The European green crab, Carcinus maenas, is one of the most widely distributed invasive species in coastal systems. This species has become established on five continents and has produced significant negative ecological and economic impacts in many areas. On the Atlantic coast of North America, green crabs have been established for at least 180 years. On the Pacific coast, green crabs became established in San Francisco Bay in the late 1980s and expanded their range rapidly during the 1990s. In response to the spread and impacts of green crabs in the U.S., Carcinus maenas was listed as an aquatic nuisance species by the federal Aquatic Nuisance Species Task Force (ANSTF). To date, there have been no formal review of the ecological impacts of green crabs and no formal attempts to quantify and understand their potential economic impacts. This paper presents a predictive framework for understanding the magnitude and extent of green crab impacts on the East and West Coasts of the U.S. The framework consists of several linked models. The ecological sub-models incorporate green crab dispersal and relationship between green crab abundance and the dynamics of prey populations. The economic analysis focuses on the green crab impacts on commercial shellfisheries and estuarine restoration efforts. The documented historical and present impacts of green crabs on the shellfishery include soft-shell clams, blue mussels, scallops, hard shell clam, and manila clams. The preliminary results of this analysis show that damages to commercial shellfishery from Green Crab predation are on average $22.6 million per year on the East Coast of the United States. Although the current damages on the West Coast are negligible, the potential future damages are likely to increase to $0.84 million per year, if Green Crab invades Puget Sound (WA) and Alaska.


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