Application of the instream flow incremental methodology to Southern African rivers: Protecting endemic fish of the Olifants River

• Published in: Water S. A. Vol. 17; no. 3; pp. 225 - 236
• Main Author: Gore, J.A., King, I.M. & Hamman, K.C.D.
• Format: Journal Article
• Language: English
• Published: Pretoria Water Research Commission (WRC) 01.07.1991; Water Research Commision
• Subjects: Alien fish species; Animal, plant and microbial ecology; Applied ecology; Biological and medical sciences; Endemic fish species; Freshwater; Fundamental and applied biological sciences. Psychology; River flow assessment; South Africa, Olifants River; Southern Africa; Africa; South Africa, Olifants R; Freshwater environment; Vertebrata; Endemic species; Pisces; Stream; Habitat; Cyprinidae; Predation; Animal conservation
• ISSN: 0378-4738

The instream flow incremental methodology (IFIM) has become a recognised technique in the United States for assessing minimum flow requirements of rivers, but is less well known or used elsewhere. The authors have examined the applicability of its software, PHABSIM, in Southern Africa, during a preliminary study of the endemic fish fauna of the Olifants River, Western Cape Province. Despite little change in water quality and flow patterns in the upper mainstream over the last 50 years, most of these fish are now confined to remote headwater tributaries, presumably through the introduction of an alien predator/competitor -- the smallmouth bass, Micropterus dolomieui . It was investigated if, with removal or reduction in numbers of the alien fish species, the endemic fish would still have sufficient physical habitat to re-establish themselves in the mainstream. The simulations have predicted that there is considerable physical habitat available for the endemic fish species in the mainstream and, for some species, more habitat than for the introduced alien.