European Green Crab, Carcinus maenas

Investigations of the range of expansion of an invasive species: the European green crab, Carcinus maenas

Paul Jivoff, Greg Ruiz, Tuck Hines, Catherine DeRivera

Invasive species are increasingly common in marine and estuarine systems, and many invasions are having significant ecological and economic impacts. One of the most successful and destructive marine invaders is the European green crab, Carcinus maenas, designated recently by the Aquatic Nuisance Species Task Force as our nation's first marine nuisance species. A native of the Atlantic coast of Europe, it has successfully invaded both coasts of the United States.  As a predator on bivalves and other benthic invertebrates, it has altered the composition of benthic communities, and has been implicated in the decline of some shellfisheries. Once it invades, the green crab quickly establishes local populations and spreads rapidly on a regional scale. However, in eastern North America, green crab range expansion differs from that of other regions such that, the southern distribution appears more stable, and it does not extend to latitudes south of Chesapeake Bay (Figure 1). 

We are testing the relative roles of temperature and interactions with the blue crab, Callinectes sapidus, on local habitat use, mortality, and southward expansion of green crabs along eastern North America.  With field sampling from Chesapeake Bay to Maine and experiments in the field and laboratory, we are assessing if (1) a negative correlation exists between the abundance of green crabs and blue crabs, locally (Figure 2) and regionally (Figure 1); (2) blue crabs influence habitat use (Figure 3) and mortality of green crabs in the field; (3) experimental removal or additions of blue crabs in the field and laboratory, effect habitat use and mortality of green crabs; and (4) temperatures in Chesapeake Bay exceed those of other regions where green crabs occur. 

The results hope to identify the communities and habitats that are susceptible to invasion by green crabs, address species interactions and the potential distribution of invasions, and determine if biotic resistance alters the outcome of invasions among sites. The results also have implications for the role of fisheries management on invasion dynamics.  With blue crab populations at their lowest levels in 30 years and increasing fishing pressure, continued intense removal of blue crabs might render Chesapeake Bay and other estuaries currently beyond the green crab's range, more susceptible to invasion by green crabs.

These results were published in Ecology in 2005

de Rivera CE, Ruiz GM, Hines AH, Jivoff P. 2005. Biotic resistance to invasion: native predator limits abundance and distribution of an introduced crab. Ecology 86:3364-3376

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