the young B. altianalis populations.