V. germanica is marginally suitable for the species, but if they are able to spread into
the eastern coastal strip of South Africa they could potentially occupy a much larger
climatically suitable range in the sub-tropical regions of the country (Tribe and
Richardson 1994; Veldtman et al. 2012). De Villiers et al. (2017) have indicated
that agricultural irrigation can extend the area of suitable climate for V. germanica,
increasing the chance of this species spreading to the east of the country. Veldtman
et al. (2012) assert that eradication of V. germanica is only possible with continued
systematic control efforts.
The situation regarding P. dominula is more challenging due to the large
populations already present. From the eradication trial it is clear that P. dominula
is well established even at its range edge and containment would require substantial
resources to be effective. However in New Zealand, where V. germanica has
completely infiltrated and taken over native ecosystems, the use of technological
methods such as gene drive (where RNA-guided gene drives—based on CRISPR/
Cas9—are used to modify individuals that are then released to interfere with the
reproduction of the invasive population) are being investigated as a means of
eradicating their population (Lester and Beggs 2019). South Africa would benefit
if New Zealand succeeds in applying and sharing this technology to develop a
potential control method for P. dominula. Currently P. dominula occurs in most
major towns of the Boland region. There are however high volumes of agricultural
produce and equipment being moved between invaded and uninvaded areas which
makes further spread via the Transport—Stowaway pathway (Convention on Biological Diversity 2014) likely.
22.5 Freshwater Fish
In South Africa, 27 alien freshwater fish taxa have been introduced into the wild and
16 of these are considered invasive (Ellender and Weyl 2014). Attempts to control
alien fish have been restricted to a few catchments and species. While this indicates
some progress in the management of invasive fish, the majority of invasive
populations have not been subjected to control, and some control operations meet
much resistance due to the recreational and subsistence value of certain species
(Zengeya et al. 2017).
The formal management of alien fishes for biodiversity restoration was initiated
in 2000 through the Cape Action for People and the Environment project (CAPE;
Younge and Fowkes 2003). The CAPE project defined criteria for identifying rivers
for fish control, subsequent identification of candidate rivers and identification of
suitable eradication methods (Marr et al. 2012) within the Cape Fold Freshwater
Ecoregion (Abell et al. 2008). The outcomes of the control projects are summarised
below.
22 Alien and Invasive Animal Control Projects
641
the eastern coastal strip of South Africa they could potentially occupy a much larger
climatically suitable range in the sub-tropical regions of the country (Tribe and
Richardson 1994; Veldtman et al. 2012). De Villiers et al. (2017) have indicated
that agricultural irrigation can extend the area of suitable climate for V. germanica,
increasing the chance of this species spreading to the east of the country. Veldtman
et al. (2012) assert that eradication of V. germanica is only possible with continued
systematic control efforts.
The situation regarding P. dominula is more challenging due to the large
populations already present. From the eradication trial it is clear that P. dominula
is well established even at its range edge and containment would require substantial
resources to be effective. However in New Zealand, where V. germanica has
completely infiltrated and taken over native ecosystems, the use of technological
methods such as gene drive (where RNA-guided gene drives—based on CRISPR/
Cas9—are used to modify individuals that are then released to interfere with the
reproduction of the invasive population) are being investigated as a means of
eradicating their population (Lester and Beggs 2019). South Africa would benefit
if New Zealand succeeds in applying and sharing this technology to develop a
potential control method for P. dominula. Currently P. dominula occurs in most
major towns of the Boland region. There are however high volumes of agricultural
produce and equipment being moved between invaded and uninvaded areas which
makes further spread via the Transport—Stowaway pathway (Convention on Biological Diversity 2014) likely.
22.5 Freshwater Fish
In South Africa, 27 alien freshwater fish taxa have been introduced into the wild and
16 of these are considered invasive (Ellender and Weyl 2014). Attempts to control
alien fish have been restricted to a few catchments and species. While this indicates
some progress in the management of invasive fish, the majority of invasive
populations have not been subjected to control, and some control operations meet
much resistance due to the recreational and subsistence value of certain species
(Zengeya et al. 2017).
The formal management of alien fishes for biodiversity restoration was initiated
in 2000 through the Cape Action for People and the Environment project (CAPE;
Younge and Fowkes 2003). The CAPE project defined criteria for identifying rivers
for fish control, subsequent identification of candidate rivers and identification of
suitable eradication methods (Marr et al. 2012) within the Cape Fold Freshwater
Ecoregion (Abell et al. 2008). The outcomes of the control projects are summarised
below.
22 Alien and Invasive Animal Control Projects
641