Invasion
Invasion Description
1st Record: Brest/(Brittany) France/Atlantic Ocean (1949, Blanchard 1997; Goulletquer et al. 2002)
Geographic Extent
France/Mont St. Michel Bay (1970s, Blanchard 2009); Kostecki et al. 2011); France/Bay of Morlaix (Riquet et al. 2016); Saint-Brieuc (Britanny)/ Gulf of St. Malo (Vallet et al. 2011); Brest/(Brittany) France/Atlantic Ocean (1949, Blanchard 1997; Goulletquer et al. 2002; 2010, 2013, Bishop et al. 2015b); France/Bay of of Morlaix (before 1960, Rigal et al. 2010); France/Bay of Borgneuf, Bay of Biscay (Le Pape et al. 2004); France/Pertuis Breton, Bay of Biscay (Le Pape et al. 2004); France/Pertuis d'Antioche, Bay of Biscay (Le Pape et al. 2004); Marennes-Oleron, Charentes-Maritime/France/Bay of Biscay (1969, Deslous-Paoli 1986: Betrand 2018; continuously distributed in Brittany/Fance/Atlantic Ocean-Bay of Biscay (Stiger-Pouvreau and Thouzeau 2015); Les Écréhous, Channel Islands/English Channel (1975, Department of the Environment, States of Jersey, now abundant throughout the islands)
Vectors
| Level | Vector |
|---|---|
| Alternate | Oyster Accidental |
| Alternate | Ballast Water |
| Alternate | Hull Fouling |
Regional Impacts
| Ecological Impact | Habitat Change | |
| Dense populations in Mont Saint-Michel Bay, Normandy, have created extensive shell beds, covering more than 25 km-2, and depositing 771 metric tons h-1 of organic matter into the sediment. The accumulation of organic matter makes sediment anoxic and the community becomes a shell reef, dominated by C. fornicata, other filter-feeders, and their predators living on or in the empty shells, but fewer burrowers (Blanchard 2009). Effects on benthic diversity and abundance, due to increased hard substrate on muddy bottoms, were noted in the Bay of Saint-Brieuc (increased diversity, but lower total abundance, Vallet et al. 2001) and in the Bay of Marennes-Oleron (higher diversity with higher overall abundance, de Montaudouin and Sauriau 1999). In the Bay of Brest, dense beds of C. fornicata shells were colonized by the native brittlestars Ophiocomina nigra and Ophiothrix fragilis. The spreading populations of brittlestars have probably contributed to mortality of C. fornicata (Blanchet-Aurigny et al. 2012). In three bays (Borgneuf, Pertuis Breton, Pertuis d'Antioche), the abundance of juvenile Common Sole (Solea solea) was negatively correlated with the abundance of C. fornicata (Le Pape et al. 2004). | ||
| Ecological Impact | Competition | |
| Crepidula fornicata and Crassostrea gigas (Pacific Oyster), in the Bay of Borgneuf, France, had substantial overlap in types of phytoplankton ingested in winter and early spring, but not in late spring and summer. The Slippersnail is more of an indiscriminate feeder, while the oyster is more selective (Decottignies et al. 2007a; Decottignies et al. 2007b). Lefebvre et al. (2009) suggest that the seasonal and system dynamics of estuaries may influence the appearance of competition among these species. In a more oceanic, well-mixed estuary, the food sources (phytoplankton) used by C. fornicata and C. gigas overlapped, but in a more estuarine bay, C. fornicata consumed more benthic microalgae. In laboratory experiments, Crepidula fornicata larvae fed at higher rates, and ate wider size range of phytoplankton than larvae of the oyster Crassostrea gigas. In Mont St. Michel Bay, larvae of C. fornicata can potentially deplete food resources for larvae of C. gigas (Blanchard et al. 2008). Crepidula fornicata competes for space with the King Scallop Pecten maximus in the Bay of Brest, Brittany, both for space on the bottom, and by attaching to the shells of the scallops (Frésard and Boncoeur 2006). | ||
| Economic Impact | Fisheries | |
| Crepidula fornicata adversely affects the fishery of the King Scallop Pecten maximus in the Bay of Brest, Brittany, both by competing for space on the bottom, and by attaching to the shells of the scallops, reducing the harvest, and requiring time and effort to scrape the scallops clean. Frésard and Boncoeur (2006) model the the costs and benefits of possible programs to reduce the abundance of the slipper limpets (eradication was considered impossible) and restocking scallops. | ||
| Ecological Impact | Herbivory | |
| Crepidula fornicata has developed dense populations in bays of Atlantic France, which have the potential to reduce phytoplankton concentrations (Blanchard 1997; Decottignies et al. 2007a; Decottignies et al. 2007b). In the Bay of Brest, France, a decrease in the magnitude of the spring phytoplankton bloom from 1979 to 1976, has been attributed to grazing by C. fornicata, which has doubled in abundance over that time span. Average chlorophyll concentrations have not been affected, probably due to increased nitrogen inputs and a shift in the phytoplankton community from diatoms to flagellates (Chavaud et al. 2000). | ||