The development of a fish index to assess the biological integrity of South African rivers

Abstract

A biological integrity index that uses attributes of fish assemblages was developed and applied to a part of the Crocodile Rive r (Incomati System, Mpumalanga Province). Fundamentally, the fish assemblage integrity index (FAII) is based on the fish species expected to be present in biological (fish habitat) segments which are sections of river with relatively homogeneous fish habitat. Within this framework fish are categorised according to an intolerance index which takes into account trophic preferences and specialisation, habitat preferences and specialisation, requirement for flowing water during different life-stages and association with habitats with unmodified water quality. This intolerance index, the expected frequency of occurrence and expected health of fish species in a particular fish habitat segment was used to formulate an index for the situation expected under minimally impaired conditions which was used as the comparative basis for the observed (sampled) situation.

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