Coordinated approaches to rehabilitating a river ecosystem invaded by alien plants and fish
Date
2013-11-27
Journal Title
Journal ISSN
Volume Title
Publisher
Academy of Science of South Africa
Abstract
Large sums have been spent on controlling invasive alien species in South Africa over the past two decades,
but documented accounts of successes are almost non-existent. This brief account describes progress with a
coordinated pioneering project to simultaneously clear invasive alien trees and predatory alien fish from a degraded
but ecologically important river ecosystem in the Cederberg region of the Western Cape Province, South Africa.
Dense infestations of invasive Australian Acacia and Eucalyptus species were cleared over 2 years (2010–2012)
from the riparian zone of the lower reaches of the Rondegat River. This clearance was followed by the local
eradication of an alien fish, smallmouth bass Micropterus dolomieu, from the lower reaches of the river in February
2012 and March 2013 using the piscicide rotenone, so that native threatened fish species could re-colonise from
the upper reaches of the river. Overall costs of the clearance and eradication amounted to nearly R4.5 million,
and early indications are that the native riparian vegetation and fish are recovering well. The project illustrates
several aspects of good practice: careful planning; close and enthusiastic collaboration between affected state
and private landowners; public participation to address concerns; the simultaneous and coordinated application
of mechanical, chemical and biological control of alien plants and chemical control of alien fish; and direction by
qualified ecologists. Although it is too early to assess the long-term success, the exercise provides useful lessons
for such projects elsewhere, and paves the way for the more widespread use of similar approaches in selected
areas that are a priority for conservation.
Description
CITATION: Impson, N. D., Van Wilgen, B. W. & Weyl, O. L. F. 2013. Coordinated approaches to rehabilitating a river ecosystem invaded by alien plants and fish. South African Journal of Science, 109(11/12), Art.
#a0041, doi: 10.1590/sajs.2013/a0041.
The original publication is available at http://sajs.co.za
The original publication is available at http://sajs.co.za
Keywords
Acacia Mearnsii, Micropterus Dolomieu, Biological control, Rotenone, Invasive alien plant species, Alien fish -- Chemical control
Citation
Impson, N. D., Van Wilgen, B. W. & Weyl, O. L. F. 2013. Coordinated approaches to rehabilitating a river ecosystem invaded by alien plants and fish. South African Journal of Science, 109(11/12), Art.
#a0041, doi: 10.1590/sajs.2013/a0041.