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Preliminary evaluation of non-native rainbow trout (Oncorhynchus mykiss) impact on the Cederberg ghost frog (Heleophryne depressa) in South Africa’s Cape Fold Ecoregion

Published in: African Journal of Aquatic Science
Volume 43 , issue 3 , 2018 , pages: 313–318

DOI: 10.2989/16085914.2018.1507898

Author(s): S Avidon Department of Conservation Ecology and Entomology, South Africa , JM Shelton Department of Conservation Ecology and Entomology, South Africa , SM Marr DST/NRF Research Chair in Inland Fisheries and Freshwater Ecology, South Africa , TA Bellingan Centre for Invasion Biology, South Africa , KJ Esler Department of Conservation Ecology and Entomology, South Africa , OLF Weyl DST/NRF Research Chair in Inland Fisheries and Freshwater Ecology, South Africa

Keywords: Amphibian , endemic species , freshwater fish , kick-sampling , Olifants-Doring River Catchment , underwater video analysis , waterfall barrier

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Abstract

We evaluated the impact of non-native rainbow trout Oncorhynchus mykiss on a population of endemic Cedarberg ghost frog Heleophryne depressa in the upper Krom River (Olifants-Doring River Catchment, Cape Fold Ecoregion). We compared H. depressa abundance (using kick-sampling and underwater video analysis) and environmental conditions between sites above and below a waterfall that marks the upper distribution limit of O. mykiss. Heleophryne depressa abundance was significantly greater above the waterfall than that below it, and, because there was no significant difference in measured environmental variables, O. mykiss presence is identified as the most likely explanation for the observed decrease in H. depressa abundance.

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