Invasion History

First Non-native North American Tidal Record: 1997
First Non-native West Coast Tidal Record: 1997
First Non-native East/Gulf Coast Tidal Record:

General Invasion History:

Orientomysis hwanhaiensis was described from Haeju Bay, on the East China Sea, in North Korea, based on material collected in 1936 (Ii 1964, Modlin and Orsi 2000; Fukuoka and Murano 2005). It is also known from the Yellow and Bohai Seas, China (Huang 2001).

North American Invasion History:

Invasion History on the West Coast:

Orientomysis hwanhaiensis was first found in San Francisco Bay, California in 1997. It occurs from the western edge of Suisan Bay, seaward to the Golden Gate at salinities from 9 to 30.4 PSU (Modlin and Orsi 2000; Mecum 2006). It was collected once in China Camp marsh, San Pablo Bay, in October 2002, during a mysid survey (Dean et al. 2005). Its current abundance within the Bay is unknown.


Mysids are small, shrimplike crustaceans, with a cape-like carapace which covers the head and thorax, but which is not attached to the last four thoracic segments. A pair of spherical statocysts is located at the base of the inner uropods. Adult females have a ventral brood pouch (Barnes 1983; Modlin in Carlton 2007).

Orientomysis hwanhaiensis has a slender, elongated body. The anterior edge of the carapace is produced into a blunt, rounded rostrum. The posterior margin of the carapace has a curved indentation, exposing somites 7 and 8. The eyes are stalked and prominent, with kidney-shaped corneas. The abdominal segments are smooth, without furrows or folds. The distal tip of the antennal scale is rounded. In the male, a penis is located near the basipod of the 7th thoracic leg, and is 2.4X as long as wide. The exopods and endopods of the uropods are blade-like, with the lateral margin slightly concave. The endopods each have four spines between statocysts and the margin. The telson is roughly triangular, but with an undulating edge, 2.4-2.5 X as long as the greatest width. The lateral margin of the telson is armed with ~30 long spines, in the distal half, interspersed with minute spines. The apex of the telson is armed with four spines, roughly equal to the longer spines on the rest of the telson, with two or three minute spines between the larger spines. Adults are up to 12 mm in length. Description based on: Modlin and Orsi 2000; Fukuoka and Murano 2005; Mecum 2006; and Modlin, in Carlton 2007).


Taxonomic Tree

Kingdom:   Animalia
Phylum:   Arthropoda
Subphylum:   Crustacea
Class:   Malacostraca
Subclass:   Eumalacostraca
Superorder:   Peracarida
Order:   Mysidacea
Suborder:   Mysida
Family:   Mysidae
Genus:   Orientomysis
Species:   hwanhaiensis


Acanthomysis hwanhaiensis (Ii, 1964)
Orientomysis hwanhaiensis (Fukuoka & Murano, 2005)

Potentially Misidentified Species

Hyperacanthomysis longirostris
Previously known as Acanthomysis bowmani. Introduced in the San Francisco estuary, strongly associated with brackish water.

Orientomysis aspera
Previously known as Acanthomysis aspera, introduced in San Francisco Bay.



Mysids are small, shrimplike crustaceans, which tend to divide their time between epibenthic habitats and the plankton, sometimes migrating diurnally, or else making brief swims between benthic habitats. Males have a pair of penes located at the junction of the thorax and abdomen, and modified pleopods used for the transfer of spermatophores - in O. hwanhaiensis, this is pleopod 4. Adult females have a brood pouch, and give birth to juveniles, resembling miniature adults (Barnes 1983; Bowman and Orsi 1993; Modlin, in Carlton 2007).

Orientomysis hwanhaiensis is most abundant in polyhaline salinities in Japanese estuaries and San Francisco Bay, but occasionally occurs in mesohaline waters, down to 9 PSU, San Francisco estuary (Mecum 2006; Dean et al. 2005; Suzuki et al. 2009). Mysids may be epibenthic feeders, suspension feeders, predators, or omnivores (Barnes 1983). Specific information on feeding of O. hwanhaiensis is not available, but it is probably an omnivorous feeder.


Phytoplankton; Zooplankton


Fishes, decapod shrimps

Trophic Status:




General HabitatUnstructured BottomNone
Salinity RangeMesohaline5-18 PSU
Salinity RangePolyhaline18-30 PSU
Salinity RangeEuhaline30-40 PSU
Tidal RangeSubtidalNone
Vertical HabitatEpibenthicNone
Vertical HabitatPlanktonicNone

Tolerances and Life History Parameters

Minimum Salinity (‰)9.8Field data, San Francsico Bay (Modlin and Orsi 2000)
Maximum Salinity (‰)30.4Field data, San Francsico Bay (Modlin and Orsi 2000)
Minimum Length (mm)9.6Adults (Modlin and Orsi 2000)
Maximum Length (mm)11.2Adults (Modlin and Orsi 2000)
Broad Temperature RangeNoneCold temperate
Broad Salinity RangeNoneMesohaline-Euhaline

General Impacts

The current abundance of the mysid Orientomysis hwanhaiensis in San Francisco Bay is not known. No impacts have been reported for this species.

Regional Distribution Map

Bioregion Region Name Year Invasion Status Population Status
NWP-4a None 1964 Native Estab
NEP-V Northern California to Mid Channel Islands 1997 Def Estab
P090 San Francisco Bay 1997 Def Estab
P093 _CDA_P093 (San Pablo Bay) 1997 Def Estab

Occurrence Map

OCC_ID Author Year Date Locality Status Latitude Longitude


Barnes, Robert D. (1983) Invertebrate Zoology, Saunders, Philadelphia. Pp. 883

Carlton, James T. (Ed.) (2007) <missing title>, University of California Press, Berkeley. Pp. <missing location>

Dean, Amy F.; Bollens, Stephen M.; Simenstad, Charles; Cordell, Jeffery (2005) Marshes as sources or sinks of an estuarine mysid: demographic patterns and tidal flux of Neomysis kadiakensis at China Camp marsh, San Francisco estuary, Estuarine, Coastal and Shelf Science 63: 1-11

Fairey, Russell; Dunn, Roslyn; Sigala, Marco; Oliver, John (2002) Introduced aquatic species in California's coastal waters: Final Report, California Department of Fish and Game, Sacramento. Pp. <missing location>

Fukuoka, Kouki; Murano, Masaaki (2005) A revision of East Asian Acanthomysis (Crustacea: Mysida: Mysidae) and redefinition of Orientomysis, with description of a new species., Journal of Natural History 39(9): 657-708

Huang, Zongguo (Ed.), Junda Lin (Translator) (2001) Marine Species and Their Distributions in China's Seas, Krieger, Malabar, FL. Pp. <missing location>

Ii, Naoyoshi (1964) Mysidae (Crustacea), Fauna Japonica 1964: 1-610.

Mecum, W. Lee (2006) <missing title>, California Department of Fish and Game, Sacramento CA. Pp. 1-6

Modlin, Richard F. (2007) The Light and Smith Manual: Intertidal invertebrates from Central California to Oregon (4th edition), University of California, Berkeley CA. Pp. 489-485

Modlin, Richard F.; Orsi, James (2000) Range extension of Acanthomysis hwanhiaensis , 1994, to the San Francisco estary, California, and notes on its description (Crustacea: Mysidacea), Procceedings of the Biological Society of Washington 113(3): 690-693