despite short-term negative effects, the invertebrate community recovered relatively
quickly to pre-intervention levels (Woodford et al. 2013; Bellingan et al. 2015, 2019).
Native fish from upstream of the treatment zone successfully recolonised the treatment
zone, resulting in an increased area of occupancy for these species in the absence of
M. dolomieu (Weyl et al. 2014; Marr et al. 2019).
Despite initial opposition from some stakeholders, perceptions changed considerably during the project from initial scepticism and resistance, to support. This was
largely the result of an independent EIA process prior to treatment, rigorous and
independent scientific monitoring of all aspects of the project such ecological
impacts, project success and treatment regime, and a coordinated and ongoing
media and stakeholder engagement effort.
22.5.2 Oncorhynchus mykiss (Rainbow Trout)
Oncorhynchus mykiss were introduced to South Africa as an angling species in the
late 1890s and are today considered a typical conflict species, i.e. a species with
negative environmental impacts but which is also valuable from a socio-economic
perspective (e.g. for angling and aquaculture) (Woodford et al. 2016; Zengeya et al.
2017; Weyl et al. 2020, Chap. 6). Due to its ability to invade headwaters, O. mykiss is
especially problematic in the Cape Fold Ecoregion and in the high-lying areas of
Mpumalanga and KwaZulu-Natal provinces, all of which are home to a number of
endemic and highly threatened native fishes (e.g. Kleynhans 1987; Skelton 2001;
Shelton et al. 2014; Weyl et al. 2015). Conflict with anglers about the removal of
trout has resulted in a failure to list the species in the NEM:BA Alien and Invasive
Species Regulations (RSA 2016) because of stakeholder opposition (Woodford et al.
2017). Until the impasse on the appropriate management options of O. mykiss is
resolved, the species cannot be regulated under national legislation but is regulated
under provincial conservation ordinances.
Only one control project has been implemented to date, namely a manual
eradication attempt by CapeNature in the Krom River in the Cederberg (Shelton
et al. 2017). The project aimed to remove O. mykiss from the headwaters of the Krom
River, a tributary of the Olifants-Doring system, from 2013 to 2014; extirpation
efforts focused on approximately 6 km of river, and used angling, fyke and gill nets.
A significant reduction in trout numbers was achieved during the attempt, but the
population returned to near its pre-removal abundance level within 2 years. The total
cost of the project was approximately ZAR 150,000 which covered salaries, transport and equipment for the 40-day effort.
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643
quickly to pre-intervention levels (Woodford et al. 2013; Bellingan et al. 2015, 2019).
Native fish from upstream of the treatment zone successfully recolonised the treatment
zone, resulting in an increased area of occupancy for these species in the absence of
M. dolomieu (Weyl et al. 2014; Marr et al. 2019).
Despite initial opposition from some stakeholders, perceptions changed considerably during the project from initial scepticism and resistance, to support. This was
largely the result of an independent EIA process prior to treatment, rigorous and
independent scientific monitoring of all aspects of the project such ecological
impacts, project success and treatment regime, and a coordinated and ongoing
media and stakeholder engagement effort.
22.5.2 Oncorhynchus mykiss (Rainbow Trout)
Oncorhynchus mykiss were introduced to South Africa as an angling species in the
late 1890s and are today considered a typical conflict species, i.e. a species with
negative environmental impacts but which is also valuable from a socio-economic
perspective (e.g. for angling and aquaculture) (Woodford et al. 2016; Zengeya et al.
2017; Weyl et al. 2020, Chap. 6). Due to its ability to invade headwaters, O. mykiss is
especially problematic in the Cape Fold Ecoregion and in the high-lying areas of
Mpumalanga and KwaZulu-Natal provinces, all of which are home to a number of
endemic and highly threatened native fishes (e.g. Kleynhans 1987; Skelton 2001;
Shelton et al. 2014; Weyl et al. 2015). Conflict with anglers about the removal of
trout has resulted in a failure to list the species in the NEM:BA Alien and Invasive
Species Regulations (RSA 2016) because of stakeholder opposition (Woodford et al.
2017). Until the impasse on the appropriate management options of O. mykiss is
resolved, the species cannot be regulated under national legislation but is regulated
under provincial conservation ordinances.
Only one control project has been implemented to date, namely a manual
eradication attempt by CapeNature in the Krom River in the Cederberg (Shelton
et al. 2017). The project aimed to remove O. mykiss from the headwaters of the Krom
River, a tributary of the Olifants-Doring system, from 2013 to 2014; extirpation
efforts focused on approximately 6 km of river, and used angling, fyke and gill nets.
A significant reduction in trout numbers was achieved during the attempt, but the
population returned to near its pre-removal abundance level within 2 years. The total
cost of the project was approximately ZAR 150,000 which covered salaries, transport and equipment for the 40-day effort.
22 Alien and Invasive Animal Control Projects
643