Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide


Caprella mutica



Caprella mutica


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Caprella mutica; male (larger) and female (smaller).  (Original image by T. Nickell.)
TitleMale and female
CaptionCaprella mutica; male (larger) and female (smaller). (Original image by T. Nickell.)
CopyrightElizabeth J. Cook
Caprella mutica; male (larger) and female (smaller).  (Original image by T. Nickell.)
Male and femaleCaprella mutica; male (larger) and female (smaller). (Original image by T. Nickell.)Elizabeth J. Cook
Experimental frame deployed west of Zeebrugge, Belgium in 2007 showing dense aggregations of Caprella mutica.
TitleDense aggregation
CaptionExperimental frame deployed west of Zeebrugge, Belgium in 2007 showing dense aggregations of Caprella mutica.
CopyrightFrancis Kerckhof
Experimental frame deployed west of Zeebrugge, Belgium in 2007 showing dense aggregations of Caprella mutica.
Dense aggregationExperimental frame deployed west of Zeebrugge, Belgium in 2007 showing dense aggregations of Caprella mutica.Francis Kerckhof


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Preferred Scientific Name

  • Caprella mutica Schurin, 1935

International Common Names

  • English: ghost shrimp; Japanese skeleton shrimp

Local Common Names

  • Netherlands: macho spookkreeftje

Summary of Invasiveness

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C. mutica was first described from sub-boreal areas of north-east Asia in 1935 (Schurin, 1935). The first reports of C. mutica outside its native habitat were from the Pacific and Atlantic coasts of North America in the 1970s (Carlton, 1979) and 1980s (Marelli, 1981; Cohen and Carlton, 1995) and it has since spread to both northern and southern hemispheres (Ashton et al., 2007a). C. mutica is one of the largest caprellid amphipods, mature males attain body lengths of up to 50 mm (Nishimura, 1995) and populations can attain densities > 300,000 individuals/m2 (Ashton, 2006). C. mutica is an aggressive species, out-competing native caprellid amphipods for space, even at low densities (Shucksmith, 2008).C. mutica is frequently associated with man-made structures and is found in abundance on boat hulls, navigation/ offshore buoys, floating pontoons and aquaculture infrastructure. It is highly likely that its dispersal is associated with vessel movements whilst attached to hull fouling. Whilst the wider environmental implications of C. mutica have not yet been confirmed, it is likely that it has an important impact on benthic and plankton communities (Cook et al., 2007b). This species is currently not present on an alert list (e.g. IUCN, ISSG) or listed as a regulated pest etc.

Taxonomic Tree

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  • Domain: Eukaryota
  •     Kingdom: Metazoa
  •         Phylum: Arthropoda
  •             Subphylum: Crustacea
  •                 Class: Malacostraca
  •                     Subclass: Eumalacostraca
  •                         Order: Amphipoda
  •                             Suborder: Caprellidea
  •                                 Family: Caprellidae
  •                                     Genus: Caprella
  •                                         Species: Caprella mutica

Notes on Taxonomy and Nomenclature

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The caprellid amphipod Caprella mutica was first described by Schurin (1935) in Peter the Great Bay, Vladivostok, Russia and was subsequently identified in the neighbouring Possjet Bay, Japan (Vassilenko, 1967) and Akkeshi Bay, Japan (Arimoto, 1976).

This species was initially described and recorded in European waters as Caprella macho by Platvoet et al. (1995), but was later confirmed to be C. mutica (Willis et al., 2004).


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C. mutica is one of the largest caprellid amphipods, mature males attain body lengths of up to 50 mm (Nishimura, 1995), whereas females are smaller and attain body lengths of up to 29 mm (Ashton, 2006). Juvenile, immature C. mutica typically range in body length from 0.81 to 7.95 mm (Ashton, 2006). Live specimens of C. mutica are pale brown to dark red in colour, and the brood pouch of the female is covered with dark red spots. The first two pereonites are elongated in the male and are densely covered with setae. The second pereonite is the longest of the seven pereonites. On the male, gnathopod 2 arises from the distal end of pereonite 2 and is also densely setose. There is no setation on the first and second pereonites in the females, which are greatly shortened compared with the male. Gnathopod two is located anteriorly on the second pereonite of the female. The third to seventh pereonites have dorsal and lateral spines and there are three spines around the base of each gill. The gills are located on pereonites 3 and 4. The antennule of the male is slightly greater than half the body length and has a flagellum of 22 (± 2 S.D.) articles. C. mutica can be definitively identified by the relative size of the three projections on the grasping margin of the propodus of gnathopod 2. In large males, the middle projection is the most prominent (Willis et al., 2004).


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C. mutica was first described from sub-boreal areas of north-east Asia and direct sequencing of mitochondrial DNA (cytochrome c oxidase subunit I gene) has confirmed that this region is the likely origin of this species (Ashton, 2006). C. mutica has been recorded in over 130 locations globally outside its native habitat (Ashton et al., 2007a; Cook et al., 2007a). The majority of sightings are from the northern hemisphere. On the Pacific coast of North America the total number of records is nine, including a record of this species on an off-shore oil platform in California. These records include sightings in latitudes from 37o30’ to 48°30’N. There is a total of five records from the Atlantic coast of North America, ranging from Connecticut to Quebec. These records include sightings from latitudes of 41.5 to 47.9°N (Ashton et al., 2007a). A total of 117 records have been collated for Europe and include sightings in the North Sea, English Channel, Irish Sea, the west coast of Scotland and Ireland and range from 49o29’N to 62o22’N and 10o4’W to 8o26’E (Cook et al., 2007a). The region with the greatest number of records was the south-western North Sea. There are presently no records for the Baltic Sea, the Iberian Peninsula or the Mediterranean Sea. The only positive sighting from the southern hemisphere is from Timaru, New Zealand (Ashton et al., 2007a).

Distribution Table

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The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Continent/Country/RegionDistributionLast ReportedOriginFirst ReportedInvasiveReferenceNotes

Sea Areas

Atlantic, NortheastWidespread2007Introduced~1994Cook et al., 2007a
Atlantic, NorthwestWidespread2004Introduced~2003Ashton et al., 2007aFirst recorded in Area 21 in 2003. Found in marinas, harbours and on mussel lines
Pacific, Eastern CentralWidespread2004Introduced~1979Ashton et al., 2007aFirst recorded in Area 77, pre-1979 from a harbour in Puget Sound. Has since spread throughout northern part of this area
Pacific, NorthwestWidespread1935Native Not invasive Schurin, 1935First recorded in Area 61 from Peter the Great Bay, subsequently recorded in 1967 and 1968 from Japan
Pacific, SouthwestLocalised2004Introduced2004Ashton et al., 2007aFirst recorded in Timaru Harbour in 2004


JapanPresentPresent based on regional distribution.
-HokkaidoPresent1968Native Not invasive Arimoto, 1976Akkashi Bay, Shikotan Island, Kunashir Island
-HonshuPresent1967Native Not invasive Vassilenko, 1967Possjet Bay, Sea of Japan

North America

CanadaPresentPresent based on regional distribution.
-New BrunswickPresent2003IntroducedAshton et al., 2007bFound on mussel lines in Passamaquody Bay
-QuebecPresent2004IntroducedAshton et al., 2007aFound on mussel lines in Chaleur Bay
USAPresentPresent based on regional distribution.
-CaliforniaPresent2004Introduced1973Ashton et al., 2007bEstablished in the 1970s
-ConnecticutPresent2003IntroducedPederson et al., 2003Found in yacht yard in Mystic
-MainePresent2003IntroducedPederson et al., 2003Found in marina in South Freeport
-OregonPresent1983IntroducedCohen and Carlton, 1995Found in Coos Bay
-WashingtonPresentPre-1979IntroducedCarlton, 1979Found in harbour in Puget Sound


BelgiumWidespread2007Introduced1998Cook et al., 2007aMainly concentrated on navigation buoys adjacent to the port of Zeebrugge
DenmarkPresent2005IntroducedCook et al., 2007aFound on the Horns Rev offshore windfarm
FrancePresent2004IntroducedCook et al., 2007aFound in harbour in Le Havre
GermanyPresent2007Introduced2004Cook et al., 2007aFound in marinas on the islands of Sylt and Helgoland off the coast of Germany
IrelandPresent2006Introduced2003Cook et al., 2007aFirst sighted on a fish farm in Bertraghboy Bay
NetherlandsWidespread2005Introduced1994Cook et al., 2007aFirst sighting in Europe
NorwayPresent2007Introduced1999Cook et al., 2007aFound in harbours and on aquaculture structures
Russian FederationPresentPresent based on regional distribution.
-Russian Far EastWidespread1935NativeSchurin, 1935First found in Peter the Great Bay, Vladivostok
UKWidespread2007Introduced2001Cook et al., 2007aFound on marina and aquaculture structures


New ZealandLocalised2004Introduced2004Ashton et al., 2007bPresent in harbour in Timaru

History of Introduction and Spread

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The first reports of C. mutica outside its native habitat were from the Pacific and Atlantic coasts of North America in the 1970s (Carlton, 1979) and 1980s (Marelli, 1981; Cohen and Carlton, 1995). It is unknown whether these records are the result of several independent cross-oceanic introductions with oyster spat (Carlton, 1979), or the result of local small-scale transport following the first introduction (Carlton, 1996). The next series of records are from Europe, with C. mutica first identified in 1994 in a harbour at Neeltje Jans in the Netherlands (M Faasse, National Museum of Natural History Naturalis, The Netherlands, personal communication, 2008). Direct sequencing of mitochondrial DNA indicates that C. mutica was introduced to Europe either directly from Asia or from the Atlantic coast of North America (Ashton, 2006). The exact mode of introduction is unknown, although it is highly likely that ballast water transport and/ or hull fouling could be involved rather than stock movements of cultured species (Cook et al., 2007b).


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Introduced toIntroduced fromYearReasonIntroduced byEstablished in wild throughReferencesNotes
Natural reproductionContinuous restocking
Atlantic, Northwest
Pacific, Northeast 1970s

Risk of Introduction

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It is highly likely that C. mutica may be accidentally introduced to South America, southern Australia, and South Africa (Ashton et al., 2007a). All these regions are within the temperature boundaries for C. mutica and they are also key areas of shipping activity. South America and Australia are particularly well linked to south-east Asia as dispersal routes for introduced species (Carlton, 1987). Within Europe, this species is likely to continue to extend its current range, but is unlikely to survive in the central and eastern Baltic Sea due to low salinities (FIMR, 2006), and based on current knowledge it is not expected to become established in the Mediterranean Sea on account of the high summer seawater temperatures (Cook et al., 2006a). Long-range distribution will most probably depend on the movement of floating artificial structures, such as commercial and recreational vessels, whilst attachment to floating marine algae may account for more localised movements (Cook et al., 2007b). It is unlikely that C. mutica will be deliberately introduced to a region.


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In the native range, C. mutica is typically associated with either attached or drifting macroalgae, including Sargassum spp. or aquaculture structures, such as the ropes used for the culture of the macroalga Undaria spp. in Otsuchi Bay (Kawashima et al., 1999). In regions outside its native range, it has been found associated with areas of anthropogenic activity, such as harbours, marinas, navigation buoys, oil rigs and aquaculture sites (Willis et al., 2004; Ashton, 2006; Kerckhof et al., 2007).

Habitat List

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Vector Principal habitat Productive/non-natural
Inshore marine Principal habitat Harmful (pest or invasive)
Inshore marine Principal habitat Natural
Inshore marine Principal habitat Productive/non-natural

Biology and Ecology

Top of page Genetics

Direct sequencing of mitochondrial DNA (cytochrome c oxidase subunit I gene) has been used to investigate genetic variation between native and non-native populations of C. mutica. Three hundred individuals were PCR-amplified, which included 51 from the native area in Japan and 249 from non-native populations. Overall, base frequencies were biased towards A and T (A = 26%, T = 36%, C = 20%, G = 18%). All unique genetic sequences for C. mutica have been deposited with GenBank (accession numbers: DQ466220-466523). The genetic divergence between non-native populations of C. mutica in the northern hemisphere indicated significant differentiation between populations in different oceanic provinces and among populations in geographic regions. A total of seven haplotypes were found in the non-native populations, indicating considerably reduced genetic diversity relative to the native populations in Japan, where 31 unique haplotypes were observed. Collectively, the Atlantic populations were shown to have a comparatively high genetic diversity and most of the populations from this oceanic province share haplotypes. The unique haplotypes present on the Pacific coast of North America indicate strong genetic differentiation and no gene flow between the Atlantic and Pacific populations (Ashton, 2006).

Reproductive Biology

Populations of C. mutica showed an increase in spring to a peak abundance in late summer (August – September), followed by a decline in population abundance during the winter in coastal waters on the west coast of Scotland. This cycle typically follows annual seawater temperatures for the region and is similar to that observed in the native habitat in the Sea of Japan (Fedotov, 1991). Juvenile C. mutica were present throughout the year on the west coast of Scotland in fish farm cages, which may indicate either continuous reproduction in this species or delayed growth of over-wintering juveniles. Females tend to dominate the population and this is most marked in autumn and winter (Ashton, 2006). Ovigerous females are found throughout the year and the number of eggs is positively related to the length of the female (Ashton, 2006). The greatest number of ovigerous females are found in the spring and summer months (April to October) (Ashton, 2006). The number of eggs per female is highly variable (min = 3, max = 363, average = 74, SD = 47.7) (Ashton, 2006). Females produce their first brood approximately 53 days post-hatching at an average body length of 8.5mm and at a seawater temperature of 13–14oC (Cook et al., 2007b). Each female has an average of two sequential broods released at approximately 20 day intervals. The maximum number of recorded hatchlings produced by a single female at a seawater temperature of 13.0 ± 0.5°C is 82. Juveniles typically emerge from the brood pouch at a body length of approximately 1.3 mm (Cook et al., 2007b).

Physiology and Phenology

C. mutica is able to survive for up to 20 days without additional food under laboratory conditions (Cook et al., 2007b) andis tolerant of a broad range of temperature and salinity conditions, with 100% mortality at 30°C (48 h LT50, 28.3 ± 0.41°C), and salinities lower than 16‰ (48 h LC50, 18.7 ± 0.24‰) over a short (48 h) exposure period (Ashton et al., 2007b). Although lethargic at low temperatures (2°C), no mortality was observed, and the species is known to survive at temperatures as low as -1.8°C. The upper LC50 was greater than the highest salinity tested (40‰), thus it is unlikely that salinity will limit the distribution of C. mutica in open coastal waters. However, the species will be excluded from brackish water environments such as the heads of sea lochs and estuaries. The physiological tolerances of C. mutica are beyond the physical conditions experienced in its native or introduced range and are thus unlikely to be the primary factors limiting its present distribution and future spread (Ashton et al., 2007a).


Caprellids are known to be opportunist feeders and to consume any readily available organic material (Keith, 1969). C. california and C. equilibria were found to consume organic detritus, diatoms, dinoflagellates and crustaceans, including other caprellids, amphipods, isopods, harpacticoid copepods and ostracods (Keith, 1969). In laboratory studies, C. mutica has been observed grazing upon the diatom Cylindrotheca fusiformis Reumann and Lewin and the macroalgae, Fucus vesiculosus L. They have also been observed actively filtering particles out of the water column using their second pair of setose antennae as filtering structures. Feeding trials with Artemia- nauplii revealed feeding rates of approximately 20 Artemia /hour for males and 13 Artemia /hour for females. Feeding rates remain constant over a period of 24 hours indicating continuous feeding throughout the day and night. Low temperatures led to a significant decline (about 60 and 50% for males and females, respectively) in feeding rates. When offered high food quantities, the average feeding rates were higher compared to when smaller quantities of food were offered (K Boos, Biologische Anstalt Helgoland, Alfred Wegener Institut for Polar- and Marine Research, Germany, personal communication, 2008).

Fatty acid analysis of the body tissue of C. mutica collected from a salmon farm, a mussel farm and mooring lines on the west coast of Scotland and reared on either the microalga, Dunaliella tertiolecta or the diatom, Phaeodactylumtricornutum in aquaria indicated that C. mutica exhibited a predominantly predatory lifestyle in the field. However, differences in fatty acid composition between treatments suggested that C. mutica is also a highly opportunistic species, consuming both non-living fish farm derived particulate material, bacteria and phytoplankton (Cook et al., 2006b).


C. mutica is typically found associated with attached macroalgae and drifting seaweeds in its native habitat, including Sargassum spp and on aquaculture structures, such as ropes for Undaria culture in Otsuchi Bay (Kawashima et al., 1999). In non-native habitats, this species typically clings to a wide range of artificial structures (aquaculture nets, ropes, pontoons, submerged lines and boat hulls) and on fouling organisms associated with these structures (including macroalgae - particularly red filamentous algae, such as Ceramium spp., hydroids, ascidians, mussels and barnacles) (Ashton, 2006; Cook et al., 2006a). In addition, studies have found that C. mutica, prefers to attach to filamentous (e.g. filamentous and branching macroalgae) and soft structures (e.g. solitary tunicates) compared with hard structures, such as bivalve shells (Shucksmith, 2008).

Environmental Requirements

See Water Tolerances.

Water Tolerances

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ParameterMinimum ValueMaximum ValueTypical ValueStatusLife StageNotes
Depth (m b.s.l.) 0.5 20 Optimum
Salinity (part per thousand) 18 35 Optimum 11-40 tolerated; 48 h LC50, 18.7 ± 0.24; upper LC50 > 40 (Ashton et al., 2007b)
Water temperature (ºC temperature) 0 22 Optimum -1.8-25 tolerated; 48 h LT50, 28.3 ± 0.41; 100% mortality at 30 (Ashton et al., 2007b)

Natural enemies

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Natural enemyTypeLife stagesSpecificityReferencesBiological control inBiological control on
Carcinus maenas Predator Adult not specific Shucksmith, 2008

Notes on Natural Enemies

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Very little information is known about the natural enemies of C. mutica. A recent study, however, has found that the European shore crab Carcinus maenas will consume large quantities of C. mutica in laboratory experiments (Shucksmith, 2008).

Means of Movement and Dispersal

Top of page Natural Dispersal (Non-Biotic)

Natural dispersal for C. mutica is likely to be limited, as this species does not have a planktonic larval stage. Free-swimming (or natural dispersal) is, therefore, likely through short-distance swimming or current-driven dispersal following disturbance from the substrate (Ashton, 2006). Small numbers of caprellids have been identified in planktonic samples from marginal seas (Takeuchi and Sawamoto, 1998) and swimming has been observed for certain caprellid species (Caine, 1980). C. mutica has also been observed swimming short distances in the laboratory and field (E Cook, Scottish Association of Marine Science, UK, personal observation, 2008), however, the maximum distance of dispersal for this method is unknown.

Vector Transmission (Biotic)  

C. mutica has been found on drifting seaweed in its native habitat (Sano et al., 2003) and on the west coast of Scotland (Ashton, 2006). It has been suggested that this mechanism is responsible for the long distance dispersal (> 1000 km) of several planktonic species (Jokiel, 1984; Helmuth et al., 1994). In a recent study on the west coast of Scotland, C. mutica was found on 27% of the drifting mats of macroalgae collected. The maximum number of individuals on one algal mat was 71, including ovigerous females and males (Ashton, 2006). It is most likely, however, that this mechanism for dispersal will be most frequent in the spring and summer months, when large quantities of algae are produced along the continental shelf (Thiel and Haye, 2006).

Accidental Introduction

Shipping has been identified as an important pathway for the transoceanic introduction of non-native species (Drake and Lodge, 2004). Many of the areas where C. mutica has been introduced are close to busy ports suggesting that ballast water transport and/ or hull fouling could be involved (Cook et al., 2007a). Living Caprella spp. have been found in ships’ ballast tanks (Carlton, 1985) and in sea-chests in a study in New Zealand (Coutts et al., 2003). Within its native environment, C. mutica may be found attached to the macroalgae Ulva spp. and the filamentous Cladophora spp. and these are regularly found attached to ships hulls (Mineur et al., 2007). It has also been seen associated with other algae at high densities on recreational boat hulls (Minchin and Holmes, 2006; G Ashton, Smithsonian Environmental Research Centre, USA and R Shucksmith, The Scottish Association for Marine Science, UK, personal communication, 2008) and in the Adriatic Sea the non-native Caprella scaura is thought to have been spread on the hulls of leisure craft (Sconfietti et al., 2005).

Stock movements of cultured species have also been identified as one means of globally spreading non-native species (Ruiz and Hewitt, 2002; Minchin, 2007). Introduction of C. mutica to the United States has been potentially linked to the importation of the Pacific Oyster, C. gigas for culture purposes (Carlton, 1987). In Europe, the Oosterschelde region in the Netherlands has received extensive shellfish imports and these movements may have been responsible for the introduction of C. mutica (Wolff, 2005). However, this region was regularly sampled between 1990 and 1995 and C. mutica was not found (M Faasse, National Museum of Natural History Naturalis, The Netherlands, personal communication, 2008). This suggests that the introduction to Europe of C. mutica is more likely to be via commercial shipping rather than stock movements of cultured species (Cook et al., 2007a).

Intentional Introduction

There are no known reports of C. mutica being intentionally introduced to an area outside its native region.

Impact Summary

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Economic/livelihood Negative
Environment (generally) Positive and negative

Economic Impact

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There are no known economic impacts related to the presence of this species.

Environmental Impact

Top of page Impact on Habitats

C. mutica is known to occur in marine protected areas in the UK (e.g. Firth of Lorne, west coast of Scotland), but the impact of this species on the habitats within these areas is unknown.

Impact on Biodiversity

C. mutica is an aggressive species and it is highly likely, that this species will displace other native amphipod species and potentially compete with sessile suspension feeders for food.Experiments have shown that C. mutica and a common UK native species of caprellid, Caprella linearis share the same preference for fine filamentous branching structures and as a result, competition for space has been observed in both laboratory and in the field.C. mutica has been observed displacing native C. linearis at low structural diversity due to its aggressive behaviour. At higher structural diversity, however, increased availability of refuges provided shelter for the native caprellid and thus enabled the two species to co-occur. 

Further experiments, regarding density dependent interactions between C. mutica and the native caprellid C. linearis on the same substrate showed that only comparatively low numbers of the non-native C. mutica are needed to displace significantly higher proportions of the native species. However, displacement activity was restricted when population abundances of C. linearis declined to relatively low densities, suggesting that C. mutica may not entirely displace C. linearis and, therefore may allow coexistence in the field.

As C. mutica inhabits predominantly artificial structures in the field at present, the impact of this species on benthic biodiversity, native species and species of conservation remains low. Whereas, the impact on plankton biodiversity maybe significant considering their high feeding rates and population densities, particularly in the summer months (Ashton, 2006), however, the scale of this impact is unknown.

Social Impact

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This is no known social impact related to the presence of this species.

Risk and Impact Factors

Top of page Invasiveness
  • Proved invasive outside its native range
  • Has a broad native range
  • Abundant in its native range
  • Highly adaptable to different environments
  • Pioneering in disturbed areas
  • Tolerant of shade
  • Capable of securing and ingesting a wide range of food
  • Highly mobile locally
  • Benefits from human association (i.e. it is a human commensal)
  • Fast growing
  • Has high reproductive potential
  • Gregarious
  • Has high genetic variability
Impact outcomes
  • Conflict
  • Modification of natural benthic communities
  • Reduced native biodiversity
  • Threat to/ loss of native species
Impact mechanisms
  • Competition - monopolizing resources
  • Fouling
  • Interaction with other invasive species
  • Predation
  • Rapid growth
Likelihood of entry/control
  • Highly likely to be transported internationally accidentally
  • Difficult to identify/detect as a commodity contaminant


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Economic Value

There is no known economic value for C. mutica.

Social Benefit

C. mutica provides no known social benefit.

Environmental Services

C. mutica provides no known environmental services.


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All unique genetic sequences for C. mutica have been deposited with GenBank (accession numbers: DQ466220-466523).

Detection and Inspection

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The main difficulty in the detection of C. mutica has been with the identification of this species prior to 2002, as little taxonomic information was available outside its native region. This problem, however, should be rectified with the inclusion of a detailed identification notes on C. mutica in Willis et al. (2004) and the inclusion of this species in the new edition of Hayward and Ryland’s ‘Handbook of the Marine Fauna of North-West Europe’ later in 2007/08. 

Similarities to Other Species/Conditions

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It is relatively easy to mistakenly identify C. mutica as the closely related Asian species Caprella acanthogaster. Detailed descriptions of the morphology of C. acanthogaster can be found in Arimoto (1976) and Guerra-Garcia and Takeuchi (2004).

Prevention and Control

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Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.


Early warning systems

No known early warning system is in place specifically for C. mutica, but as this species becomes more widely known, it is likely that it will be identified more regularly in routine surveys.

Rapid response

No known rapid response system is available to manage C. mutica.

Public awareness

In the UK, public awareness has been largely funded by a charitable trust, the Esmée Fairbairn Foundation, with support from the UK government environment agencies which has enabled the establishment of a marine non-native species website including C. mutica, production of leaflets, posters, splash-proof ID guides and popular articles and public lectures throughout the UK. Public awareness of C.mutica in other invaded regions, however, is unknown.


No known eradication attempts have been made for C. mutica.


No known containment/ zoning attempts have been made for C. mutica.


No known control programmes have been undertaken for C. mutica.

Physical/mechanical control

Potential physical methods for the control of C. mutica may include:

· Prevent growth or regularly remove fine filamentous algae from submerged structures (e.g. boat hulls, pontoons, mariculture cages, mooring lines etc.)

· Air dry artificial structures (e.g. ropes, nets etc.) for approx. 48 hrs in the early spring prior to the summer population expansion.

· Site new marina/ port developments adjacent to freshwater inflow to reduce salinity to below tolerable limits.

Biological control

Potential use of benthic predators.

Chemical control

No known chemical control.

Monitoring and Surveillance

Monitoring for C. mutica is conducted on a regular basis in the UK, Belgium and the Netherlands. A monthly monitoring programme for C. mutica at a fish farm and marina in the Lynne of Lorne, west coast of Scotland has been conducted since 2004.


No mitigation measures have been developed for C. mutica.

Gaps in Knowledge/Research Needs

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Limited factual information is available on the economic and environmental impacts and control methods for C. mutica and these areas would greatly benefit from future research.


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Arimoto I, 1976. Taxonomic studies of caprellids (Crustacea, Amphipoda, Caprellidae) found in the Japanese adjacent waters. Special publications from the Seto Marine Biological Laboratory Series III. Osaka, Japan: Nippon Printing & Publishing Co. Ltd.

Ashton GV, 2006. University of Aberdeen PhD Thesis. Aberdeen, UK: University of Aberdeen.

Ashton GV; Willis K; Burrows M; Cook EJ, 2007. Environmental tolerance of Caprella mutica: implications for its distribution as a non-native species. Marine Environmental Research, 64:305-312.

Ashton GV; Willis KJ; Cook EJ, 2007. Global distribution of the Japanese skeleton shrimp, Caprella mutica (Crustacea, Amphipoda, Caprellidae) with a detailed account of the distribution in Scotland, UK. Hydrobiologia, 590:31-41.

Caine EA, 1980. Ecology of two littoral species of caprellid amphipods (Crustacea) from Washington, USA. Marine Biology, 56:327-335.

Carlton JT, 1979. University of California PhD Thesis. Davis, USA: University of California.

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Carlton JT, 1987. Patterns of transoceanic marine biological invasions in the Pacific ocean. Bulletin of Marine Science, 41:452-465.

Carlton JT, 1996. Pattern, process and prediction in marine invasion ecology. Biological Conservation, 78:97-106.

Cohen AN; Carlton JT, 1995. Nonindigenous aquatic species in a United States Estuary: A case study of the biological invasions of the San Francisco Bay and Delta. A Report for the United States Fish and Wildlife Service, Washington DC.

Cook EJ; Black KD; Sayer MDJ; Cromey CJ; Angel DL; Spanier E; Tsemel A; Katz T; Eden N; Karakassis I; Tsapakis M; Apostolaki ET; Malej A, 2006. The influence of caged mariculture on the early development of sublittoral fouling communities: a pan-European study. ICES Journal of Marine Science, 63(4):637-649.

Cook EJ; Jahnke M; Kerckhof F; Minchin D; Faasse M; Boos K; Ashton G, 2007. European expansion of the introduced amphipod Caprella mutica Schurin 1935. Aquatic Invasions, 2(4):411-421.

Cook EJ; Shucksmith R; Ashton GV, 2006. Proceedings of the 14th International Conference on Invasive Aquatic Species, Miami, Florida, 14-19 May 2006.

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Links to Websites

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Marlin: The Marine Life Information Network for Britain and Ireland
Scottish Association for Marine Science, Invertebrate Biology and Mariculture section


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UK: Scottish Association for Marine Science, Dunstaffnage Marine Laboratory, Oban, Argyll, PA37 1QA, Oban, Scotland, UK,


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16/11/07 Original text by:

Elizabeth Cook, Scottish Association of Marine Science, Ecology Department, Dunstaffnage Marine Laboratory, Oban Argyll, Scotland, UK

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