Invasion
Invasion Description
The date of first occurrence of Perna perna on the Brazilian Coast is not known, but its absence in prehistoric coastal shell middens indicates that was introduced after European colonization, probably with the African slave trade in the 17th-19th centuries (Souza et al. 2003; de Oliveira et al. 2017). This is contradicted by another which reports that, C14 dating of shells at archaeological sites produced ages of 700-800 years, predatiing European colonization. Genetic analysis indicated that divergence between Brazilian and South African populations ocuorred ~200,000 years BP (Pierri et al. 2016). A later study supports the introduced status, and found that the 'pre-colonial' sites with P. perna sites had been disturbed in recent years, and the occurrence of the mussels probably resulted from contamination. Recalibration of the radiocarbon measurements gives dates of 1448-1801, consistent with introduction thorugh the slave trade (Silva et al. 2018).
Geographic Extent
Rio Grande do Sul, Santa Catarina, Paraná, Rio de Janeiro states/Brazil (Atlantic Ocean) (Siddall 1980; Souza et al. 2003; Silveira et al. 2006); Rio de Janeiro State/Brazil/Ilha Grande Bay (Ignacio et al. 2010); Sao Pauo State/Brazil/São Sebastião Channel (Marques et al. 2013); Cerro Verde/Uruguay/Atlantic Ocean (1st record, 1950s, Carranza and Borthagaray 2009; Schwindt et al. 2020)); lhabela to Niteroi/Brazil/Atlantic Ocean (2016, Oricchio et al. 2019)
Vectors
| Level | Vector |
|---|---|
| Alternate | Hull Fouling |
| Alternate | Dry Ballast |
Regional Impacts
| Economic Impact | Fisheries | |
| Perna perna is extensively harvested from wild populations and reared in aquaculture in Brazil (Souza et al. 2003; da Rocha et al. 2007; de Sa et al. 2007). | ||
| Ecological Impact | Competition | |
| Based on evidence from prehistoric middens, the pearl oyster (Pinctada imbricata) was the dominant bivalve in the rocky intertidal of southern Brazil, before the invasion of P. perna (Souza et al. 2003; Lopez et al. 2010). A Caribbean pearl oyster, Isognomon biolor, introduced in the 1990s, now dominates the mid-intertidal, and overlaps to some extent with P. perna. Competition between P. perna and I. bicolor is suspected (Ferreira et al. 2009). On the Atlantic coast of Uruguay, the smaller native mussel Brachidontes rodriguezii numerically dominated at most sites, but P. perna dominated a shallow subtidal site with intermediate exposure (Carranza and Borthagaray 2009). The authors concluded that the outcome of competition was influenced by complex local factors. | ||
| Ecological Impact | Food/Prey | |
| In intertidal regions of southern Brazil, the introduced P. perna is a major prey item for the native whelks Stramonita sp. and Trachypollia nodulosa, and is preferred over another invader, the Caribbean pearl oyster Isognomon biolor, apparently because of its thinner shell (Lopez et al. 2010). | ||
| Ecological Impact | Habitat Change | |
| Mussel beds of P. perna provide sheltered habitat for a variety of epifauna, particularly amphipods, at both an exposed and a sheltered site near Santos, Brazil (Jacobi 1987). | ||
| Economic Impact | Shipping/Boating | |
| In Brazil, the Navy has to remove fouling (mostly P. perna) from buoys every six months to prevent them from sinking due to the weight of attached organisms (Hicks and Tunnell 1995). | ||