Over the past decade, four exotic tunicates (Styela clava, Ciona intestinalis, Botrylloides violaceus and Botryllus schlosseri) have been reported in the Brudenell estuary in Prince Edward Island (PEI), Canada. Styela clava was the first exotic tunicate to arrive in 1997, rapidly establishing, spreading, invading, and eventually becoming a nuisance in several estuaries of PEI. In the Brudenell estuary, S. clava remained the only exotic nuisance tunicate until 2003. In the fall of 2004, the vase tunicate C. intestinalis, was reported in low abundance, followed by the two colonial species, B. schlosseri and B. violaceus, reported in the spring of 2005. The abundance of C. intestinalis rapidly increased post-introduction, eventually replacing S. clava as the foremost nuisance species on mussel farms in the estuary. To date, C. intestinalis continues to colonize this estuary at epidemic proportions, resulting in the continuing drop of S. clava abundance. The current abundance of C. intestinalis is estimated at 5 cm -2 , which is similar to S. clava abundance at its height in 2003. The 2006 abundance of S. clava is estimated to have fallen to near 0 cm -2 . The dominance of C. intestinalis as a fouling organism on mussel farms is considered a serious threat to this aquaculture industry, mainly due to its unmanageable weight. The process of the detection, establishment, invasiveness, and eventual rise to nuisance level of exotic tunicates in the Brudenell River is presented.

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Background: Late in the 1990s, the non-indigenous European green crab (Carcinus maenas) colonized the shorelines of eastern Prince Edward Island, in Atlantic Canada. Due to concerns of further spread into productive shellfish habitats, an annual survey was conducted between 2000 and 2013 to detect a potential range expansion of this species. We compiled and analyzed that data and document green crab expansion using records of annual occurrence and relative density. Methods: Surveys were conducted during the fall season of each year by deploying baited traps at 29 sites along the island's two main shorelines (north and south shores). These sites were selected based on areas deemed more likely to be invaded by the green crab. Raw data per site and date was transformed to catch per unit effort (CPUE) to estimate relative abundances. Results: Populations of this species showed an uneven westward expansion along the north and south shores. Expansion rates changed among years but, overall, crab abundance was higher and changes in abundance were faster along the south shore than the north shore of the island. The westward expansion continues until this day. Conclusions: Based on the information compiled we hypothesize that the dissimilarity in range expansion rate was related to the availability of suitable habitat to sustain large green crab populations along the south shore. We also discuss implications of this expansion for commercial shellfish and native coastal communities.

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