Clavopsella navis
Date of introduction and origin
Clavopsella navis was first noted in 1973 (P.F.S.
Cornelius pers. comm.) in Widewater Lagoon, Shoreham, West
Sussex. Its origin is not known since it has only ever been found
in the vicinity of ports and harbours, presumably as an
introduction.
Method of introduction
It was probably transported on ships' hulls.
Reasons for success
Many hydroids are substrate generalists which probably assists
in their distribution on ships and other slow-moving material as
well as establishment upon arrival in foreign ports etc.
Rate of spread and methods involved
In Britain, C. navis is not known to have spread
outside the one lagoon where it is found.
Distribution
Widewater Lagoon, West Sussex, contains the only known British
population. Elsewhere in Europe it is known from the Kiel Canal,
Germany, and the Azores. Outside Europe, it is only known from Cape
Town harbour, South Africa (Barnes 1994). It is a brackish-water
species.
Factors likely to influence spread and distribution
Its spread is likely to be influenced by slow-moving shipping
entering brackish waters.
Effects on the environment
Unknown.
Effects on commercial interests
Unknown.
Control methods used and effectiveness
None used.
Beneficial effects
None known.
Comments
None.
References
Barnes, R.S.K. 1994. The brackish-water fauna of
northwestern Europe. Cambridge, Cambridge University
Press.
Millard, N.A.H. 1959. Hydrozoa from ships' hulls and
experimental plates in Cape Town docks. Annals of the South
African Museum, 45:239-256.
Millard, N.A.H. 1975. Monograph on the Hydroida of southern
Africa. Annals of the South African Museum, 68.
(pp.100-102)
Acknowledgements (contributions from questionnaire)
Dr P.F.S. Cornelius, The Natural History Museum, London.