baseline knowledge on the status of marine invasions in this region. This is expected
to provide a solid basis upon which effective evidence-based management will be
developed in the future.
9.1 Introduction
Marine alien species were likely first introduced to southern Africa with the arrival of
European settlers in the early 1600s (Mead et al. 2011a). Despite this long history of
human-associated introductions, the dedicated study of marine invasions along the
South African coast only began in 1992 when the first list of alien species was
produced (Griffiths et al. 1992), detailing the presence of just 15 species. Over the
next decade this list was refined, with some species being removed as initial misidentifications were uncovered, while others were removed as local extinctions were
recorded (Griffiths 2000; Awad 2002). Following international trends, the subsequent decade saw numerous updates to the list of alien species known from the
region (Robinson et al. 2005; Griffiths et al. 2009; Mead et al. 2011a). Notably, the
list was expanded to include cryptogenic species (Robinson et al. 2005) and historical introductions (Mead et al. 2011a). In keeping with international best practice, the
most recent listing of alien marine biota differentiated between alien species (those
whose presence in a region is attributable to human actions) and invasive species
(those alien species that have self-replacing populations over several generations and
have spread from their point of introduction) (Richardson et al. 2011). This saw the
recognition of 89 alien species of which 53 were considered to be invasive (Robinson et al. 2016). Nonetheless, historic invasions continue to be recognised and new
invasions continue to occur. Reflecting this, an additional five alien species [the
intertidal isopod Ligia exotica (Greenan et al. 2018), the Chilean Stone Crab
Homalaspis plana (Peters and Robinson 2018), the South American Sunstar
Heliaster helianthus (Peters and Robinson 2018), the Maritime Earwig Anisolabis
maritima (Griffiths 2018) and the barnacle Perforatus perforatus (CL Griffiths pers.
comm)], as well as two invasive species [the amphipod Caprella mutica (Peters and
Robinson 2017) and the porcelain crab Porcellana africana (Griffiths et al. 2018)]
have been recorded since 2016.
While this increasing trend is typical of many marine ecosystems (Wonham and
Carlton 2005; Galil et al. 2014), the number of alien species known from
South Africa still appears to be much lower than in other well-studied sites. For
example, over 680 alien species are known from the Mediterranean Sea (Galil et al.
2014), while 180 have been recorded in the restricted area of Port Philip Bay,
Australia (Hewitt et al. 2004). Although presently comparatively low, the number
of alien species recognised from along the South African coast is expected to keep
rising. This increasing trend is likely to be sustained by new incursions, but also by
the study of previously under-studied habitats (e.g. kelp beds and temperate reefs),
regions (e.g. large stretches of the East coast) and taxa (especially taxa such as
nematodes and ostracods). Nonetheless, the value of such increased research effort
will depend largely on the availability of taxonomic experts to correctly identify
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T. B. Robinson et al.
to provide a solid basis upon which effective evidence-based management will be
developed in the future.
9.1 Introduction
Marine alien species were likely first introduced to southern Africa with the arrival of
European settlers in the early 1600s (Mead et al. 2011a). Despite this long history of
human-associated introductions, the dedicated study of marine invasions along the
South African coast only began in 1992 when the first list of alien species was
produced (Griffiths et al. 1992), detailing the presence of just 15 species. Over the
next decade this list was refined, with some species being removed as initial misidentifications were uncovered, while others were removed as local extinctions were
recorded (Griffiths 2000; Awad 2002). Following international trends, the subsequent decade saw numerous updates to the list of alien species known from the
region (Robinson et al. 2005; Griffiths et al. 2009; Mead et al. 2011a). Notably, the
list was expanded to include cryptogenic species (Robinson et al. 2005) and historical introductions (Mead et al. 2011a). In keeping with international best practice, the
most recent listing of alien marine biota differentiated between alien species (those
whose presence in a region is attributable to human actions) and invasive species
(those alien species that have self-replacing populations over several generations and
have spread from their point of introduction) (Richardson et al. 2011). This saw the
recognition of 89 alien species of which 53 were considered to be invasive (Robinson et al. 2016). Nonetheless, historic invasions continue to be recognised and new
invasions continue to occur. Reflecting this, an additional five alien species [the
intertidal isopod Ligia exotica (Greenan et al. 2018), the Chilean Stone Crab
Homalaspis plana (Peters and Robinson 2018), the South American Sunstar
Heliaster helianthus (Peters and Robinson 2018), the Maritime Earwig Anisolabis
maritima (Griffiths 2018) and the barnacle Perforatus perforatus (CL Griffiths pers.
comm)], as well as two invasive species [the amphipod Caprella mutica (Peters and
Robinson 2017) and the porcelain crab Porcellana africana (Griffiths et al. 2018)]
have been recorded since 2016.
While this increasing trend is typical of many marine ecosystems (Wonham and
Carlton 2005; Galil et al. 2014), the number of alien species known from
South Africa still appears to be much lower than in other well-studied sites. For
example, over 680 alien species are known from the Mediterranean Sea (Galil et al.
2014), while 180 have been recorded in the restricted area of Port Philip Bay,
Australia (Hewitt et al. 2004). Although presently comparatively low, the number
of alien species recognised from along the South African coast is expected to keep
rising. This increasing trend is likely to be sustained by new incursions, but also by
the study of previously under-studied habitats (e.g. kelp beds and temperate reefs),
regions (e.g. large stretches of the East coast) and taxa (especially taxa such as
nematodes and ostracods). Nonetheless, the value of such increased research effort
will depend largely on the availability of taxonomic experts to correctly identify
230
T. B. Robinson et al.