Development and application of a fish-based Sensitivity-weighted Index of Biotic Integrity (SIBI) for use in the assessment of biotic integrity in the Klip River, Gauteng, South Africa

Biotic indices using fish assemblage characteristics have been applied with great success in river assessments around the world. Internationally the most commonly applied fish index is the Index of Biotic Integrity (IBI), whilst in South Africa the most commonly applied index is the Fish Assemblage Integrity Index (FAII). The Sensitivity-weighted Index of Biotic Integrity (SIBI) was developed as an alternative multimetric fish index, incorporating important principles from both the IBI and FAII. This study indicated that the SIBI was a valuable index which used fish as indicators of biotic integrity in the Klip River. The SIBI was also suited to the analysis of site-specific data and the investigation of specific impacts. It is envisaged that the SIBI concept could be applied to other aquatic systems and could possibly be used as an alternative fish index for South African rivers, especially when investigations necessitate site-specific evaluations. The application of the SIBI and IBI in this study also emphasised the FAII's potential underestimation of biotic integrity. The results obtained from the use of the SIBI indicated that the biotic integrity of the Klip River System is currently moderately to critically modified from its natural condition.