Potential ecological implications from the introduction of the European green crab, Carcinus maenas (Linneaus), to British Columbia, Canada, and Washington, USA

Abstract

We evaluate the potential impact of the European green crab Carcinus maenas (Linneaus) (Decapoda: Portunidae) on possible prey species in British Columbia, Canada, and Washington State, USA. This crab was first observed on the west coast of North America in San Francisco Bay, CA, in 1989. In early 1997, adult green crab were found in Coos Bay, Oregon, about 300 km further north than its previous known range limit (Humbolt Bay, CA). Ocean current transport of larvae may introduce it to Canada in the near future. The green crab is a versatile predator with a preference for molluscan and crustacean prey. In the Pacific, green crab seem to thrive best in habitats protected from oceanic swell, and the Strait of Georgia/Puget Sound are expected to provide ideal habitat, as are coastal estuaries in Washington State. These areas are main production areas for both intertidal bivalves and Dungeness crab (Cancer magister Dana) fisheries. It is expected that both bivalve and crab fisheries will be negatively impacted by the presence of green crab. Deltas in the Strait/Sound also support extensive migrating shorebird populations. Any change in densities of small invertebrates arising from green crab occurrence and predation may affect these migrating species, with ecological implications extending far beyond the actual potential range occurrence of green crab. We discuss the need for monitoring measures which will document the impact of this exotic species on local ecosystems when it ultimately extends its range to Canada.