Invasion
Invasion Description
1st record: Provincetown/MA/Cape Cod Bay (1872, Glude 1955; Almaca 1963)
Geographic Extent
Provincetown/MA/Cape Cod Bay (1872, Glude 1955; Almaca 1963); Sandwich/MA/Cape Cod Bay (2000, MIT Sea Grant 2003; O'Connor 2013); Barnstable/MA/Cape Cod Bay (MIT Sea Grant 2003); Manomet Point/MA/Cape Cod Bay (1902, Bryant 1906); Duxbury/MA/Plymouth Harbor (2002, MIT Sea Grant 2003); Marshfield/MA/Cape Cod Bay (O'Connor 2013); Cohassett/MA/Massachusetts Bay (1893, Bryant 1906); Scituate/MA/Massachusetts Bay (O'Connor 2013); Bay Pointe Marina, Quincy/MA/Massachusetts Bay (2000, MIT Sea Grant 2003); Constitution Marina, Boston/MA/Massachusetts Bay (2000, Introduced, Established, MIT Sea Grant 2003); Nahant/MA/Massachusetts Bay (1902, Bryant 1906); Lynn/MA/Massachusetts Bay (1902, Bryant 1906); Salem/MA/Massachusetts Bay (2003, Introduced, Established, MIT Sea Grant 2003); Tucks Point Marina, Beverly/MA/Massachusetts Bay (2000, MIT Sea Grant 2003); Annisquam, Gloucester/MA/Gulf of Maine (1884, MCZ 62262 Museum of Comparative Zoology 2009); Gloucester/MA/Annisquam River (Massachusetts Bay) (1935, Dexter 1947); Ipswich/MA/Gulf of Maine (1902, Bryant 1906); Hampton State Pier, Hampton/NH/Gulf of Maine (2003, MIT Sea grant 2003); UNH Coastal Marine Lab/Coast Guard Pier, Newcastle/NH/Great Bay (2003, MIT Sea Grant 2003); Kittery/ME/Gulf of Maine (1902, Bryant 1906); York/ME/York Harbor (2009, MIT Sea Grant 2009); Wells/ME/Wells Harbor (2007, MIT Sea Grant 2007); Kennebunk Beach/ME/Gulf of Maine (7-15-2009, MIT Sea Grant); Cape Elizabeth/ME/Dyers Cove, Casco Bay (2010, Massachusetts Office of Coastal Zone Management 2013);; Portland/ME/Casco Bay (1902, Introduced, Established, Bryant 1906); Harpswell/ME/Casco Bay (1905, Introduced, Established, Bryant 1906; Rathbun 1930); Brewer South Freeport Maine/ME/Casco Bay (2003, MIT Sea Grant 2003); Boothbay Harbor/ME/Boothbay Harbor (1907, Glude 1955); Friendship/ME/Gulf of Maine (1912, Glude 1955); Tenants Harbor/Maine/Gulf of Maine (1907, Glude 1955); Brooklin/ME/Blue Hill Bay (1930, Glude 1955); Bass Harbor/ME/Gulf of Maine (1937, Introduced, Established, Glude 1955); Winter Harbor/ME/Gulf of Maine (1939, Glude 1955); Mount Deser tIsland/ME/Atlantic Ocean (Williams et al. 2015, 43.86, 64.82, southern and northern (Scandinavian haplotypes)); ME/Cobscook Bay; Great Bar, Jonesport/ME/Gulf of Maine (1950, Glude 1955); Lubec/ME/Passamaquoddy Bay (1951, Glude 1955); St. Andrews/New Brunswick/Passamaquoddy Bay (1951, Introduced, Established, Glude 1955); Nova Scotia/Minas Basin (1953, Introduced, Established, Glude 1955; Audet et al. 2003); Sandy Cove/Nova Scotia/Bay of Fundy (1953, Audet et al. 2003); Cape Forchu/Nova Scotia/Gulf of Maine (1956, Audet et al. 2003); Nova Scotia/Chignecto Bay, Bay of Fundy (2012, MacDonald et al. 2018); Yarmouth/Nova Scotia/Gulf of Maine (2008, Choi et al. 2016)
Vectors
| Level | Vector |
|---|---|
| Alternate | Natural Dispersal |
| Alternate | Dry Ballast |
| Alternate | Hull Fouling |
Regional Impacts
| Ecological Impact | Predation | |
| Carcinus maenas preys on native invertebrate communities in the Gulf of Maine. Its prey in this region include the barnacle Semibalanus balanoides, the native periwinkle Littorina obtusata, Nucella lapillus (Dogwhelk) (Rangely and Thomas 1987), egg capsules of Nassarius obsoletus, and probably those of other snails, as well as Mya arenaria (Soft-Shelled Clam) (Dow and Wallace 1952; Glude 1955; Brenchley 1982; Rangely and Thomas 1987). In the tidal Damariscotta River estuary, and the exposed Pemaquid Point, predation by C. maenas limited recruitment of Blue Mussels (Mytilus edulis), in areas with slow current flow (Bertness et al. 2002; Bertness et al. 2004). Since the arrival of C. maenas, populations of the poorly dispersing N. lapillus and L. obtusata have developed thicker shells, increasing resistance to predation (Vermeij 1982a; Seeley 1986). [However, overall shell length of N. lapillus also increased sufficiently to account for increased shell thickness, suggesting that factors other than predation- including, temperature, wave action, etc, may have influenced this trend (Fisher et al. 2009).] Evidence for the impacts of C. maenas include observed declines in clam populations after its arrival (Glude 1955), gut contents examination, and laboratory experiments (Rangeley and Thomas 1987). Shells of Littorina obtusata (Smooth Periwinkle) from the northern and southern Gulf of Maine show differences in shell thickness related to Carcinus maenas abundance and the length of exposure to the invader (~100+ years for southern Gulf, ~50 years for northern Gulf). These differences are indicative of natural selection by Carcinus predation. These temporal and geographical differences have not been found in Littorina littorea, possibly because of the long-range dispersal of its planktonic larvae (Vermeij 1982b). In L. obtusata, shell thickness is increased after the snail is exposed to odors of C. maenas and is larger when accompanied by the odor of crushed L. obtusata (Trussell and Nicklin 2002). This response is greater in southern Gulf populations than those from Quoddy Bay (Trussell and Nicklin 2002). A similar difference in antiipredator responses to C. maenas between northern and southern Maine populations was seen in the Dogwinkle Nucella lapillus (Large and Smee 2013). In a system of tidepools at Nahant, Littorina littorea (Common Periwinkle) responded to increased C. maenas density by moving to other pools (Trussell et al. 2004). Interactions among crabs of different sizes often result in predation, either among crabs of the same species or different species. Large C. maenas prey on small Hemigrapsus sanguineus and vice versa (Griffen and Byers 2009). Predation, aggression, and interference behavior have the effect of reducing the predation rates of both species when the co-occur. Experiments and modeling indicate that predation by Carcinus maenas and Hemigrapsus sanguineus is likely to reduce the use of intertidal habitats by the native Cancer irroratus (Rock Crab) in the Gulf of Maine (Griffen and Riley 2015). In laboratory experiments, Carcinus maenas was found to consume juvenile lobsters in 6 of 11 trials (Rossong et al. 2006). However, field and laboratory experiments (in Passamquoddy Bay, New Brunswick and the Isles of Shoals, Maine) indicate that rates of predation are low, and that predation on Green Crabs by lobsters may be equally or more frequent (League-Pike and Shulman 2009; Lynch and Rochette 2009). Predation by Carcinus maenas has affected the behavior and morphology of Softshell Clams (Mya arenaria) in the Gulf of Maine. In the Wells estuary, clams burrow deeper in the presence of crabs. This is triggered by chemical clues, which also induce growth of longer siphons (Whitlow et al. 2003; Whitlow 2010). High densities of Green Crabs were reported by shellfishers in Casco Bay, coinciding with higher water temperatures in 2013. This population growth was associated with an absence of young Softshell Clams (Mya arenaria) (Neckles 2015). | ||
| Economic Impact | Fisheries | |
| Carcinus maenas preys on commercial shellfish in the Gulf of Maine. Its primary prey there has been Mya arenaria (Soft-Shell Clam). Decreased landings and rapid mortality of newly planted clams has been observed as C. maenas invaded new localities in the Gulf of Maine (Dow and Wallace 1952; Glude 1955; Smith et al. 1955). Tan and Beal (2015) tested various types of netting used to exclude Green Crabs, and found that significant predation occurred, even when small clams were protected by netting, Crab predation can be underestimated, because some clams are consumed without damage to the shells (Tan and Beal 2015). Carcinus maenas does have minor commercial value as a bait animal. | ||
| Ecological Impact | Trophic Cascade | |
| In a system of tidepools at Nahant, Massachusetts, Littorina littorea (Common Periwinkle) responded to increased C. maenas density by moving to other pools. The reduction of grazing resulted in increased growth of ephemeral red and green algae (Trussell et al. 2004). Although it had a direct predatory effect on mussls and barnacles in community experiments, Carcinus maenas had an indirect positive effect by preying on the dogwhelk Nucella lapillus (Griffen and Byers 2009). In laboratory experiments, C. maenas preyed intensely on the sea slug Placida dendritica, which grazes on Codium fragile, which could favor the growth of the seaweed in favorable habitats for C. maenas, such as enclosed harbors and estuaries (Harris and Jones 2005). Caging experiments show that compettion by Carcinus maenas reduces abudances of the Marsh Crab (Sesarma reticulum) by evicting the smaller crabs from their burrows, and exposing the Marsh Crabs to predation. The reduction in Marsh Crab hebivory has resulted in increased growth and recovery of Spartina alterniflora saltmarshes. The previous decline of the Spartina marshes has been attrributed to an increase in the herbivorous Marsh Crab, triggered by heavy fishing fot predatory fishes (Coverdale et al. 2013). | ||
| Ecological Impact | Competition | |
| Interference competition and aggression occur between Carcinus maenas and Hemigrapsus sanguineus. In experiments, interference between the two species lowered the predation rates of both species on amphipods (Griffen and Byers 2006). In laboratory experiments, Carcinus maenas was found to compete with juvenile lobsters for food and shelter (Rossong et al. 2006). However, in field studies in Passamaquoddy Bay, the two species did not seem to interact (Lynch and Rochette 2009). In Lynch and Rochette's experiments, agonistic behavior was rare. Carcinus maenas did compete with the native Dogwhelks (Nucella lapillus in Passamaquoddy Bay, interfering with whelks feeding on mussels (Mytilus edulis), and stealing prey from them. This kleptoparasitism may enable crabs to feed on mussels larger than they can open by themselves (Quinn et al. 2012). | ||
| Ecological Impact | Food/Prey | |
| Field and laboratory experiments in Passamquoddy Bay, New Brunswick and the Isles of Shoals, Maine indicate that Green Crab are frequent prey for American Lobsters (Homarus americanus) and their vulnerability to predation limits C. maenas subtidal distribution (League-Pike and Shulman 2009; Lynch and Rochette 2009). | ||
| Ecological Impact | Habitat Change | |
| High densities of Green Crabs were reported by shellfishers in Casco Bay, coinciding with higher water temperatures in 2013. The population explosion was associated with a sharp reduction of Eelgrass (Zostera marina) in upper Casco Bay, due to damage to the plants during foraging. Exclosure experiments found that survival of eelgrass shoots was 82% inside the exclosures, but 24% outside (Neckles 2015). | ||