Invasion History

First Non-native North American Tidal Record: 2000
First Non-native West Coast Tidal Record: 2000
First Non-native East/Gulf Coast Tidal Record:

General Invasion History:

Paracorophium sp. is an unidentified amphipod (possibly more than one species), belonging to a genus endemic to the Southern Hemisphere and introduced to estuaries in California (CA). Species of Paracorophium are known from New Zealand, Australia, Chile, Palau, and Thailand (Gonzalez 1986; Barnard and Karaman 1991; Fenwick 2001; Myers 2009; Wongkamhaeng et al. 2015). This amphipod was initially identified from Humboldt Bay, CA in 2000 as Chaetocorophium (=Paracorophium) lucasi, native to lakes and estuaries in New Zealand (Boyd et al. 2002). However, the identity of the species is considered unresolved (Chapman 2007; Graening et al. 2012). Paracorophium sp. has now been reported from Humboldt Bay, Tomales Bay, Elkhorn Slough, and Morro Bay, CA (Chapman 2007; Southern California Association of Marine Invertebrate Taxonomists 2008; Graening et al. 2012; California Department of Fish and Wildlife 2014). Humboldt Bay, the first site of introduction, was involved in timber trade with Chile and New Zealand, so both are plausible source areas (Boyd et al. 2002). It is possible that multiple species have been introduced (Graening et al. 2012).

North American Invasion History:

Invasion History on the West Coast:

Paracorophium sp. was first reported from Humboldt Bay, California (CA) in 2000, in muddy intertidal areas, pools and channels of salt marshes, often with freshwater input. It was found throughout the bay's shores, but was most abundant in the North Bay. This amphipod was not noted in 1980s surveys (Boyd et al. 2002). Logs from New Zealand, imported for processing in the 1970s, are considered a potential vector. There was an earlier (late 1800s) lumber trade involving exports of redwood lumber to Peru and Chile, which could have led to transport of Paracorophium in fouling or dry ballast (Boyd et al. 2002). During a restoration project on Lagunitas Creek at the headwaters of Tomales Bay, CA in 2008, Paracorophium sp. was noted as the dominant amphipod. Also in 2008, Paracorophium sp. was found in a freshwater spring flowing into Morro Bay (Southern California Association of Marine Invertebrate Taxonomists- SCAMIT 2008; Graening et al. 2012). In subsequent surveys, a single specimen was reported from Elkhorn Slough (California Department of Fish and Wildlife 2014). More than one species of Paracorophium may be present in California waters (Chapman, personal communication, cited by et al. Graening 2012).


A male specimen of Paracorophium sp. from Humboldt Bay, California is partially described and illustrated by Chapman (2007). The body of the animal is deeper, and laterally compressed, rather than depressed. Coxa plates 2-4 are taller than wide and overlap. The rostrum and ocular lobes are short. Antennae 1 and 2 are comparatively short and thin, relative to many corophiids, about 1/4 of the body length. The urosomites are fused. Uropod 3 is biramous. Article 4 of Gnathopod 2 has a narrow leaf shape, but with a blunt tip, contrasting with the pointed shape in Aoroides columbiae and A. secundus. Pereiopod 7 is elongated, as in other corophiids. Sexual dimorphism is strong in the genus, especially manifest in Gnathopod 2, which is larger in the male (Gonzalez 1986; Barnard and Karaman 1991; Fenwick 2001; Myers 2009). Adults are about 4 mm long (Chapman 2007). A detailed description of the California Paracorophium has not yet been published.

Possible candidate species include:

Paracorophium lucasi – Native to estuaries and freshwater in New Zealand (Hurley 1954).
Paracorophium excavatum – Native to New Zealand estuaries (Hurley 1954).
Paracorophium hartmanorum – Native to estuaries in Chile (Gonzalez 1986).


Taxonomic Tree

Kingdom:   Animalia
Phylum:   Arthropoda
Subphylum:   Crustacea
Class:   Malacostraca
Subclass:   Eumalacostraca
Superorder:   Peracarida
Order:   Amphipoda
Suborder:   Gammaridea
Family:   Corophiidae
Genus:   Paracorophium
Species:   sp.


Potentially Misidentified Species

Aoroides columbiae
Paracorophium sp. keys out close to Aoroides spp. in Chapman's (2007) key. Aoroides columbiae is an amphi-Pacific species (Chapman 2007).

Aoroides secundus
Paracorophium sp. keys out close to Aoroides spp. in Chapman's (2007) key. Aoroides secundus is a Northwest Pacific species, introduced to the Northeast Pacific (Chapman 2007).



Paracorophium sp. is a tube dwelling amphipod, which inhabits intertidal mudflats (Boyd et al. 2002; Chapman 2007). Gammarid amphipods have separate sexes, brooded embryos, and direct development (Bousfield 1973). In California, Paracorophium sp. occurs in muddy intertidal habitats, salt marshes, and shallow channels, often with freshwater input (Boyd et al. 2002; Graening et al. 2012). The known species of Paracorophium in New Zealand and South America live in freshwater lakes and rivers, and in estuaries of highly variable salinity (Hurley 1954; Gonzalez 1986; Fenwick 2001; Chapman et al. 2002). Like other corophiid amphipods, Paracorophium sp. probably is capable of feeding on phytoplankton, detritus and benthic microalgae on the sediment surface, and grazing on filamentous epiphytic algae growing on seaweeds and seagrasses (Bousfield 1973). Fishes and shrimps are likely predators of this amphipod.


Phytoplankton, detritus

Trophic Status:

Suspension Feeder



General HabitatTidal Fresh MarshNone
General HabitatSalt-brackish marshNone
General HabitatUnstructured BottomNone
Salinity RangeLimnetic0-0.5 PSU
Salinity RangeOligohaline0.5-5 PSU
Salinity RangeMesohaline5-18 PSU
Salinity RangePolyhaline18-30 PSU
Salinity RangeEuhaline30-40 PSU
Tidal RangeSubtidalNone
Tidal RangeLow IntertidalNone
Vertical HabitatEpibenthicNone
Vertical HabitatEndobenthicNone

Tolerances and Life History Parameters

Minimum Salinity (‰)0Field observations, Boyd et al. 2002, Chapman et al. 2002; Stevens et al. 2002; Chapman 2007
Maximum Salinity (‰)NoneNearly full salinity, Humboldt Bay (Southern California Association of Marine Inveretbrate Taxonomists (SCAMIT 2008)
Maximum Length (mm)4Chapman 2007, California. Howver, the New Zealand P. lucasi reaches 5.5 mm (Hurley 1954).
Broad Temperature RangeNoneWarm temperate-Cold temperate
Broad Salinity RangeNoneNontidal Limnetic-Polyhaline

General Impacts

No impacts have been reported for Paracorophium sp. in California.

Regional Distribution Map

Bioregion Region Name Year Invasion Status Population Status
P130 Humboldt Bay 2000 Def Estab
NEP-IV Puget Sound to Northern California 2000 Def Estab
NEP-V Northern California to Mid Channel Islands 2008 Def Estab
P070 Morro Bay 2008 Def Estab
P110 Tomales Bay 2008 Def Estab
P080 Monterey Bay 2011 Def Unk
P070 Morro Bay 2011 Def Unk
P270 Willapa Bay 2022 Def Estab

Occurrence Map

OCC_ID Author Year Date Locality Status Latitude Longitude


Barnard, J. Laurens; Karaman, Gordan S. (1991) The familes and genera of marine gammaridean Amphipoda, (except marine Gammaroidea). Part 1., Records of the Australian Museum Supplement 13: 1-417

Bousfield, E.L. (1973) <missing title>, Comstock Publishing Associates, Ithaca, NY. Pp. <missing location>

Boyd, Milton J.; Mulligan, Tim J; Shaughnessy, Frank J. (2002) <missing title>, California Department of Fish and Game, Sacramento. Pp. 1-118

California Department of Fish and Wildlife (2014) Introduced Aquatic Species in California Bays and Harbors, 2011 Survey, California Department of Fish and Wildlife, Sacramento CA. Pp. 1-36

Carlton, James T. (Ed.) (2007) The Light and Smith Manual: Intertidal Invertebrates from Central California to Oregon Fourth Edition, Completely Revised and Expanded, University of California Press, Berkeley. Pp. <missing location>

Chapman, John W. (2007) The Light and Smith Manual: Intertidal invertebrates from Central California to Oregon (4th edition), University of California Press, Berkeley CA. Pp. 545-611

Chapman, M. Ann; Hogg, Ian D.; Schnabel, Kareen E.; Stevens, Mark I. (2002) Synonymy of the New Zealand corophiid amphipod genus, Chaetocorophium, 1979, with Paracorophium, 1899: morphological and genetic evidence., Journal of the Royal Society of New Zealand 32(2): 229-241

Fenwick, Graham D. (2001) The freshwater Amphipoda (Crustacea) of New Zealand: A review, Journal of the Royal Society of New Zealand 31(2): 341-363

Gonzalez, Exequiel (1986) A new record of Paracorophium hartmannorum (Andres, Proceedings of the Biological Society of Washington 99(1): 21-28

Graening, G. O.; Rogers, D. Christopher; Holsinger, John R.; Barr, Cheryl; Bottorff, Richard (2012) Checklist of inland aquatic Amphipoda (Crustacea: Malacostraca) of California, Zootaxa 3544: 1-27

Hurley, D. E. (1954) Studies of the New Zealand Amphipodan fauna. No. 7. The family Corophiidae, including a new species of Paracorophium, Transactions of the Royal Society of New Zealand 82(2): 431-460

Knox, Matthew A.; Hogg, Ian D.; Pilditch, Conrad A. (2011) The role of vicariance and dispersal on New Zealand’s estuarine biodiversity: the case of Paracorophium (Crustacea: Amphipoda), Biological Journal of the Linnean Society 103: 863-874

Myers, Alan A. (2009) Corophiidae, Zootaxa 2260: 373-379

Schnabel, Karen E.; Hogg, Ian D.; Chapman, M. Ann (2000) Population genetic structures of two corophiid amphipods and the present of morphologically cryptic species: implications for the conservation of diversity, New Zealand Journal of Marine and Freshwater Research 34: 637-644

Southern California Association of Marine Inveretbrate Taxonomists (SCAMIT) (2008) June 27, 2008, SCAMIT Newsletter 27(1/2): 3

Stevens, Mark I.; Hogg, Ian D.; Chapman, M. Ann (2002) The corophiid amphipods of Tauranga Harbor, New Zealand: evidence of an Australian crustacean invader., Hydrobiologia 474: 147-154

Wongkamhaeng, Koraon; Nabhitabhata, Jaruwat; Towatana, Prawit (2015) Corophiine amphipods of the genera Chelicorophium and Paracorophium from the lower Gulf of Thailand (Crustacea, Amphipoda, Corophiidae, Corophiinae), ZooKeys 505: 35-50