Fish Index of Biotic Integrity (FIBI) A New Method of Assessing Water Quality in Sri Lankan River Waters

Abstract

A multimetric fish Index of Biotic Integrity (FIBI) was used for the assessment of waterquality in Kelani River in Sri Lanka. The original FIBI was developed for streams in theUnited States Midwest streams by James Karr and present fish index was developed bymaking regional modifications to the original IBI to reflect the fish assemblages and structureof the river system in Sri Lanka. The validity of this modified IBI was determined byexamining the quality of river water using Physico-chemical parameters in upper and lowerreaches of the study area.

An assessment program was carried out in the two sites in upper reach (Kaduwela) and lowerreach (Thotalanga) of Kelani river basin from January to July 2012. Fish assemblages weresurveyed by gill nets. Once fish samples were collected they have been identified, counted,examined for diseases and anomalies, and several other biometrics are applied to evaluatebiotic integrity.

FIBI developed for two sites of the Kelani River is comparable with Water Quality Index(WQI) developed based on selected physico-chemical parameters for the same site. The IBIbased on fish was defined as the average of these 14 metrics after scoring as 1, 3 or 5 by amodified trisection method and five integrity classes were defined. WQI was calculated foreach site based on the results of the tested water quality measurements such as DissolvedOxygen (DO), Biological Oxygen Demand (BOD5), pH from both laboratory and field surveyrecords and determination of the water quality in each site was based on the categorieschosen.

Fish IBI scores for these two sites were highly corresponded with the WQI scores obtainedby tested physico-chemical parameters. Kaduwela site (Score = 28) was ranked as ‘Fair’while the others in Thotanlanga (Score = 40) was ranked as ‘Poor’ for FIBI ranking criteria.By comparing the WQI index, Kaduwela site (57.35) was ranked as ‘Fair’ while Thotanlanga(36.9) was ranked as ‘Poor’. Therefore, in this research project, the developed IBI based onfish clearly showed its potential to assess the water quality of Kelani River while suggestingas a valuable and complementary tool to assess the ecological quality distinguished as goodquality sites from disturbed sites.