22.5.3 Cyprinus carpio (Common Carp)
Cyprinus carpio is a global invader that was introduced to South Africa in the 1850s.
As with many other invasive fishes, it is now ubiquitous throughout the country
(Ellender et al. 2014; Weyl et al. 2020, Chap. 6). It is generally associated with
ecosystem-level impacts such as increased turbidity and disruption of substrates and
aquatic plants through their bottom-feeding behaviour (de Moor and Bruton 1988).
The management of C. carpio is therefore important for ecosystem service protection more than for biodiversity restoration. A number of extirpation projects aimed at
improving ecosystem function have been implemented to date. The Century City
wetland system in Cape Town was treated with rotenone in 2008 to remove
C. carpio and improve ecosystem functioning and water quality. Treatment cost
was estimated at ZAR 100,000 for a once-off treatment and was funded by the
Century City Home Owners Association (D. Ferreira, pers. comm.). Post-treatment
monitoring indicated that C. carpio were reduced to below detectable levels
suggesting that the species had been successfully eradicated (B. Paxton, unpublished
data). Subsequent monitoring detected no C. carpio for 5 years, but they were
detected in very low numbers in 2016. It is not clear whether the individuals found
in 2016 were survivors from the original project (i.e. the extirpation failed) or were
re-introduced subsequently. The project was well-supported by the general public as
well as government stakeholders (e.g. Department of Water and Sanitation), due to a
well-coordinated and comprehensive communication plan and a strong management
presence during the treatment (D. Ferreira, pers. comm.).
In 2017, rotenone treatment of a privately-owned farm dam near Nieuwoudtville,
Northern Cape, removed Cyprinus carpio that posed an invasion risk to the
Oorlogskloof River in a nearby protected area. The project was implemented jointly
by the two provincial departments (CapeNature and the Northern Cape Department of
Environment and Nature Conservation) using DEA: NRM funding. Post-treatment
monitoring indicated that the Cyprinus carpio were successfully removed
(Marr et al. 2019).
22.5.4 Clarias gariepinus (Sharptooth Catfish)
Clarias gariepinus is native to the northern parts of South Africa but several extralimital and invasive populations exist in the Cape Fold Ecoregion (Cambray 2003;
Weyl et al. 2020, Chap. 6). Only one extirpation project has been implemented to
date, but it ultimately failed to achieve extirpation. Following an illegal introduction
of catfish into Grey Dam near Makhanda, the Eastern Cape Nature Conservation
agency, assisted by staff from Rhodes University and Albany museum, treated the
dam with rotenone (Cambray 1995). The project was funded by Makhanda and
while successful extirpation was reported post-treatment, subsequent reinvasion of
this species was reported (Cambray 1995).
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Cyprinus carpio is a global invader that was introduced to South Africa in the 1850s.
As with many other invasive fishes, it is now ubiquitous throughout the country
(Ellender et al. 2014; Weyl et al. 2020, Chap. 6). It is generally associated with
ecosystem-level impacts such as increased turbidity and disruption of substrates and
aquatic plants through their bottom-feeding behaviour (de Moor and Bruton 1988).
The management of C. carpio is therefore important for ecosystem service protection more than for biodiversity restoration. A number of extirpation projects aimed at
improving ecosystem function have been implemented to date. The Century City
wetland system in Cape Town was treated with rotenone in 2008 to remove
C. carpio and improve ecosystem functioning and water quality. Treatment cost
was estimated at ZAR 100,000 for a once-off treatment and was funded by the
Century City Home Owners Association (D. Ferreira, pers. comm.). Post-treatment
monitoring indicated that C. carpio were reduced to below detectable levels
suggesting that the species had been successfully eradicated (B. Paxton, unpublished
data). Subsequent monitoring detected no C. carpio for 5 years, but they were
detected in very low numbers in 2016. It is not clear whether the individuals found
in 2016 were survivors from the original project (i.e. the extirpation failed) or were
re-introduced subsequently. The project was well-supported by the general public as
well as government stakeholders (e.g. Department of Water and Sanitation), due to a
well-coordinated and comprehensive communication plan and a strong management
presence during the treatment (D. Ferreira, pers. comm.).
In 2017, rotenone treatment of a privately-owned farm dam near Nieuwoudtville,
Northern Cape, removed Cyprinus carpio that posed an invasion risk to the
Oorlogskloof River in a nearby protected area. The project was implemented jointly
by the two provincial departments (CapeNature and the Northern Cape Department of
Environment and Nature Conservation) using DEA: NRM funding. Post-treatment
monitoring indicated that the Cyprinus carpio were successfully removed
(Marr et al. 2019).
22.5.4 Clarias gariepinus (Sharptooth Catfish)
Clarias gariepinus is native to the northern parts of South Africa but several extralimital and invasive populations exist in the Cape Fold Ecoregion (Cambray 2003;
Weyl et al. 2020, Chap. 6). Only one extirpation project has been implemented to
date, but it ultimately failed to achieve extirpation. Following an illegal introduction
of catfish into Grey Dam near Makhanda, the Eastern Cape Nature Conservation
agency, assisted by staff from Rhodes University and Albany museum, treated the
dam with rotenone (Cambray 1995). The project was funded by Makhanda and
while successful extirpation was reported post-treatment, subsequent reinvasion of
this species was reported (Cambray 1995).
644
S. J. Davies et al.