Date of introduction and origin
Hydroides ezoensis was first recorded in 1976 in
Southampton Water and is thought to have been introduced in that
year (Thorp, Pyne & West 1987; Zibrowius & Thorp 1989)
probably from Japan. It originates in Asia where it is found on the
Japanese and east Chinese coasts, and the Russian coast of the Sea
Method of introduction
Probably introduced on the hulls of Nissan and Datsun car
transporters to Southampton, Hampshire, and possibly also in
ballast water (C.H. Thorp pers. comm.).
Reasons for success
Its success in Southampton Water was due to high levels of
phytoplankton and hot summers. This would have encouraged this
suspension-feeding serpulid to grow rapidly and reproduce. Success
is also possibly due to a lack of predators and favourable physical
conditions, including long residence time of water in the dock.
Southampton Water is dominated by phytoplankton populations which,
in summer, may exceed those elsewhere in the Solent by a factor of
three or four (Anon 1976; Williams 1980). 1976 witnessed an
extraordinarily prolonged and hot summer with sufficient sunshine
to maintain high levels of phytoplankton within Southampton Water.
High levels of phytoplankton, coupled with elevated temperatures
within Southampton Water, would have enabled this
suspension-feeding serpulid both to grow rapidly and to reproduce.
Crisp (1958) emphasised that Southampton Water, due to its enclosed
nature and small tidal range, would exchange water very slowly with
that of the Solent. The consequent 'retention' of water within
Southampton Water could have contributed to a rapid build-up of the
H. ezoensis population through retention of larvae, as
Crisp (1958) suggested for the non-native barnacle Elminius
Rate of spread and methods involved
This species has not spread outside the Solent (Thorp, Pyne
& West1987; Zibrowius & Thorp 1989). It was introduced into
France with Crassostrea gigas (Gruet, Héral & Robert
1976; Zibrowius 1978) but died out (Thorp, Pyne & West
It is only found in the Solent area, including the harbours
complex of Portsmouth, Langstone and Chichester. Outside of
Southampton Water numbers are very small and, apart from a
significant population at Cowes, Isle of Wight, comprise mostly
single individuals with no aggregation. A dense fouling population
on the hull of HMS Cavalier, transferred from Southampton
Water to Brighton Marina in 1984, failed to reproduce and rapidly
deteriorated (C.H. Thorp pers. comm.). The only other record in
Europe was from the Atlantic coast of France (Gruet, Héral &
Robert 1976; Zibrowius 1978) where Hydroides ezoensis was
introduced with imported oyster spat from Japan. This introduction
was very short-lived and apparently did not spread from the point
of introduction (Thorp, Pyne & West 1987).
Factors likely to influence spread and distribution
It only survives where there are good planktotrophic waters
and its failure to colonise Brighton Marina following transfer on a
ship's hull may be due to insufficient food availability (Thorp,
Pyne & West 1987). In its native Japanese waters
H.ezoensis appears to require temperatures of
approximately 20oC to spawn and settle (Miura & Kajihara 1984).
However, its distribution suggests that lethal temperatures have
little influence over the spread of the species. Thorp (1994) has
shown for the serpulid Ficopomatus enigmaticus that even
when minimum temperatures are reached, spawning may be delayed in
the absence of adequate phytoplankton (Himmelman 1980).
Effects on the environment
It has unknown effects, although perhaps some displacement of
'waterline' green algae Ulva and Enteromorpha
occurs (C.H. Thorp pers. comm.). It has not displaced the heavy
sea-squirt-dominated fouling community at an immediately lower
Effects on commercial interests
It is a severe fouling organism on harbour structures and
ships' hulls throughout Southampton Water. While this additional
fouling load does not appear to have had any deleterious effect on
fixed harbour structures, it has caused flotation problems of buoys
and added considerably to fouling of poorly-protected ships.
Control methods used and effectiveness
It can be removed by scraping of buoys and ships' hulls.
It probably adds to the diversity and success of indigenous
species. Within the bulk of its massive encrustations (30 cm thick
(Thorp, Pyne & West 1987)) is a protected habitat for
free-living and sessile invertebrates (C.H. Thorp pers. comm.). It
provides food: the opercula and branchial crown are eaten by fish
predators, and larvae and eggs are produced in very large numbers,
food for filter-feeders (C.H. Thorp pers. comm.).
This massive introduction, initiated almost certainly in 1976,
passed without comment until specimens were removed from the hull
of a fouled tug in 1982. Although enquiries elicited the
information that heavy tube-worm fouling had been observed in 1980,
and perhaps earlier, it was only the 'accident' of a research
student collecting fouling algae that brought the massive
encrustations to light.
Anon. 1976. Langstone Harbour study: the effect of sewage
effluent on the ecology of the harbour. Unpublished report to
Southern Water Authority by Portsmouth Polytechnic.
Crisp, D.J. 1958. The spread of Elminius modestus
Darwin in north-east Europe. Journal of the Marine Biological
Association of the United Kingdom, 37: 438-520.
Gruet, Y., Héral, M., & Robert, J.M. 1976. Premières
observations sur l'introduction de la faune associée au naissan
d'huîtres japonaises Crassostrea gigas (Thunberg), importé
sur la côte atlantique Française. Cahiers de Biologie
Marine, 17: 173-184.
Himmelman, J.H. 1980. Synchronisation of spawning in marine
invertebrates by phytoplankton. In: Invertebrate
reproduction, ed. by W.H. Clarke Jnr & T.S. Adams. 3-19.
Amsterdam, Elsevier (Developments in Endocrinology).
Imajima, M. 1976. Serpulidae (Annelida: Polychaeta) from
Japan. I. The genus Hydroides. Bulletin of the
National Museum, Tokyo, Series A (Zoology), 2:
Miura, T., & Kajihara, T. 1984. An ecological study of the
life histories of two Japanese serpulid worms, Hydroides
ezoensis and Pomatoleios kraussi. In:
Proceedings of the First International Polychaete Conference,
Sydney, Australia July 1983, ed. by P.A. Hutchings: 338-354.
The Linnaean Society of New South Wales.
Thorp, C.H. 1994. Population variation in Ficopomatus
enigmaticus (Fauvel) (Polychaeta: Serpulidae) in a brackish
water millpond at Emsworth, West Sussex, UK. Memoires de Museum
National d'Histoire Naturelle, 162: 585-591.
Thorp, C.H., Pyne, S., & West, S.A. 1987. Hydroides
ezoensis Okuda, a fouling serpulid new to British coastal
waters. Journal of Natural History, 21:
Williams, P.J. le B. 1980. Phytoplankton in Southampton Water.
In: The Solent estuarine system: an assessment of
present knowledge. 25-36. Natural Environment Research
Council, Publications Series C. No. 22.
Zibrowius, H. 1978. Introduction du polychète Serpulidae
japonaise Hydroides ezoensis sur la côte atlantique
française et remarques sur la repartition d'autres espèces de
Serpulidae. Téthys, 8: 141-150.
Zibrowius, H., & Thorp, C.H. 1989. A review of the alien
serpulid and spirorbid polychaetes in the British Isles.
Cahiers de Biologie Marine, 30: 271-285.
Acknowledgements (contributions from questionnaire)
Dr C.H. Thorp, University of Portsmouth.