First record of the alien caprellid amphipod, Caprella mutica, for the UK
ABSTRACT A large caprellid amphipod recently discovered at a salmon farm in the Lynne of Lorne near Oban, Scotland, has been identified as Caprella
mutica, a species indigenous to north-east Asia. The caprellid population appears to have become established in the last four years at the site with a high abundance of animals occurring year round on the farm nets, mooring ropes and on artificial experimental structures located <10 m from the fish farm. This paper briefly describes C.
mutica found in Scotland. Application of Chapman & Carlton's criteria for determining introduced species suggests that C.
mutica is non-indigenous to the area.
- A test of criteria for introduced species: the global invasion by the isopod Synidotea laevidorsalis (Meirs, 1881). 386-400..
- The species directory of the marinefauna and £ora of the British Isles and surroundingseas. Belfast and Ross-on-Wye:Ulster Conservation Society Zur fauna der Caprelliden der Bucht Peters des Grossen (Japanisches Meer) Suborder Caprellidea. vol II..
First record of the alien caprellid amphipod, Caprella mutica,
for the UK
K.J. Willis*P, E.J. Cook*, M. Lozano-Fernandez* and I. TakeuchiO
*Scottish Association for Marine Science (SAMS), Dunsta¡nage Marine Laboratory, Oban, Argyll, PA371QA, UK.ODepartment of
Life Environment Conservation, Faculty of Agriculture, Ehime University,Tarumi 3-5-7, Matsuyama 790-8566, Japan.
PCorresponding author, e-mail: firstname.lastname@example.org
A large caprellid amphipod recently discovered at a salmon farm in the Lynne of Lorne near Oban, Scotland, has been
identi¢ed as Caprella mutica, a species indigenous to north-east Asia. The caprellid population appears to have become
established in the last four years at the site with a high abundance of animals occurring year round on the farm nets, mooring
ropes and on arti¢cial experimental structures located 510m from the ¢sh farm. This paper brie£y describes C. mutica found
in Scotland. Application of Chapman & Carlton’s criteria for determining introduced species suggests that C. mutica is non-
indigenous to the area.
Caprella mutica is a large caprellid amphipod originally
described by Schurin (1935) from Peter the Great Bay, Siberian
coast of the Sea of Japan. The species’ natural distribution is the
coastal waters of the sub-boreal areas of north-east Asia
(Arimoto, 1976). The original description for C. mutica by
Schurin (1935) is reproduced byArimoto (1976).The description,
however, is of a small male with a body length of 12mm, hence
certain distinguishing features, which become evident in larger
adult male’s are absent, such as the middle projection on
gnathopod II which is not fully developed, and a reduced
number of £agellum articles on the ¢rst antenna. Because of the
ine⁄ciencies in the description of large C. mutica males, it is
relatively easy to mistakenly identify the species as the closely
related large Asian species Caprella acanthogaster, which is some-
times found co-occurring with C. mutica in northern Japan.
Thus, Takeuchi (1995) brie£y describes the distinctive species’
characteristics of C. mutica and C. acanthogaster collected from
Recently, specimens of a large caprellid amphipod collected
from a salmon farm situated in the Lynne of Lorne near Oban,
Scotland (56827.090’N 05827.733’W) have been identi¢ed as
C. mutica. The ¢rst record of their presence at this ¢sh farm was
in July 2000, although it is not known how long they have been
present at the site. Prior to this, Caprella mutica was unrecorded in
British waters and is not listed in the species directory of the
marine fauna and £ora of the British Isles and surrounding seas
(Howson & Picton,1997).
In this study, individuals were collected during July to
November 2002 from arti¢cial polypropylene lines (100cm
length,1.5cm diameter) positioned approximately 10m from the
salmon farm and suspended vertically in the water column at a
depth of 10m. Regular sampling at the site has recorded
abundant populations (55.38 ?26.96 ash-free dry weight gm72,
July 2002) of the caprellid.
The major distinguishing features of adult male and female
C. mutica found in Scotland are shown in Figure1. Live specimens
of C. mutica are orange to red in colour, and the brood pouch of
the female is covered with dark red spots. The body lengths of
mature adult specimens were measured using an Olympus
SZX9 stereomicroscope with a calibrated eyepiece micrometer
and are shown inTable 1. T otal body length was measured from
the basal part of antenna I on the head to the posterior end of
pereonite VII. Adult male specimens were de¢ned in this study
as greater than 11mm in length (instars 7^8). Adult females
were de¢ned as greater than 7mm in length and possessed a
fully developed brood pouch (instars 6^7). First instar juveniles
(N¼5) were also measured in November 2002 and were
recorded as attaining 1.32mm (?0.04 SD) total body length.
The ¢rst two pereonites are elongated in the male and are
densely covered with setae, with numerous small projections
present on pereonites III to VII. The second pereonite is the
longest of the seven pereonites. The ¢rst antennae of males are
slightly greater than half the body length and have a £agellum
of 20 (?2.35 SD) articles. On the male, gnathopod II arises
from the distal end of pereonite II and is also densely setose. In
large males, the middle projection is most prominent on the
grasping margin of the propodus of gnathopod II. There is no
setation on pereonites I and II in the females, which are greatly
shortened compared with the male. Gnathopod II is located
anteriorly on pereonite II of the female.
Caprella mutica has a history of accidental introductions. In the
1970s and 1980s, this species was discovered at various locations
along the Paci¢c coast of North America (Cohen & Carlton,
1995). The most probable modes of introduction were either
on shipments of Japanese oysters or in ballast water. The non-
indigenous status of a species can be assessed using Chapman &
Carlton’s criteria (1994) as follows: (1) previously unknown in
local region; (2) post-introduction range expansion; (3) human
mechanism of introduction; (4) association with known intro-
ductions; (5) association with arti¢cial or altered environments;
(6) discontinuous or restricted regional distribution; (7) disjunct
global distribution; (8) insu⁄cient life history adaptations for
global dispersal; and (9) exotic evolutionary origin. Caprella
mutica scores positively on attributes 1, 2, 3, 5, 6, 7, 8, and 9.
Thus, it is highly likely that C. mutica is a non-indigenous species
in Scotland and that it has been introduced from its native East
Asia. Although the life-history of C. mutica has not yet been
elucidated, Caprella species spend their entire life on the substrate
surface due to the absence of a planktonic larval stage; a
characteristic that illustrates the di⁄culty for global dispersal
Journal of the Marine Biological Association of the United Kingdom (2004)
J. Mar. Biol. Ass. U.K. (2004), 84,1027^1028
Printed in the United Kingdom
and supports the hypothesis that C. mutica was introduced to
Scotland from East Asia.
The caprellid amphipod fauna of the UK is relatively
depauperate compared with similar areas in the Paci¢c, with
only 22 species recorded (Howson & Picton, 1997). Of these, 11
species belong to the family Caprellidae. The Caprellidae
endemic to the UK are smaller and less robust than C. mutica
and are generally sublittoral, associated with algae, hydroids
and Bryozoa. As mentioned above, C. mutica can be de¢nitively
identi¢ed from other species of Caprella in the UK by its relative
large body size, and the presence of numerous setae and projec-
tions on the body somites. T o date, C. mutica found in Scottish
coastal waters have only been observed inhabiting arti¢cial struc-
tures, such as mooring ropes, cages, and nets associated with
aquaculture activities, and on arti¢cial structures and boat hulls
in marinas. Little is known about the biology or ecology of this
species, or its potential impact on marine ecosystems where it has
been inadvertently introduced.
We wish to thank the sta¡ from Scottish Seafarms for access to
their ¢sh farm site, andThom Nickell and Rory MacKinnon for
Arimoto, I., 1976. Taxonomic studies of caprellids (Crustacea,
Amphipoda, Caprellidae) found in the Japanese and adjacent
waters. Special Publications from the Seto Marine Biological
Laboratory, Series III, December 1976, 229 pp.
Chapman, J.W. & Carlton, J.T., 1994. A test of criteria for
introduced species: the global invasion by the isopod Synidotea
laevidorsalis (Meirs, 1881). Journal of Crustacean Biology, 11,
Cohen, A.N. & Carlton, J.T., 1995. Nonindigenous aquatic
species in a United States estuary: a case study of the bio-
logical invasions of the San Francisco Bay and delta. A Report
for the United States Fish and Wildlife Service, Washington, DC and
The National Sea Grant College Program Connecticut Sea Grant
Program, 272 pp.
Howson, C.M. & Picton, B.E., ed., 1997.The species directory of the
marinefauna and £ora of the British Isles and surroundingseas. Belfast
Schurin, A.,1935. Zur fauna der Caprelliden der Bucht Peters des
Grossen (Japanisches Meer). Zoologisches Anzeiger,122,198^203.
Takeuchi, I., 1995. Suborder Caprellidea. In Guide to seashore
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Submitted 3 November 2003. Accepted 5 March 2004.
1028K.J.Willis et al.
New caprellid for the UK
Journal of the Marine Biological Association of the United Kingdom (2004)
Table 1. Major body dimensions of adult Caprella mutica collected
from a salmon farm in the Lynne of Lorne, Scotland, during July to
November 2002. Average values are shown and the standard deviation is
shown in parentheses.
Male (N¼82) Female (N¼116)
Total body length (mm)
Minimum body length (mm)
Maximum body length (mm)
Flagellum articles (AI)
Figure 1. (A) Adult male and (B) female Caprella mutica collected o¡ a mooring buoy at a salmon farm in the Lynne of Lorne, Scotland on 1
October 2003. Total body lengths are 22.43mm (male) and 9.30mm (female). (Photograph: T.D. Nickell, SAMS)