Invasion
Invasion Description
1st record: Margaree Harbor and Pleasant Bay/Nova Scotia/Gulf of St. Lawrence (1994, Audet et al. 2003); Antigonish/Nova Scotia/Georges Bay (1997, Audet et al. 2003); Reports of Carcinus maenas occurring in Northumberland Strait in 1960 are erroneous (Audet et al. 2003)
Geographic Extent
Rocky Harbour/Newfoundland/Bonne Bay (2010, Fisheries and Oceans Canada 2011); Stephensville/Newfoundland/St. Georges Bay (2008, Fisheries and Oceans Canada 2011); Maragaree Harbor and Pleasant Bay/Nova Scotia/Gulf of St. Lawrence (1994, Audet et al. 2003); Antigonish/Nova Scotia/Georges Bay (1997, Audet et al. 2003); Merigomish/Nova Scotia/Northumberland Strait (1998, Audet et al. 2003); Wallace Bay/Nova Scotia/Northumberland Strait (2001, Audet et al. 2003); Port Elgin/New Brunswick/Baie Vert (Northumberland Strait) (2002 , Audet et al. 2003); Murray Harbour/Prince Edward Island/Gulf of St. Lawrence (1998, Audet et al. 2003); Cardigan/Prince Edward Island/Gulf of St. Lawrence (1997, Audet et al. 2003); Savage Harbour/Prince Edward Island/Gulf of St. Lawrence (2001, Audet et al. 2003); Charlottetown/Prince Edward Island/Northumberland Strait (2000, Audet et al. 2003); Madeleine Islands/Quebec/Grand Entree lagoon (Simard et al. 2005); Chandler & Grande-Rivière, Gaspe Peninsula/Quebec/Gulf of St. Lawrence (8/2011, Foster in ICES Advisory Committee on the Marine Environment 2012, 14 juveniles); St. Pierre and Miquelon/France/Gulf of St. Lawrence (2017, ICES WGITMO 2018, 2 inidividuals_
Vectors
| Level | Vector |
|---|---|
| Alternate | Natural Dispersal |
| Alternate | Hull Fouling |
| Alternate | Fisheries Accidental (not Oyster) |
| Alternate | Ballast Water |
Regional Impacts
| Economic Impact | Fisheries | |
| In cage experiments on a mudflat in Pomquet Harbour, Nova Scotia, Carcinus maenas removed 80% of small Softshell Clams (Mya arenaria), but had negligable impacts on larger clams (Floyd and Williams 2004). In experimental trials on Prince Edward Island, Green Crabs preyed on juvenile quahogs (Mercenaria mercenaria), blue mussels (Mytilus edulis), soft-shell clams (Mya arenaria), and oysters (Crassostrea virginica), and preferred mussels and clams in choice experiments (Miron et al. 2005). In predation experiments, large and medium C. maenas caused high mortality among small (35-55 mm long) Eastern Oysters, posing a problem for oyster aquaculature (Pickering et al. 2017; Poirier et al. 2017). The possibility of a managed fishery, on Prince Edward Island, has been studied, but its success would be determined by market prices (St. Hilaire et al. 2016). Large numbers of Green Crabs and naitve Rock Crabs (Cancer irroratus) decrease the number of American lobsters entering lobster traps, but it is not related to invasion status ( | ||
| Ecological Impact | Predation | |
| In cage experiments on a mudflat in Pomquet Harbour, Nova Scotia, Carcinus maenas removed 80% of small Softshell Clams (Mya arenaria), but had negligable impacts on larger clams (Floyd and Williams 2004). In experimental trials on Prince Edward Island, Green Crabs preyed on juvenile quahogs (Mercenaria mercenaria), blue mussels (Mytilus edulis), soft-shell clams (Mya arenaria), and oysters (Crassostrea virginica), and preferred mussels and clams over oysters in choice experiments (Miron et al. 2005). Pickering and Quijon (2011) also found a similar pattern, with a strong preference for soft-shell clams (Mya arenaria) over mussels and oysters, particularly for small crabs (35-45 mm), which did not feed on large mussel and oysters at all, in choice experiments. Feeding rates of small, medium, and large C. maenas were highest on small bivalves, especially soft-shell clams (Pickering and Quijon 2011). In predation experiments, large and medium C. maenas caused high mortality among small (35-55 mm long) Eastern Oysters (Pickering et al. 2017; Poirier et al. 2017). | ||
| Ecological Impact | Habitat Change | |
| Severe declines in an Eelgrass (Zostera marina) bed in Antigonish Harbour, Gulf of St. Lawrence, Nova Scotia, were associated with foraging by abundant Green Crabs (Carcinus maenas uprooting and and damaging the plants. Enclosure experiments supported the role of the crabs in the damage to Eelgrass beds (Garbary et al. 2014). | ||
| Ecological Impact | Food/Prey | |
| American Lobsters (Homarus americanus) in lobster traps prey on both Green Crabs and Rock Crabs (Cancer irroratus) (Zargarpour et al. 2020). | ||
| Ecological Impact | Herbivory | |
Green Crabs (Carcinus maenas) were implicated in a decline of a protected population of Chondrus crispus (Irish Moss). Removal programs were undertaken in two Prince Edward Island harbors, Murray Bay and Basin Head. Populations were reduced to 30-40& of the initial level, with short-term crab reductions, and Irish Moss recovery (Tummon Flynn et al. 2023). | ||
| Ecological Impact | Herbivory | |
Green Crabs (Carcinus maenas) were implicated in a decline of a protected population of Chondrus crispus (Irish Moss). Removal programs were undertaken in two Prince Edward Island harbors, Murray Bay and Basin Head. Populations were reduced to 30-40& of the initial level, with short-term crab reductions, and Irish Moss recovery (Tummon Flynn et al. 2023). | ||