State of the Bay Report 2010-Final - Anchor Environmental

Anchor Environmental
12 ALIEN INVASIVE SPECIES IN SALDANHA BAY-LANGEBAAN
LAGOON
To date, an estimated 85 marine species have been recorded as introduced to South African
waters mostly though shipping activities or mariculture (Mead et al. in prep). At least 62 of these
are thought to occur in Saldanha Bay-Langebaan Lagoon (Table 12.1). Many of these are considered
invasive, including the Mediterranean mussel Mytilus galloprovincialis, the European green crab
Carcinus maenas (Griffiths et al. 1992; Robinson et al. 2005) and the recently detected barnacle
Balanus glandula (Laird and Griffiths, in press). An additional twenty five species are currently
regarded as cryptogenic (of unknown origin – i.e. potentially introduced) but very likely introduced.
Comprehensive genetic analyses are required to determine their definite status, however (Griffiths
et al. 2008).
Most of the introduced species in this country have been found in sheltered areas such as
harbours, and are believed to have been introduced through shipping activities, mostly ballast
water. Because ballast water tends to be loaded in sheltered harbours the species that are
transported originate from these habitats and have a difficult time adapting to South Africa’s
exposed coast. This might explain the low number of introduced species that have become invasive
along the coast (Griffiths et al. 2008).
Future surveys in the Bay will be used to confirm the presence of all listed species and will be
used to ascertain if any additional or newly arrived introduced species are present. Information on
this nature for a newly discovered marine alien species known only from Saldanha Bay and identified
through the State of the Bay monitoring programme is presented below
Table 12.1. List of introduced and cryptogenic species from Saldanha Bay-Langebaan Lagoon. Occurrence
is listed as confirmed or likely (not confirmed from the Bay but inferred from their distribution
in the region). Region of origin and likely vector for introduction (SB = ship boring, SF = ship
fouling, BW = ballast water, BS = solid ballast, OR = oil rigs, M = mariculture, F = Fisheries
activities, I = intentional release) are also listed. (Data from Mead et al. in prep. a & b)
Taxon
PROTOCTISTA
Occurrence
in Saldanha
Bay Origin Vector
Mirofolliculina limnoriae Likely Unknown SB
Zoothamnium sp. Likely Unknown SF
DINOFLAGELLATA
Alexandrium tamarense-complex: Likely N Atlantic/N Pacific BW
Alexandrium minutum Likely Europe BW
Dinophysis acuminata Likely Europe BW
PORIFERA
Suberites tylobtusa Likely Red Sea F
CNIDARIA
Anthozoa
Sagartia ornata Confirmed Europe SF/BW
Metridium senile Likely N Atlantic/N Pacific SF/OR
Hydrozoa
Pachycordyle navis Likely Europe SF/BW
Coryne eximia Likely N Atlantic/N Pacific SF/BW
Pinauay larynx Likely North Atlantic SF/BW
Pinauay ralphi Likely North Atlantic SF/BW
State of the Bay 2010: Saldanha Bay and Langebaan Lagoon 252