Research Document - 2008/041

Risk Assessment for Chinese mitten crab (Eriocheir sinensis) in Canadian Waters

By T.W. Therriault, L.M. Herborg, A. Locke, and C.W. McKindsey

Abstract

Non-indigenous species continue to be dispersed to new environments and in recent decades the Chinese mitten crab (Eriocheir sinensis) continues to be introduced to new environments, including the east coast of North America. A risk assessment was undertaken In order to determine the potential risk posed by Chinese mitten crab to Canadian waters, including both the Atlantic and Pacific coasts (and adjacent inland waters). Most global introductions of mitten crabs either have been attributed to commercial shipping activities or intentional introductions (e.g., as a food source). Chinese mitten crab has been reported from several locations in eastern Canada but the extent of the invasion is not well known. Based on impacts of Chinese mitten crab elsewhere and non-indigenous species in general, there is considerable concern about the potential biological, habitat, and genetic impacts if this species becomes established and spreads in Canada. Life history characteristics of Chinese mitten crab could enhance long-distance natural dispersal and further dispersal via ballast water is probable, but a number of other potential vectors exist.

Fisheries and Oceans Canada conducted a national risk assessment to determine the potential risk posed by this non-indigenous crab in Canada. This assessment included evaluating the probability of arrival, survival, reproduction and spread and associated consequences as a measure of risk. In addition, the risk posed by potential pathogens, parasites or fellow travelers (e.g. other invasive species) was evaluated should Chinese mitten crab be introduced. These components were assessed in an expert peer-review workshop held in February 2008 using the best available information on biology, potential vectors of introduction, and impacts in both native and introduced ranges of Chinese mitten crab. The assessment concluded that Chinese mitten crab generally posed a moderate risk on both coasts although habitat impacts such as riverbank erosion were deemed higher risk. For pathogens, parasites or fellow travelers the risks also were moderate. However, as little is known about many potential pathogens, parasites and fellow travelers of this crab species, with the exception of a lung fluke that could infect humans, there was considerable uncertainty about potential hitchhiking organisms.

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