Fish biodiversity, distribution and abundance in Iyabe-Riana river, South West Kenya

Abstract

Studies were conducted to establish the distribution, abundance and biodiversity of fish in the Iyabe-Riana River, during the period April-September 2019. Fish samples were obtained from five sampling locations using electro-fisher Samos 1000 producing 75V. Physico-chemical parameters were measured using a YSI hydro lab model 650 MDS. Fish were identified up to genera and where possible up to species level. ANOVA was used to determine significant spatial and temporal differences of fish distribution. The relationship between physico-chemical parameters and fish abundance was determined using Pearson correlation. Shannon-Weiner, Simpson, Margalef and Hill formulae were used to calculate biodiversity, dominance, Richness and evenness indices respectively. Total number of fish decreased from upstream towards downstream. The mean fish catch per hour ranged from 35 ± 18 to 150 ± 67. Analysis of variance showed significant spatial differences in catch rate (p>0.05). Fish abundance was positively correlated with dissolved oxygen concentration while it was negatively correlated with turbidity, total suspended solids and total dissolved solids. Biodiversity, richness and evenness indices were generally higher than in the main River Kuja. Poor water quality observed, affected fish distribution as well as the short-term weather variations. It is concluded that pollution due to anthropogenic activities, short term weather variations and nature of habitat determined fish distribution, abundance and biodiversity.