Chinese mitten crabs (Eriocheir sinensis ) in the St. Lawrence River and Estuary, Canada: new records and risk of invasion

Recent reports of Chinese mitten crabs (Eriocheir sinensis) in the St. Lawrence River and Estuary were compiled to assess the possible sources of the species based on genetic analyses and data on shipping traffic. Between 2004 and 2007, nine specimens were captured in both the fresh and estuarine waters of the St. Lawrence; a number unprecedented in the 40 years since the mitten crab was first sighted in the Great Lakes–St. Lawrence Basin. These sightings, added to those of the eastern United States, are indicative of a large-scale wave of introduction of the mitten crab to Eastern North America. Genetic analyses have suggested that the St. Lawrence specimens likely originated in Europe. No significant changes have been noted in maritime traffic to the St. Lawrence in recent years, but analyses have revealed that 42% of ships came from European countries where established populations of Chinese mitten crab have exhibited recent bursts in abundance. It is suggested that the recent wave of introduction of mitten crabs to Eastern North America is related more to changes in the abundance of European populations than to changes in shipping vector activity. These recent sightings are of major concern with regard to the establishment and spread of the species. It is therefore recommended that long-term monitoring programs be set up immediately to track the progress of the mitten crab invasion in the St. Lawrence River basin.