Invasion
Invasion Description
1st Record: Port Elizabeth/South Africa/Indian Ocean (1987, Robinson et al. 2005)
Geographic Extent
Cape Agulhas-Kidds Brach, near East London/South Africa/Indian Ocean (Robinson and Griffiths 2005); South Africa/Plettenberg Bay (Bownes and McQuaid 2006); Tsitsikamma/Southern Ocean (Bownes and McQuaid 2006); Tenza Beach/South Africa/Indian Ocean (2020, Ma et al. 2021, current eastern limit)
Vectors
| Level | Vector |
|---|---|
| Alternate | Fisheries Accidental (not Oyster) |
| Alternate | Hull Fouling |
| Alternate | Ballast Water |
Regional Impacts
| Ecological Impact | Competition | |
| Mytilus galloprovincialis grows faster and has greater reproductive output than the three mussel species native to South Africa, Aulacomya ater, Choromytilus meridionalis, and Perna perna (Branch and Stefanni 2004). Part of this advantage may come from the near-absence of parasites in M. galloprovincialis (Calvo-Ugarteburu and McQuaid 1998). On the south coast of South Africa, the dominant native mussel is Perna perna (Bownes and McQuaid 2006; Nicastro et al. 2007; Zardi et al. 2007). Over a 3-year period, cover and density of M. galloprovincialis increased in the upper intertidal, while P. perna decreased. Cover was lower for M. galloprovincialis in the the lower intertidal than for P. perna, apparently due to higher post-recruitment mortality. The two species appeared to coexist at the two locations (Plettenberg Bay and Tsitsikamma) studied (Bownes and McQuaid 2006). Major factors in this zonation were higher reproductive output in M. galloprovincialis and greater byssus (attachment) strength in P. perna (Zardi et al. 2007). The two species show different strategies in response to wave disturbance, M. galloprovincialis suffering greater mortality due to weaker attachment, but moving more actively as adults and recruiting more rapidly, while P. perna is more likely to survive in place (Nicastro et al. 2008). Food competition does not seem to be important. Stable sioptope and fatty-acid profiles of the two mussels were motly similar (Puccinelli et al. 2017). | ||
| Ecological Impact | Habitat Change | |
| Habitat effects on M. galloprovincialis may be smaller on the south coast than on the west coast of South Africa, since this mussel forms single-layer beds on the south coast, probably due to lower productivity (Phillips 1994, cited by Robinson et al. 2005). | ||
| Economic Impact | Fisheries | |
| Mussels in South Africa have been traditionally important for subsistence harvesting. Mytilus galloprovincialis has increased the available stock, and also created opportunities for aquaculture (Hockey and Van Erkom Schurink 1992). The mussel culture industry in South Africa is based on M. galloprovincialis (Robinson et al. 2005). | ||