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Recent Observations on Colonization

Account of the appearance of Didemnum vexillum in New Zealand in 2001 and 2002

This report includes information on the infestation of the Steel Mariner barge by D. vexillum; images of the species; location maps; a report by P. Mather (Kott) on the identification of the didemnid; a survey of the didemnid on the barge and its spread to the seabed beneath it; and the potential risks posed by the spread of the species.

Coutts, A.D.M., 2002, A biosecurity investigation of a barge in the Marlborough Sounds (New Zealand): Cawthron Institute Report 744, 68 p. (PDF format)

Account of the appearance of Didemnum vexillum in Holyhead Harbour, North Wales, 2008  

This report includes information on:  the infestation of the Holyhead Marina by D. vexillum; results of a survey of the marina, the wider harbour, and other sites along the coast of Wales; images of the species, including brooding unhatched larvae; and location maps.

Holt, R., Ramsay, K., Mowat, S., Kent, F., and Griffith, K., 2009, Survey of non-native ascidian (sea squirt) Didemnum vexillum in Holyhead Harbour:  Countryside Council for Wales Marine Monitoring Report No. 67, 24 p. (PDF format)

Account of the appearance of the non-indigenous tunicates Didemnum vexillum, Styela clava, Ascidiella aspersa, and Diplosoma listerianum; and the non-indigenous anemone Diadumene lineata, in Nova Scotia Canada

Moore, A.M., Vercaemer, B., DiBacco, C., Sephton, D., and Ma, K.C.K, 2014, Invading Nova Scotia: first records of Didemnum vexillum Kott, 2002 and four more non-indigenous invertebrates in 2012 and 2013: Bioinvasions Records, volume 3, issue 4, p. 225-234. (PDF format)

Account of the presence of the non-indigenous tunicate Didemnum vexillum in the Bay of Fundy and its absence on offshore banks in eastern Canada.

Vercaemer, B., Sephton, D., Clement, P., Harman, A., Stewart-Clark, S., and DiBacco, C., 2015, Distribution of the non-indigenous colonial ascidian Didemnum vexillum (Kott, 2002) in the Bay of Fundy and on offshore banks, eastern Canada: Management of Biological Invasions, volume 6, issue 4, p. 385-394. doi: (PDF format)

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