n African Zoology - Preliminary evaluation of the impact of invasive smallmouth bass on native fish abundance in the Witte River, Cape Floristic Region, South Africa - : short communication

Volume 49, Issue 2
  • ISSN : 1562-7020
  • E-ISSN: 2224-073X
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The impact of invasive smallmouth bass, , on the abundance of two native fish species, Breede River redfin, , and Cape kurper, , was investigated in the Witte River tributary of the Breede River in South Africa's Cape Floristic Region (CFR). Native fish density was estimated in five pools and three riffles both above and below a 2 m-high waterfall that acts as a barrier to . Both native species were relatively abundant (mean ± S.E. fish/100 m2: 152.10 ± 19.16-10.33 ± 6.06) at sites above the waterfall where was absent, but absent or scarce (0-0.53 ± 0.38 fish/100m2) at sites below it with . There were no significant differences in measured environmental variables between sites above and below the waterfall, and is thus implicated as the main factor responsible for the differences in native fish densities. These findings highlight the critical role of waterfalls in excluding non-native fishes from native fish refugia in the CFR.

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