Invasion
Invasion Description
1st Record: CA/Bodega Harbor (1993, Introduced, Established, Grosholz and Ruiz 1995); Sonoma County/CA/Estero Americano (1989, one specimen, unknown establishment, Grosholz and Ruiz 1995)
Geographic Extent
Sonoma County/CA/Estero Americano (1989, one specimen, unknown establishment, Grosholz and Ruiz 1995); CA/Bodega Harbor (1993, Introduced, Established, Grosholz and Ruiz 1995)
Vectors
| Level | Vector |
|---|---|
| Alternate | Natural Dispersal |
| Alternate | Discarded Bait |
Regional Impacts
| Ecological Impact | Predation | |
| In Bodega Harbor CA, abundances of the clams Nutricola tantilla and N. confusa and the native crab Hemigrapsus oregonensis were sharply reduced after the invasion of Carcinus maenas. Experiments indicated high rates of feeding on the native clams and crabs (Grosholz et al. 2000). Over an 11-year period in Bodega Harbor, H. oregonensis abundance was negatively correlated with C. maenas abundance, but recovered, with a lag period, when C. maenas declined. However, C. maenas predation had persisting effects on the size and intertidal distribution of H. oregonensis (de Rivera et al. 2011). | ||
| Ecological Impact | Competition | |
| In laboratory experiments, Carcinus maenas spent more time at bivalve baits than the native crab Hemigrapsus oregonensis, and was more successful at approaching competitors surrounding bait than H. oregonensis, in Bodega Harbor California (Jensen et al. 2002). Carcinus maenas also displaces Metacarcinus magister (Dungeness Crabs) of equal size in feeding trials, and causes M. magister to emigrate from shelters in laboratory trials (McDonald et al. 2001). In enclosure experiments, Green Crabs reduced the abundance and quality of food available for wintering shorebirds (Dunlin, Calidris alpina) (Estelle and Grosholz 2012). | ||
| Ecological Impact | Trophic Cascade | |
| After the Carcinus maenas invasion in Bodega Bay Harbor, California, several invertebrate species, specifically the polychaetes Exogene sp. and Lumbrinereis sp. and the tanaid Leptochelia dubia increased in abundance, probably as an indirect effect of reduction in Nutricola spp. populations (Grosholz et al. 2000). The introduced clam Gemma gemma increased dramatically (two orders of magnitude) after the Carcinus invasion, apparently because of decreased competition from native Nutricola clams (Grosholz 2005). | ||
| Economic Impact | Fisheries | |
| In Bodega Bay, California, Manila Clams (Venerupis philippinarum) planted in mesh bags, were prone to heavy predation by Carcinus maenas. Predation was reduced by planting the clams later in the season, when the clams were larger (Grosholz et al. 2000). | ||