Acartia tonsa
Date of introduction and origin
Acartia tonsa was first recorded from Southampton
Water by between 1916 and 1956 Conover (1957). This copepod was
first reported in France by Remy (1927). It was previously known
from the western Atlantic and Indo-Pacific coasts although it is
not known from where it was introduced.
Method of introduction
It was possibly introduced through transport on ships hulls
and/or in ballast waters (Remy 1927).
Reasons for success
Tolerance of low salinities found in estuaries will have
contributed to its success.
Rate of spread and methods involved
Not known.
Distribution
In Britain this species has been found in Southampton Water
(Conover 1957), the Tamar estuary, Devon and Cornwall, the Exe
estuary in Devon (J.A. Lindley pers. comm.) and the Firth of Forth
(Taylor 1987). European populations occur from Normandy to the Gulf
of Finland (Brylinski 1981).
Factors likely to influence spread and distribution
Its distribution will be influenced by shipping as it occurs
in estuarine sites of less than 33%o salinity, which are also of
higher temperatures than off-shore waters and provide the
temperatures required for reproduction.
Effects on the environment
Unknown.
Effects on commercial interests
None.
Control methods used and effectiveness
None used.
Beneficial effects
None known.
Comments
This species produces diapause eggs (Zilhoux & Gonzalez
1972) which may have helped with transport in ballast waters.
References
Brylinski, J.M. 1981. Reports on the presence of Acartia
tonsa Dana (Copepoda) in the area of Dunkirk and its
geographical distribution in Europe. Journal of Plankton
Research, 3: 255-261.
Conover, R.J. 1957. Notes on the seasonal distribution of
zooplankton in Southampton Water with special reference to the
genus Acartia. Annals and Magazine of Natural
History, 12th Series, 10:
63-67.
Remy, P. 1927. Note sur un copépode de la saumâtre du canal de
Caen à la mer. Annales de Biologie Lacustre, 15:
169-186.
Rose, M. 1933. Copépodes pélagiques. Paris, Paul
Lechevalier. (Faune de France, No. 26.)
Taylor, C.J.L. 1987. The zooplankton of the Forth, Scotland.
In: The natural environment of the estuary and Firth of
Forth, ed. by D.S. McLusky.Proceedings of the Royal
Society of Edinburgh, 93B (3/4): 377-388.
Zilhoux, E.J., & Gonzalez, J.G. 1972. Egg dormancy in a
neritic calanoid copepod and its implications to overwintering in
boreal waters. In: 5th European Marine Biology
Symposium, ed. by B. Battaglia, 217 -230, B. Padova, Piccin
Editore.
Acknowledgements (contributions from questionnaire)
J.A. Lindley, Plymouth Marine Laboratory.