The Nonindigenous Occurrences section of the NAS species profiles has a new structure. The section is now dynamically updated from the NAS database to ensure that it contains the most current and accurate information. Occurrences are summarized in Table 1, alphabetically by state, with years of earliest and most recent observations, and the tally and names of drainages where the species was observed. The table contains hyperlinks to collections tables of specimens based on the states, years, and drainages selected. References to specimens that were not obtained through sighting reports and personal communications are found through the hyperlink in the Table 1 caption or through the individual specimens linked in the collections tables.

Rhithropanopeus harrisii
Rhithropanopeus harrisii
(Harris mud crab)
Native Transplant

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Rhithropanopeus harrisii (Gould, 1841)

Common name: Harris mud crab

Synonyms and Other Names: Pilumnus harrisii Gould, 1841

Taxonomy: available through www.itis.govITIS logo

Identification: The following description is taken from Rathbun (1930) and Williams (1984).  Front almost straight, slightly notched; frontal margin transversely grooved, appearing double when viewed from front. First two antero-lateral teeth fused, last three dentiform.  Chelipeds unequal and dissimilar; major chela with short fixed finger and strongly curved dactyl; minor chela with longer fixed finger and relatively straight dactyl; dactyls light in color; chelipeds nearly smooth in old individuals; carpus of chelae in juveniles rough with lines and granules. Walking legs long, slender and somewhat hairy. Color brown to olive green.

Size: Williams (1984) reported males with a carapace width of 21.3 mm,

Native Range: Original range presumed to be in fresh to estuarine waters from the southwestern Gulf of St. Lawrence, Canada, through the Gulf of Mexico to Vera Cruz, Mexico (Williams 1984).

Hydrologic Unit Codes (HUCs) Explained
Interactive maps: Point Distribution Maps

Nonindigenous Occurrences: The Harris mud crab was introduced to California in 1937 and is now abundant in the brackish waters of San Francisco Bay and freshwaters of the Central Valley (Aquatic Invaders, Elkhorn Slough Foundation).  Ricketts and Calvin (1952) noted its occurrence in Coos Bay, Oregon in 1950.  Rhithropanopeus harrisii, a common resident of Texas estuaries, has recently expanded its range to freshwater reservoirs in that state (Howells 2001; Texas Parks and Wildlife).  They have been found in the E.V. Spence, Colorado City, Tradinghouse Creek, Possum Kingdom, and Lake Balmorhea reservoirs.  These occurrences are the first records of this species in freshwater inland lakes.

This crab has been introduced to various European countries including Britain, Denmark, Belgium, the Netherlands, Poland, Germany, and France, and in Russia, Romania, and Bulgaria (Christiansen 1969).  Williams (1984) noted that this crab was first observed in Europe in the Zuiderzee, The Netherlands and was confined in that area until 1936.  Established populations were noted in rivers in southern Russia in 1939 (Williams 1984).  Gadzhiev (1936) and Turoboyski (1973) reviewed distribution of this species in the Caspian and Black seas.  Mizzan and Zanella (1996) recorded this species in Italy.

Table 1. States with nonindigenous occurrences, the earliest and latest observations in each state, and the tally and names of HUCs with observations†. Names and dates are hyperlinked to their relevant specimen records. The list of references for all nonindigenous occurrences of Rhithropanopeus harrisii are found here.

StateFirst ObservedLast ObservedTotal HUCs with observations†HUCs with observations†
CA193720106Lower Sacramento; Middle San Joaquin-Lower Chowchilla; San Francisco Bay; San Joaquin Delta; San Pablo Bay; Suisun Bay
OK201120211Lake Texoma
OR195020185Coos; Siletz-Yaquina; Siuslaw; Umpqua; Wilson-Trusk-Nestuccu
TX199820229Bosque; Colorado Headwaters; Hubbard; Lake Texoma; Lower Nueces; Middle Brazos-Lake Whitney; Middle Brazos-Palo Pinto; Toyah; Upper Colorado

Table last updated 7/12/2024

† Populations may not be currently present.

Means of Introduction: Christiansen (1969) noted that the spread of this crab was probably associated with shipping, possibly in ballast or clinging to the hulls of ships.  Spread of the mud crab from California to Oregon occurred via currents during the larval stage (Petersen 2002).  Howells (2001) noted that the source of introductions to Texas reservoirs may have resulted from "bait bucket or accidental angler/boater releases" or fish stocking activities from a coastal hatchery where R. harrisii occurs naturally.

Status: Established in most areas of occurrence.

Impact of Introduction: Payen and Bonami (1979) noted that this species is a carrier of strains of the white spot baculovirus.  These viruses are extremely virulent and cause disease in penaeid shrimp and the blue crab.  In Texas, the crabs have caused fouling problems in PVC intakes to lakeshore homes and there is evidence that they have disrupted natural community structure by replacing the crayfish that are native to local lakes.

Remarks: This crab is usually associated with some type of shelter or structure including, oyster reefs, living and decaying vegetation, and various kinds of marine debris in fresh to estuarine waters(Williams 1984).  The Harris mud crab can tolerate a wide range of salinity which may explain its success in transport to other areas.  Larval development also takes place under a broad range of environmental conditions (Costlow et al. 1966). The mud crab has established breeding populations in some Texas reservoirs and the life cycle can be completed in freshwater.  Keith (2005) noted that ovigerous females, zoeae, and small juveniles have been collected in the Possum Kingdom and Tradinghouse Creek reservoirs.

References: (click for full references)

Christiansen, M.E. 1969.  Crustacea Decapoda Brachyura.  Marine Invertebrates of Scandinavia.  Universitetsforlaget, Oslo.  143 pp.

Costlow, J.D., Jr.,  C.G. Bookhout, and R. Monroe.  1966.  Studies on the larval development of the crab, Rhithropanopeus harrisii (Gould).  The effect of salinity and temperature on larval development.  Physiological Zoology 39(2):81-100.

Aquatic Invaders, Elkhorn Slough Foundation. http://www.elkhornslough.org/research/aquaticinvaders/aquatic10.htm

Gadzhiev, D.V.  1963.  Dutch crab in the Caspian Sea. (Gollandskii krab v Kaspiiskom more.)  Priroda 10:126.

Howells, R. 2001.  Introduced non-native fishes and shellfishes in Texas waters: an updated list and discussion. Texas Parks and Wildlife Department,  Management Data Series 188.

Keith, D. E.  2005.  Occurrence of the estuarine mud crab, Rhithropanopeus harrisii, in Texas reservoirs. http://www.tarleton.edu/~biology/MudCrab.html

Mizzan, L. and L. Zanella. 1996.  First record of Rhithropanopeus harrisii (Gould, 1841) (Crustacea, Decapoda, Xanthidae) in the Italian waters.  Bolletino del Museo civico di Storio naturale di Venezia 46:109-120.

Payen, G.G. and J.R. Bonami.  1979.  Mise en evidence de particles d'allure virale associees aux noyaux des cellules mesodermiques de la zone germinative testiculaire du crabe Rhithropanopeus harrisii (Gould) (Brachyura, Xanthidae).  Rev. Trav. Inst. Pech. Marit. 43:361-365.

Petersen, C.  2002.  Characterization of larval dispersal within the California Current by two estuarine crabs.  Abstract, Ecological Society of America Annual Meeting.

Rathbun, M.J.  1930.  The cancroid crabs of America of the families Euryalidae, Portunidae, Atelecyclidae, Cancridae and Xanthidae.  Smithsonian Institution, United States National Museum, Bulletin 152:1-609.

Ricketts, E.F. and J.Calvin.  1952.  Between Pacific Tides, 3rd edition.  Stanford University Press, California.  502 pp.

Turoboyski, K.  1973.  Biology and ecology of the crab Rhithropanopeus harrisii spp. tridentatus.  Marine Biology 23(4):303-313.

Williams, A.B. 1984.  Shrimps, Lobsters, and Crabs of the Atlantic Coast of the Eastern United States, Maine to Florida.  Smithsonian Institution Press, Washington, D.C.  550 pp.

Other Resources:

US Fish and Wildlife Service Ecological Risk Screening Summary for Rhithropanopeus harrisii

Author: Perry, H.

Revision Date: 8/30/2023

Citation Information:
Perry, H., 2024, Rhithropanopeus harrisii (Gould, 1841): U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, https://nas.er.usgs.gov/queries/FactSheet.aspx?SpeciesID=197, Revision Date: 8/30/2023, Access Date: 7/13/2024

This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.


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Citation information: U.S. Geological Survey. [2024]. Nonindigenous Aquatic Species Database. Gainesville, Florida. Accessed [7/13/2024].

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