Marine boating habits and the potential for spread of invasive species in the Gulf of St. Lawrence.

The potential for boating to disperse the clubbed tunicate Styela clava Herdman, 1881 and green crab Carcinus maenas (Linnaeus, 1758) in the southern Gulf of St. Lawrence was investigated using interviews with recreational and commercial boaters in eastern Prince Edward Island (PEI). Boaters were asked how long their boat had been at the present location; the primary use of the boat; if anchors, sounding equipment or fishing gear were used; whether any organisms were attached to these items when retrieved; and the fate of those organisms. Bilge water and hull scrapings from the vessels contained 31 and 47 taxa, respectively. Recreational boats, nearly half of which were docked outside their home estuary, were a more likely vector of dispersal than commercial fishing boats that tended to return to the same port each night. Northeastern Nova Scotia and the southern coast of PEI were most at risk for the spread of clubbed tunicate, while green crab could be transported to PEI and eastern New Brunswick. The Magdalen Islands, Quebec, were also predicted as a site to which green crabs could spread, and the first green crabs were detected there two years after our study.