22.2 Freshwater Invertebrates
22.2.1 Procambarus clarkii (Red Swamp Crayfish)
While 22 alien freshwater invertebrates have been documented in South Africa
(Picker and Griffiths 2017), and several, particularly snails, are known to have
impacts (e.g. see de Kock and Wolmarans 2008), there is no documentation on
control of these species, aside from the Red Swamp Crayfish (see also Chap. 6).
Procambarus clarkii (the Red Swamp Crayfish) is native to North America but
has been introduced in several African countries, including South Africa (see Weyl
et al. 2020, Chap. 6). This species is important in aquaculture and has invaded parts
of Africa via this pathway. By replacing native crab and snail populations, and
consuming aquatic vegetation, red swamp crayfish exert trophic impacts and may
also have structural impacts in rivers (Jackson et al. 2016). In 1988 this species was
found in one or more dams on a farm in Mpumalanga, and in 1994 a control
operation was undertaken by the provincial nature conservation authority to remove
all P. clarkii from one dam, which was partially drained, and all crayfish were
removed by hand or using dip-nets (Nunes et al. 2017). Unfortunately, this operation
was poorly documented and monitoring data are not available. In a follow-up survey
in 2015 and 2016, Nunes et al. (2017) used sweep nets, electrofishing and trapping,
and established that P. clarkii was still present. No further follow ups have been
conducted since 2016. Procambarus clarkii is listed as a prohibited species in NEM:
BA (RSA 2014) but its presence in the country implies that its listing should be
changed to Category 1a and that the species should be a target for national eradication (Table 22.1).
22.3 Marine Invertebrates
Information on introduced marine species has grown rapidly since the 1990s, when
15 introduced marine organisms were recognised (Griffiths et al. 1992); in 2011 a
comprehensive review and survey identified 85 introduced and 39 cryptogenic
marine organisms (Mead et al. 2011a, b). Currently, 95 introduced marine invertebrates are present in South Africa (Robinson et al. 2020, Chap. 9), although only one
species (described below) has been subjected to control. Recognising the need for
more research and management options for marine species, the Marine Alien and
Invasive Species Working Group has recently been formed to advise on
prioritisation of management of marine invasive species at a national level.
632
S. J. Davies et al.
22.2.1 Procambarus clarkii (Red Swamp Crayfish)
While 22 alien freshwater invertebrates have been documented in South Africa
(Picker and Griffiths 2017), and several, particularly snails, are known to have
impacts (e.g. see de Kock and Wolmarans 2008), there is no documentation on
control of these species, aside from the Red Swamp Crayfish (see also Chap. 6).
Procambarus clarkii (the Red Swamp Crayfish) is native to North America but
has been introduced in several African countries, including South Africa (see Weyl
et al. 2020, Chap. 6). This species is important in aquaculture and has invaded parts
of Africa via this pathway. By replacing native crab and snail populations, and
consuming aquatic vegetation, red swamp crayfish exert trophic impacts and may
also have structural impacts in rivers (Jackson et al. 2016). In 1988 this species was
found in one or more dams on a farm in Mpumalanga, and in 1994 a control
operation was undertaken by the provincial nature conservation authority to remove
all P. clarkii from one dam, which was partially drained, and all crayfish were
removed by hand or using dip-nets (Nunes et al. 2017). Unfortunately, this operation
was poorly documented and monitoring data are not available. In a follow-up survey
in 2015 and 2016, Nunes et al. (2017) used sweep nets, electrofishing and trapping,
and established that P. clarkii was still present. No further follow ups have been
conducted since 2016. Procambarus clarkii is listed as a prohibited species in NEM:
BA (RSA 2014) but its presence in the country implies that its listing should be
changed to Category 1a and that the species should be a target for national eradication (Table 22.1).
22.3 Marine Invertebrates
Information on introduced marine species has grown rapidly since the 1990s, when
15 introduced marine organisms were recognised (Griffiths et al. 1992); in 2011 a
comprehensive review and survey identified 85 introduced and 39 cryptogenic
marine organisms (Mead et al. 2011a, b). Currently, 95 introduced marine invertebrates are present in South Africa (Robinson et al. 2020, Chap. 9), although only one
species (described below) has been subjected to control. Recognising the need for
more research and management options for marine species, the Marine Alien and
Invasive Species Working Group has recently been formed to advise on
prioritisation of management of marine invasive species at a national level.
632
S. J. Davies et al.