Invasive Non-native Species

Coastal marine ecosystems

Photo: colonial sea squirts © Gordon KingAlthough many non-native species have become established in Canada’s coastal marine waters,4-6 the impacts of invasive non-native species are most acute in the bays of P.E.I. Intensive agriculture and aquaculture activities have made P.E.I.’s coast more susceptible to the establishment and impacts of invaders. For example, since 1997, four species of sea squirts, or tunicates, have established, and are invasive, in P.E.I. Although established elsewhere in the southern Gulf of St. Lawrence, they are only invasive in P.E.I. There is also some evidence that another invasive species, the European green crab, preys on the predators of sea squirts, exacerbating the problem in P.E.I.6, 7

The European green crab is an aggressive competitor of native crabs and a predator of clams, mussels, juvenile fish, and many other species. It has recently become established on both the east and west coasts of Canada, although its establishment is too recent for its full impact to be known. The main source of coastal marine invasions in Canada has been transport on the hulls and in the ballast water of ships.5, 7, 8 New regulations on ballast water are designed to prevent further introductions through this pathway.