Cambarus aculabrum 


Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Arthropoda Malacostraca Decapoda Cambaridae

Scientific Name: Cambarus aculabrum
Species Authority: Hobbs & Brown, 1987
Common Name(s):
English Benton County Cave Crayfish

Assessment Information [top]

Red List Category & Criteria: Critically Endangered B2ab(iii) ver 3.1
Year Published: 2010
Date Assessed: 2010-06-01
Assessor(s): Cordeiro, J., Jones, T., DiStefano, R. & Thoma, R.F.
Reviewer(s): Collen, B. & Richman, N.
Contributor(s): 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.
Cambarus aculabrum has been assessed as Critically Endangered. This species has an area of occupancy of less than 10 km² as each of the four cave pools has a maximum area of 200 m². The caves are severely fragmented and they are not connected to each other. There is a continuing decline in the extent and quality of habitat due to continued human disturbances and impacts through trampling and groundwater pollution. This species is extremely sensitive to groundwater quality and there is evidence that it is preyed on by Banded Sculpin (Cottus carolinae). It has a very low population, of only 40 individuals, and longevity of 75 years indicating that there is a late age of reproductive maturity. A recovery plan has been initiated by the USFWS in 1996, which has been implementing measures to protect this species. However, even with this recovery plan in place, the population still remains low and sensitive to disturbance and quality of habitat.
Previously published Red List assessments:
1996 Endangered (EN)

Geographic Range [top]

Range Description:

This species is known from two caves in Benton County, Arkansas, USA (Hobbs 1989, Robison and Allen 1995) and just into Missouri (Graening et al. 2006). With all of the effort to look for cave organisms based out of Fayetteville, a great deal of search has been focused in the area to find further specimens of this species. It has long seemed confined to the original caves, yet recent discoveries have added 2 additional sites nearby - both based on one or two specimens. In Missouri, expert survey work has been carried out with no further discoveries of the species in that state (Brian Wagner, AR Game and Fish, to Cindy Osborne, AR Heritage, pers. comm. 2002). The area of occupancy (AOO) is estimated to be less than 4 km².

Countries occurrence:
United States (Arkansas, Missouri)
Estimated area of occupancy (AOO) - km2: 0.4-4
Continuing decline in area of occupancy (AOO): Unknown
Extreme fluctuations in area of occupancy (AOO): Unknown
Estimated extent of occurrence (EOO) - km2:
Number of Locations: 4
Range Map: Click here to open the map viewer and explore range.

Population [top]


This species was surveyed thoroughly between 1985 and 2006, at all four caves, and a total of 40 individuals were collected (Graening et al. 2006). Two of the four sites are considered viable, one with decent viability (Graening et al. 2006).  Probably < 200 adults are extant. Numbers of crayfish observed vary dramatically between cave visits. The greatest number observed at one time in one cave is nine and in the other cave 21 (USFWS, 1996).  The current total observed population size is 40 individuals, based on the latest complete visual census of the second largest occurrence (n=6), largest occurrence (n=31), small occurrence (n=2), and the smallest creek pool discharge occurrence (n=1) (Graening et al. 2006). The maximum historical count (irrespective of date) is 56 (47 in the largest cave occurrence, 9 in the second largest cave occurrence) (Graening et al. 2006).

Current Population Trend: Unknown
Additional data:
Number of mature individuals: 40
Population severely fragmented: Yes

Habitat and Ecology [top]

Habitat and Ecology:

This species is a cave dwelling species inhabiting subterranean streams and pools (Jacobson 1996). One of the caves from which this species is known is an Ozarkian solution channel, within which this species has been observed along the side walls of a pool or at the stream margin (Robison and Allen 1995). Cave streams in which this species lives are generally less than 50 cm deep.

Systems: Freshwater

Use and Trade [top]

Use and Trade: This species is occassionally harvested by specimen collectors.

Threats [top]

Major Threat(s):

The United States Fish and Wildlife Service (USFWS 1996) recovery plan listed the following factors causing decline of the species: habitat destruction, disturbance by cavers or trespassers, specimen collection, low reproductive potential, and competition and predation by non-stygobitic species, Banded Sculpin (Cottus carolinae).  Graening et al. (2006) have assessed continuing threats since the recovery plan. Among these, habitat degradation from groundwater pollution is the primary reason for federal listing of the species and remains a serious threat.  Organic pollutants are present in the groundwater basins of the two initial caves.  Mean concentrations of nitrate, phosphorous, and faecal bacteria consistently equals or exceeds those of regional surface waters monitored by the National Water Quality Assessment Program for the Springfield Plateau Aquifer. Over 100 confined animal feeding operations (poultry and swine) and cattle ranching operations as well as over 60 residences on septic systems are within the recharge zone of one cave and two confined feeding operations, and at least 200 residences on septic systems are within the discharge zone of the second cave (Graening et al. 2006).  As for human disturbance, both caves with the largest populations were both formerly popular recreational destinations.  Vandalism and trespassing continue to be serious management issues at both sites, even after erection of steel channel gates.  Trampling was formerly considered a threat at all sites but has been alleviated at one cave when a fixed line was bolted to a canyon ledge 3 m above the stream in 2001 (Graening et al. 2006).  Another historical threat was overcollection but scientific collection has ceased and no amateur collection has been reported, probably due to federal listing in 1993 (Graening et al. 2006). More specifically, hog and poultry operations, fertilization of nearby pasture lands, regional airport expansion, and residential development threaten the water quality of the second cave. Residential development is the primary threat to water quality in the largest cave occurrence (USFWS 1996).

Conservation Actions [top]

Conservation Actions:

There is a recovery plan in place for the protection of this species compiled by the US Fish and Wildlife Service (Jacobson 1996). This plan has seen the implementation of cave gates on two sites, and three caves have surrounding land recovered and septic tanks are being upgraded to prevent leakages (NatureServe 2009). One of the localities has been designated as a National Wildlife Refuge (Jacobson 1996).

This species has been given a Global Heritage Status Rank of G1 by the American Fisheries Society (Taylor et al. 2007, NatureServe 2009). It also qualifies as endangered under the Federal Environmental Species Act of 1973 (Jacobson 1996).

Citation: Cordeiro, J., Jones, T., DiStefano, R. & Thoma, R.F. 2010. Cambarus aculabrum. The IUCN Red List of Threatened Species 2010: e.T3688A10018152. . Downloaded on 27 November 2015.
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