The impact of non-native rainbow trout within Afro-montane streams in eastern Zimbabwe
Department of Ichthyology and Fisheries Science, Rhodes University, PO Box 94, Grahamstown, 6140, South Africa; South African Institute for Aquatic Biodiversity, Private Bag 1015, Grahamstown, 6140, South Africa; Department of Biological Sciences, University of Zimbabwe, PO Box MP 167, Mt. Pleasant, Harare, Zimbabwe
Non-native trout species have been associated with many negative effects in receiving ecosystems. The first aim of this study was to determine the impact of non-native rainbow trout Oncorhynchus mykiss on distribution and abundance of native mountain catfish Amphilius uranoscopus within Afro-montane streams in Nyanga Mountains, eastern Zimbabwe. The second aim was to compare macro-invertebrate community responses to the presence of the trout and the catfish. We examined trout impact on catfish's habitat associations, whereas macro-invertebrate composition was compared using open fish and fish exclosure experiments in habitats with and without trout. Trout influenced both the distribution and abundance of the catfish that occupied shallow reaches possibly to avoid predation from trout that occurred in the deeper habitats. Within trout invaded reaches, most macro-invertebrate taxa were more abundant in exclosure than open treatments. By contrast, within trout-free reaches, most macro-invertebrates either did not differ between treatments or were generally more abundant in open than exclosure treatments. This suggests that the macro-invertebrate communities responded differently within invaded and non-invaded reaches. By influencing distribution and abundance of native biota, non-native rainbow trout may have wider ecological effects, such as influencing trophic interrelationships within invaded habitats. © 2013 The Author(s).
abundance; biota; fish; habitat; macroinvertebrate; mountain; predation; stream; Zimbabwe; Amphilius uranoscopus; Invertebrata; Oncorhynchus mykiss; Salmonidae
BES, British Ecological Society