22.5.1 Micropterus Species (Black Basses)
Black Bass is the collective name for species of the genus Micropterus, and four
species (M. salmoides, Largemouth Bass; M. dolomieu, Smallmouth Bass;
M. punctulatus, Spotted Bass and M. floridanus, Florida Bass) have been introduced
into South Africa (Ellender et al. 2014; Weyl et al. 2020, Chap. 6). These species
were introduced for angling and today these fishes are ubiquitous throughout the
country (Ellender et al. 2014). They prey on native fishes and can cause local
extirpations of highly threatened endemic fishes (e.g. van der Walt et al. 2016).
All four species are listed in NEM:BA (RSA 2016) in various categories depending
on their location and are therefore regulated by area. For example, M. dolomieu is
permitted in discrete systems (rivers, lakes, estuaries) where it is established but must
be controlled and wherever possible removed from protected areas and mountain
catchments. Control of Black Bass in tributary streams has been attempted using
manual eradication methods as well as piscicides. Two mechanical extirpation projects have been implemented to date with different outcomes: M. punctulatus was
successfully extirpated from the Thee River in the Cederberg region (van der Walt
et al. 2018), but a similar project aimed at the extirpation of M. dolomieu failed in the
Blindekloof Stream in the Swartkops system (Skelton 1993; Ellender et al. 2011).
Micropterus punctulatus was discovered in 2007 in the Thee River, and
CapeNature’s Invasive Alien Fauna Unit initiated a manual eradication project in
2010 (van der Walt et al. 2018). Removal efforts included netting, spearfishing and
electrofishing as well as the construction of an invasion barrier. Annual surveys from
2015 to 2017 indicated that the population had been successfully extirpated and that
native threatened fish species had recolonised the previously invaded reach of the
river. A total of 442 person days (174 for actual eradication work) were recorded
across all aspects of the project (van der Walt et al. 2018).
Micropterus dolomieu was successfully removed from the Blindekloof River in
1988 by means of angling and electrofishing (Skelton 1993). However, an invasion
barrier was not constructed to prevent reinvasion and management was reliant on
ongoing removal efforts. Management effort was not maintained and M. salmoides
reinvaded the Blindekloof River (Ellender et al. 2011).
Stakeholder conflict and resistance to the two projects described above was largely
absent, as the two bass populations were of low angling value. In contrast, significant
opposition and negative media perception characterised the proposed use of the
piscicide rotenone in the Rondegat River to remove M. dolomieu (Marr et al. 2012).
This project was implemented by CapeNature in 2012–2013 and funded mainly
through the DEA: NRM programme at a cost of approximately ZAR 1.4 million
(Barrow 2014). The project was implemented under the guidance of staff from the
California Department of Fish and Game using Standard Operating Procedures for the
use of rotenone (Finlayson et al. 2010). Micropterus dolomieu were successfully
extirpated from this river following two rotenone treatments 1 year apart and upgrading
of an instream weir to prevent reinvasion from downstream sources (Weyl et al. 2014).
Extensive post-treatment monitoring of non-target aquatic invertebrates illustrated that
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S. J. Davies et al.
Black Bass is the collective name for species of the genus Micropterus, and four
species (M. salmoides, Largemouth Bass; M. dolomieu, Smallmouth Bass;
M. punctulatus, Spotted Bass and M. floridanus, Florida Bass) have been introduced
into South Africa (Ellender et al. 2014; Weyl et al. 2020, Chap. 6). These species
were introduced for angling and today these fishes are ubiquitous throughout the
country (Ellender et al. 2014). They prey on native fishes and can cause local
extirpations of highly threatened endemic fishes (e.g. van der Walt et al. 2016).
All four species are listed in NEM:BA (RSA 2016) in various categories depending
on their location and are therefore regulated by area. For example, M. dolomieu is
permitted in discrete systems (rivers, lakes, estuaries) where it is established but must
be controlled and wherever possible removed from protected areas and mountain
catchments. Control of Black Bass in tributary streams has been attempted using
manual eradication methods as well as piscicides. Two mechanical extirpation projects have been implemented to date with different outcomes: M. punctulatus was
successfully extirpated from the Thee River in the Cederberg region (van der Walt
et al. 2018), but a similar project aimed at the extirpation of M. dolomieu failed in the
Blindekloof Stream in the Swartkops system (Skelton 1993; Ellender et al. 2011).
Micropterus punctulatus was discovered in 2007 in the Thee River, and
CapeNature’s Invasive Alien Fauna Unit initiated a manual eradication project in
2010 (van der Walt et al. 2018). Removal efforts included netting, spearfishing and
electrofishing as well as the construction of an invasion barrier. Annual surveys from
2015 to 2017 indicated that the population had been successfully extirpated and that
native threatened fish species had recolonised the previously invaded reach of the
river. A total of 442 person days (174 for actual eradication work) were recorded
across all aspects of the project (van der Walt et al. 2018).
Micropterus dolomieu was successfully removed from the Blindekloof River in
1988 by means of angling and electrofishing (Skelton 1993). However, an invasion
barrier was not constructed to prevent reinvasion and management was reliant on
ongoing removal efforts. Management effort was not maintained and M. salmoides
reinvaded the Blindekloof River (Ellender et al. 2011).
Stakeholder conflict and resistance to the two projects described above was largely
absent, as the two bass populations were of low angling value. In contrast, significant
opposition and negative media perception characterised the proposed use of the
piscicide rotenone in the Rondegat River to remove M. dolomieu (Marr et al. 2012).
This project was implemented by CapeNature in 2012–2013 and funded mainly
through the DEA: NRM programme at a cost of approximately ZAR 1.4 million
(Barrow 2014). The project was implemented under the guidance of staff from the
California Department of Fish and Game using Standard Operating Procedures for the
use of rotenone (Finlayson et al. 2010). Micropterus dolomieu were successfully
extirpated from this river following two rotenone treatments 1 year apart and upgrading
of an instream weir to prevent reinvasion from downstream sources (Weyl et al. 2014).
Extensive post-treatment monitoring of non-target aquatic invertebrates illustrated that
642
S. J. Davies et al.