Invasion
Invasion Description
1st Record: Marennes-Oleron/Bay of Biscay (1966, Grizel and Heral 1991; Bertrand 2018)
)
(We are excluding much earlier introductions of CM angulata
Geographic Extent
Brittany/France/Bay of Brest; Aber Benoit (Brittany)/France/English Channel; Marennes-Oleron/Bay of Biscay (1966, Grizel and Heral 1991, natural settlement by 1975; 2010; 2013, Bishop et al. 2015b); La Rochelle/France/Bay of Biscay (Grizel and Heral 1991, natural settlement by 1975); France/Bay of Bourgenuf (Dutertre 2009, feral oysters became abundant after 1995); continuous on coast of Brittany/France/Atlantic Ocean (Stiger-Pouvreau and Thouzeau 2015)
Vectors
| Level | Vector |
|---|---|
| Probable | Oyster Intentional |
Regional Impacts
| Economic Impact | Fisheries | |
| Magallana gigas (Pacific Oyster) was introduced after the decline of M. angulata (Potuguese Oyster) due to disease. It is intensively reared along the Atlantic coast of France (Grizel and Hèral 1993; Goulletquer et al. 2002). | ||
| Ecological Impact | Parasite/Predator Vector | |
| Parasite-Predator vector- The introduction of M. gigas has been a possible/probable vector for a number of oyster foulers or predators in Atlantic French waters, including the seaweed Sargassum muticum, many other macroalgal species, Pteropurpura (=Ocinebrellus) inornata, Japanese Oyster Drill, the parasitic copepod Mytilicola orientalis, and the tunicates Botrylloides violaceus, Didemnum vexillum and Perophora japonica (Eno et al. 1999; Goulletquer et al. 2002). | ||
| Ecological Impact | Habitat Change | |
| The formation of extensive M. gigas reefs has created a new habitat on the rocky coasts and mud habitats of Brittany. Reef formation on mud bottoms resulted in a shift from suspension feeders to carnivores among the fauna. Reefs on rock led to an increase in deposit feeders (LeJart and Hily 2011; Herbert et al. 2016). In the Bay of Mont-St.-Michel, colonization by M. gigas has damaged polychaete reefs of Sabellaria laveolata (Cognie et al. 2006; Dubois et al. 2006; Desroy et al. 2011, all cited by Herbert et al. 2011). While invasion of mudflat and mussel bed habitats altered the density and diversity of epifauna, benthic assemlages were similar between M. gigas and native Ostrea edulis communities in Brittany (Zwerschke et al. 2016; Zwerschke et al. 2018). | ||