extent that most species now only persist in headwater refugia that are isolated from
black bass invasion by the presence of waterfalls (van der Walt et al. 2016). This has
reduced the available habitat for native fishes in the Olifants-Doring River system by
more than 700 km of river (van der Walt et al. 2016). As a result, Micropterus spp.
are typical conflict species that require management interventions that consider both,
economic value and harm to biodiversity (Zengeya et al. 2017).
Bluegill Lepomis macrochirus is a relatively small (maximum mass 1 kg)
centrarchid species often co-introduced as prey for Micropterus spp. Imported
from the USA in 1938, this species has been stocked widely, both through formal
stocking initiatives and illegally by anglers. While this species has established
populations in parts of many major South African River systems, published information about this species in South Africa is limited to a description of its diet
(Ndaleni et al. 2018) and experimental comparisons of its predation efficiency
relative to that of native predatory fishes (Wassermann et al. 2016).
Cyprinidae
Carp-like fishes of the family Cyprinidae in South Africa include Goldfish
C. auratus and the Asian carps: Common Carp C. carpio, Silver Carp H. molitrix
and Grass Carp C. idella, that are among the most invasive fishes globally (Lowe
et al. 2000). Although invasive cyprinids have been associated with a variety of
impacts, including the co-introduction of alien parasites and diseases (e.g. Smit et al.
2017), habitat modifications and competition with native fishes (Ellender and Weyl
2014), surprisingly little research has been conducted on their impacts in southern
Africa (Table 6.1). As cyprinid fishes are well represented in African native fish
faunas, the introduction of novel parasites and diseases by alien cyprinids is a
concern as there are already several examples of spillover to native species (Smit
et al. 2017).
The first documented introduction of a freshwater taxon into South Africa was
C. auratus in 1726 (de Moor and Bruton 1988). This ornamental fish was most likely
introduced from Asia on Dutch trading vessels (de Moor and Bruton 1988). As it is a
popular aquarium fish, C. auratus continues to be imported via the pet trade and fish
are occasionally introduced into the wild by aquarists when they outgrow aquaria, or
accidentally during flooding of ornamental ponds. Although this fish is highly
invasive elsewhere, in South Africa feral populations are rare and generally associated with urban areas. With regard to impacts, C. auratus is associated with the
spread of protozoan, monogean, branchiuran and nematode parasites around the
world, but because these parasites are often associated with other alien fishes, the
direct impact of C. auratus cannot be determined (Smit et al. 2017).
Cyprinus carpio is a large (>1 m in length and 24 kg in mass), brazen gold or
brown fish that is native to Europe and Asia, but has been domesticated as a food fish
for more than 2000 years (Winker et al. 2011). Wild forms are fully-scaled, but
domestic forms include mirror (few scales) and leather (no-scales) variants that were
developed to improve their appeal as a table fish. Cyprinus carpio was first introduced to South Africa from England in 1859 and, as a result of releases into the wild,
now occurs in dams and mainstream rivers of all major river basins in the country. It
6 Alien Freshwater Fauna in South Africa
171
black bass invasion by the presence of waterfalls (van der Walt et al. 2016). This has
reduced the available habitat for native fishes in the Olifants-Doring River system by
more than 700 km of river (van der Walt et al. 2016). As a result, Micropterus spp.
are typical conflict species that require management interventions that consider both,
economic value and harm to biodiversity (Zengeya et al. 2017).
Bluegill Lepomis macrochirus is a relatively small (maximum mass 1 kg)
centrarchid species often co-introduced as prey for Micropterus spp. Imported
from the USA in 1938, this species has been stocked widely, both through formal
stocking initiatives and illegally by anglers. While this species has established
populations in parts of many major South African River systems, published information about this species in South Africa is limited to a description of its diet
(Ndaleni et al. 2018) and experimental comparisons of its predation efficiency
relative to that of native predatory fishes (Wassermann et al. 2016).
Cyprinidae
Carp-like fishes of the family Cyprinidae in South Africa include Goldfish
C. auratus and the Asian carps: Common Carp C. carpio, Silver Carp H. molitrix
and Grass Carp C. idella, that are among the most invasive fishes globally (Lowe
et al. 2000). Although invasive cyprinids have been associated with a variety of
impacts, including the co-introduction of alien parasites and diseases (e.g. Smit et al.
2017), habitat modifications and competition with native fishes (Ellender and Weyl
2014), surprisingly little research has been conducted on their impacts in southern
Africa (Table 6.1). As cyprinid fishes are well represented in African native fish
faunas, the introduction of novel parasites and diseases by alien cyprinids is a
concern as there are already several examples of spillover to native species (Smit
et al. 2017).
The first documented introduction of a freshwater taxon into South Africa was
C. auratus in 1726 (de Moor and Bruton 1988). This ornamental fish was most likely
introduced from Asia on Dutch trading vessels (de Moor and Bruton 1988). As it is a
popular aquarium fish, C. auratus continues to be imported via the pet trade and fish
are occasionally introduced into the wild by aquarists when they outgrow aquaria, or
accidentally during flooding of ornamental ponds. Although this fish is highly
invasive elsewhere, in South Africa feral populations are rare and generally associated with urban areas. With regard to impacts, C. auratus is associated with the
spread of protozoan, monogean, branchiuran and nematode parasites around the
world, but because these parasites are often associated with other alien fishes, the
direct impact of C. auratus cannot be determined (Smit et al. 2017).
Cyprinus carpio is a large (>1 m in length and 24 kg in mass), brazen gold or
brown fish that is native to Europe and Asia, but has been domesticated as a food fish
for more than 2000 years (Winker et al. 2011). Wild forms are fully-scaled, but
domestic forms include mirror (few scales) and leather (no-scales) variants that were
developed to improve their appeal as a table fish. Cyprinus carpio was first introduced to South Africa from England in 1859 and, as a result of releases into the wild,
now occurs in dams and mainstream rivers of all major river basins in the country. It
6 Alien Freshwater Fauna in South Africa
171