Orconectes marchandi


Taxonomy [top]

Kingdom Phylum Class Order Family

Scientific Name: Orconectes marchandi
Species Authority: Hobbs, 1948
Common Name(s):
English Mammoth Spring Crayfish

Assessment Information [top]

Red List Category & Criteria: Near Threatened ver 3.1
Year Published: 2010
Date Assessed: 2010-06-01
Assessor(s): DiStefano, R., Schuster, G.A. & Taylor, C.A.
Reviewer(s): Collen, B. & Richman, N.
Contributor(s): Livingston, F., Livingston, F., Soulsby, A.-M., Batchelor, A., Dyer, E., Whitton, F., Milligan, H.T., Smith, J., Lutz, M.L., De Silva, R., McGuinness, S., Kasthala, G., Jopling, B., Sullivan, K. & Cryer, G.
Orconectes marchandi has been assessed as Near Threatened. This species has a highly restricted distribution with an extent of occurrence (EOO) of 2,811 km² and only known from between 5-10 locations (defined by the threat of an invasive species moving into the area). An invasive species O. neglectus is reported to be in the western part of the drainage in the South Fork of Spring River, entering the system some time between 1996 and 2000, and has been moving at a rate of 28 km over 10 years. This invasive species is known to have displaced and outcompeted Cambarus hubbsi and O. eupunctus, in an adjacent drainage. When this species makes it into the main stem of the Spring river, it is thought that it will outcompete O. marchandi as well, causing a decline in population numbers and resulting in a decline in EOO. If this proves to be the case, O. marchandi will likely qualify for a threatened category.
1996 Vulnerable

Geographic Range [top]

Range Description: This species is found in the Spring River drainage system in Lawrence, Randolf, Fulton and Sharp counties, Arkansas, and Oregon County, Missouri , USA (Pflieger 1996). Although this species is known from upwards of 20 sites (Flinders and Magoulick 2005), this is reduced to 5-10 locations based on the threat of an invasive species. The extent of occurrence of this species has been estimated at just over 2,800 km².
United States (Arkansas, Missouri)
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: This species has been collected in one instance in densities of up to 5 individuals m-2 (Flinders and Magoulick 2007).  However, this is not thought to be true across its range, where at many locations when collected, it is one of the less common species (C. Taylor, pers. comm. 2009).
Population Trend: Unknown

Habitat and Ecology [top]

Habitat and Ecology: This species inhabits clear streams with riffles and runs, with gravel or rubble substrate (Pflieger 1996), but is also found in high numbers in pools and spring fed streams (Dukat and Magoulick 1999). In some parts of its range this species is found in higher numbers in non-permanent freshwater habitats than it is in those which are permanent (Flinders and Magoulic 2003).
Systems: Freshwater

Threats [top]

Major Threat(s): This species is under threat from the invasive species Orconectes neglectus, which has entered the South fork of the Spring River drainage and is rapidly spreading (B. DiStefano, pers. comm. 2009). It has already displaced two species, Cambarus hobbsi and O. eupunctus, after entering the system some time between 1990 and 2000, and has been moving at a rate of 28 km over 10 years. It is not yet present in the range of this species, but is getting closer (B. DiStefano, pers. comm. 2009).

Conservation Actions [top]

Conservation Actions: This species has been given assigned a Global Heritage Status Rank of G2 by NatureServe (Taylor et al. 2007, NatureServe 2009) and 'threatened' by the American Fisheries Society (Taylor et al. 2007). Further research and monitoring on this species is recommended to clarify threats posed. 

Citation: DiStefano, R., Schuster, G.A. & Taylor, C.A. 2010. Orconectes marchandi. The IUCN Red List of Threatened Species. Version 2014.3. <>. Downloaded on 27 March 2015.
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