Assessment of Ecosystem Integrity Based on Habitat Quality and Fish Indices of River Kathita and Associated Dams in Upper Tana Basin, Kenya

Abstract

Riverine environments have been threatened by human activities leading to alteration of their biogeochemistry, necessitating an assessment of their ecosystem integrity. River Kathita, in Eastern Kenya, drains into Indian Ocean through River Tana. It is exposed to a variety of anthropogenic activities that affect its habitat quality and integrity. There is limited information on its biota and habitat. This study is therefore designed to bridge this gap and relate how various human activities alter its integrity. A study on assessment of habitat quality and fish index of biotic integrity was conducted on Kathita River and associated dams area in upper Tana basin. Sampling was done for six months (March - August 2020) at eleven stations. Physical-chemical parameters were measured using a YSI multiparameter meter. Total phosphates and nitrates were estimated using the method described in APHA 2014. Nine habitat metrics were assessed and used to develop habitat quality index. Fish samples were collected using an electrofisher, identified to species level and categorized as exotic, indigenous, rheophilic, tolerant or intolerant. Fish diversity was estimated using Shannon-Weiner, Simpson, evenness and species richness indices. Data analysis was done using SPSS and MINITAB versions 22 and 14 respectively. 1133 fish constituting 20 species were caught. Labeobarbus oxhyrinchus was most dominant (24%) while Schilbe intermedius was least (0. 1%). HQI was highest at S1 (21.00 ± 0.730) and lowest at S3 (12.17 ± 0.307). All estimated FIBI were rated ‘below good’, S7 (35.33 ± 2.716, S10 (27.00 ± 1.125). Results from HQI and FIBI shown that the environmental quality of the upper Tana River is degraded. Habitat quality, integrity and biodiversity indices were estimated here for the first time. They form a basis for monitoring environmental quality and integrity in subsequent assessment hence the information will be useful in formulating the environmental conservation and management.