Some biological aspects of straightfin barb, Enteromius paludinosus (Peters 1852) during the rainy season in Lake Naivasha, Kenya

Abstract

This paper focused on determining the sub lethal effects of reported pollutants in Lake Naivasha, Kenya using the straightfin barb (Enteromius paludinosus), a decade after the existing baseline study. The specific objectives included determining the length–weight relationship (LWR), condition factor (K) and the sex ratio, of the migratory E. paludinosus. A total of 1279 straightfin barb were collected from the mouth of River Malewa, a major source of water for Lake Naivasha using seine nets of mesh size 1.2 mm in the month of November 2017. The fish were caught and transported to the laboratory, then killed humanely by cervical dislocation and thereafter their lengths (cm) and weights (g) determined followed by their dissection to examine the gonads. The length–weight relationship was determined using the formula W = aTLb. The condition factor (K) was determined using the formula K = 100 W/ Lb. A student's t-test was used to test the significant differences in the weight and length of both sexes. The sex ratio, expressed as male: female was calculated by dividing the number of females by that of the males. The equations obtained for the LWR of the combined sexes, males and females of E. paludinosus were, Log W = 3.23 Log L + Log 0.1073, Log W = 2.83 Log L + Log 0.1500 and Log W = 2.87 Log L + Log 0.1522 respectively. The mean condition factor of the combined sex, males and females of E. paludinosus were; 0.5897, 0.5729 and 0.5981 respectively. The sex ratio of the fish was 1: 1.981 (males: females). The results showed that E. paludinosus in Lake Naivasha are not in a good condition, k < 1. The findings of this study may be attributed to the state of the lake due to the reported pollution increase and ecological changes by recent studies. Keywords: Condition factor, Enteromius paludinosus, Lake Naivasha, Length–weight, Sex ratio