Repeated rapid assessment surveys reveal contrasting trends in occupancy of marinas by non-indigenous species on opposite sides of the western English Channel.

Rapid assessment surveys of non-indigenous species (NIS) of sessile invertebrates were made at seven marinas in NW France and 10 marinas in SW England in 2010, and repeated in 2013. Fourteen NIS were recorded, 12 of which were seen on both coasts. Site occupancy differed between the opposite sides of the western English Channel. In Brittany, most species occurred at most sites in both 2010 and 2013. In 2010, site occupancy in Devon & Cornwall was distinctly lower; by 2013, the difference compared to Brittany had narrowed considerably, largely because of rapid colonisation of additional sites by species that were infrequent in 2010. Three more of the recent NIS are present in Devon & Cornwall but have still not become widespread. It is concluded that the recently introduced fouling animals studied here are longer established in NW France than in SW England, and have probably spread northwards across the Channel.

[1]  L. C. Rao,et al.  Rapid Assessment Survey for Exotic Organisms in Southern California Bays and Harbors, and Abundance in Port and Non-port Areas , 2005, Biological Invasions.

[2]  J. Ryland,et al.  First occurrence of the non-native bryozoan Schizoporella japonica Ortmann (1890) in Western Europe. , 2014, Zootaxa.

[3]  Robin A. Clark,et al.  Non-native Marine Species in British Waters: A Review and Directory , 1997 .

[4]  K. Reise,et al.  Oyster Imports as a Vector for the Introduction of Alien Species into Northern and Western European Coastal Waters , 2002 .

[5]  P. Dyrynda,et al.  The distribution, origins and taxonomy of Tricellaria inopinata d'Hondt and Occhipinti Ambrogi, 1985, an invasive bryozoan new to the Atlantic , 2000 .

[6]  Brendan Gould,et al.  Survey evaluations to assess marine bioinvasions. , 2007, Marine pollution bulletin.

[7]  J. Ryland,et al.  Alien species of Bugula (Bryozoa) along the Atlantic coasts of Europe , 2011 .

[8]  G. Lambert.  The south temperate and Antarctic ascidian Corella eumyota reported in two harbours in north-western France , 2004, Journal of the Marine Biological Association of the United Kingdom.

[9]  M. Héral,et al.  Introduction into France of the Japanese oyster ( Crassostrea gigas ) , 1991 .

[10]  Elizabeth Cook,et al.  Changing coasts: marine aliens and artificial structures , 2012 .

[11]  C. Monniot,et al.  Apparition de l'ascidie Perophora japonica sur les côtes et dans les ports de la Manche , 1985 .

[12]  Dan Minchin,et al.  Rapid coastal survey for targeted alien species associated with floating pontoons in Ireland , 2007 .

[13]  Joshua A. Mackie,et al.  Recent discoveries of alien Watersipora (Bryozoa) in Western Europe, with redescriptions of species , 2009 .

[14]  T. Therriault,et al.  Recreational boating: a large unregulated vector transporting marine invasive species , 2011 .

[15]  R. Thresher,et al.  Man-made marinas as sheltered islands for alien marine organisms: Establishment and eradication of an alien invasive marine species , 2002 .

[16]  F. Viard,et al.  The Southern Hemisphere ascidian Asterocarpa humilis is unrecognised but widely established in NW France and Great Britain , 2013, Biological Invasions.

[17]  T. Nishikawa,et al.  Occurrence of the alien ascidian Perophora japonica at Plymouth , 2000, Journal of the Marine Biological Association of the United Kingdom.

[18]  G. Lambert.  Adventures of a sea squirt sleuth: unraveling the identity of Didemnum vexillum, a global ascidian invader , 2009 .

[19]  M. Burrows,et al.  Distribution of the invasive bryozoan Tricellaria inopinata in Scotland and a review of its European expansion. , 2013 .

[20]  E. Cook,et al.  Rapid assessment of the distribution of marine non-native species in marinas in Scotland , 2006 .

[21]  S. Galatowitsch.  Invasive aquatic species of Europe , 2004 .

[22]  M. Bishop.  Establishment of an Immigrant Barnacle in British Coastal Waters , 1947, Nature.

[23]  Judith Pederson,et al.  Alien species and other notable records from a rapid assessment survey of marinas on the south coast of England , 2006, Journal of the Marine Biological Association of the United Kingdom.

[24]  M. Verlaque,et al.  Biological Invasion: The Thau Lagoon, a Japanese Biological Island in the Mediterranean Sea , 2010 .

[25]  M. Verlaque.  Checklist of the macroalgae of Thau Lagoon (Hérault, France), a hot spot of marine species introduction in Europe , 2001 .

[26]  D. B. Carlisle.  Styela mammiculata n.sp., a new species of ascidian from the Plymouth area , 1954, Journal of the Marine Biological Association of the United Kingdom.

[27]  S. Jenkins,et al.  First records in Great Britain of the invasive colonial ascidian Didemnum vexillum Kott, 2002 , 2009 .

[28]  M. Blanchard.  Origine et état de la population de Crepidula fornicata (Gastropoda Prosobranchia) sur le littoral français , 1995 .

[29]  K. Reise,et al.  Nonnative macrobenthos in the Wadden Sea ecosystem , 2012 .

[30]  O. De Clerck,et al.  Polyopes lancifolius (Halymeniales, Rhodophyta), a new component of the Japanese marine flora introduced to Europe , 2010 .