recreational fishery that makes considerable economic contributions through equipment and tourism-related expenditure (Weyl and Cowley 2015).
Most widespread is M. salmoides, which can attain weights of more than 4 kg in
South Africa (Weyl et al. 2017a, b). As is the case with other members of the genus,
M. salmoides is an aggressive predator, first on invertebrates as juveniles, becoming
more piscivorous as adults (de Moor and Bruton 1988). Its reproduction includes the
construction and defence of shallow-water nests in spring with males guarding eggs,
larvae and fry. As a result of its affinity for vegetated still waters, it is common in
slower sections of all larger rivers and in impoundments (Khosa et al. 2019).
Micropterus floridanus was until relatively recently, considered a subspecies of
M. salmoides because the two species are difficult to distinguish morphologically
and because they hybridise when their ranges overlap (Hargrove et al. 2019).
Micropterus floridanus is better adapted to warmer climates than M. salmoides
(Philipp and Whitt 1991), where it has a longer spawning season (Rogers et al.
2006), lives longer and attains larger sizes than Largemouth Bass (Neal and Noble
2002). Its introduction into southern Africa in 1980, resulted in the increase of the
angling record for “Largemouth Bass” that had remained stable at ca. 4.2 kg for more
than 50 years, to 8.3 kg in Zimbabwe in 2004 (Weyl et al. 2017a, b) and 7.1 kg in
South Africa in 2018 (O. Weyl, unpubl. data). Morphological similarity to
M. salmoides and the generally unreported nature of introductions following the
cessation of government support to stocking programmes in the early 1990s
(Ellender et al. 2014) have resulted in a paucity of knowledge on the extent of
spread of this species (Weyl et al. 2017a, b). Recent genetic assessments of
Micropterus species sampled from 20 South African reservoirs demonstrated that
M. floridanus is not only widespread, but is also expanding its distribution (Weyl
et al. 2017a, b; Hargrove et al. 2019).
Two other Micropterus species were imported to fill gaps between the highaltitude trout waters and the slow-flowing, lower-lying M. salmoides zone.
Micropterus dolomieu, which have an affinity for flowing water, were introduced
from the USA in 1937 and M. punctulatus in 1939 for stocking in rivers too turbid to
suit M. dolomieu (see Ellender et al. 2014). Although not as widespread as
M. salmoides and M. floridanus, M. dolomieu and M. punctulatus have invaded
parts of many river systems in the Eastern and Western Cape (Khosa et al. 2019).
Micropterus spp. have had deleterious impacts on native fish and invertebrate
species (see Ellender and Weyl 2014; Ellender et al. 2014 for reviews). Most severe
are the impacts on native minnows that have not coevolved with native predatory
fishes (Ellender et al. 2018). For example, in the Olifants River system in the
Western Cape, predation has fragmented native minnow populations to such an
Fig. 6.6 (continued) (l) Oreochromis niloticus; (m) Oreochromis aureus; (n) Perca fluviatilis;
(o) Gambusia affinis; (p) Poecilia reticulata; (q) Xiphophorus hellerii; (r) Pterygoplichthys
disjunctivus (adapted from Skelton and Weyl 2011; Marr et al. 2018; Khosa et al. 2019)
170
O. L. F. Weyl et al.
Most widespread is M. salmoides, which can attain weights of more than 4 kg in
South Africa (Weyl et al. 2017a, b). As is the case with other members of the genus,
M. salmoides is an aggressive predator, first on invertebrates as juveniles, becoming
more piscivorous as adults (de Moor and Bruton 1988). Its reproduction includes the
construction and defence of shallow-water nests in spring with males guarding eggs,
larvae and fry. As a result of its affinity for vegetated still waters, it is common in
slower sections of all larger rivers and in impoundments (Khosa et al. 2019).
Micropterus floridanus was until relatively recently, considered a subspecies of
M. salmoides because the two species are difficult to distinguish morphologically
and because they hybridise when their ranges overlap (Hargrove et al. 2019).
Micropterus floridanus is better adapted to warmer climates than M. salmoides
(Philipp and Whitt 1991), where it has a longer spawning season (Rogers et al.
2006), lives longer and attains larger sizes than Largemouth Bass (Neal and Noble
2002). Its introduction into southern Africa in 1980, resulted in the increase of the
angling record for “Largemouth Bass” that had remained stable at ca. 4.2 kg for more
than 50 years, to 8.3 kg in Zimbabwe in 2004 (Weyl et al. 2017a, b) and 7.1 kg in
South Africa in 2018 (O. Weyl, unpubl. data). Morphological similarity to
M. salmoides and the generally unreported nature of introductions following the
cessation of government support to stocking programmes in the early 1990s
(Ellender et al. 2014) have resulted in a paucity of knowledge on the extent of
spread of this species (Weyl et al. 2017a, b). Recent genetic assessments of
Micropterus species sampled from 20 South African reservoirs demonstrated that
M. floridanus is not only widespread, but is also expanding its distribution (Weyl
et al. 2017a, b; Hargrove et al. 2019).
Two other Micropterus species were imported to fill gaps between the highaltitude trout waters and the slow-flowing, lower-lying M. salmoides zone.
Micropterus dolomieu, which have an affinity for flowing water, were introduced
from the USA in 1937 and M. punctulatus in 1939 for stocking in rivers too turbid to
suit M. dolomieu (see Ellender et al. 2014). Although not as widespread as
M. salmoides and M. floridanus, M. dolomieu and M. punctulatus have invaded
parts of many river systems in the Eastern and Western Cape (Khosa et al. 2019).
Micropterus spp. have had deleterious impacts on native fish and invertebrate
species (see Ellender and Weyl 2014; Ellender et al. 2014 for reviews). Most severe
are the impacts on native minnows that have not coevolved with native predatory
fishes (Ellender et al. 2018). For example, in the Olifants River system in the
Western Cape, predation has fragmented native minnow populations to such an
Fig. 6.6 (continued) (l) Oreochromis niloticus; (m) Oreochromis aureus; (n) Perca fluviatilis;
(o) Gambusia affinis; (p) Poecilia reticulata; (q) Xiphophorus hellerii; (r) Pterygoplichthys
disjunctivus (adapted from Skelton and Weyl 2011; Marr et al. 2018; Khosa et al. 2019)
170
O. L. F. Weyl et al.