Cambarus aculabrum

This species was inadvertently omitted from the first edition of the AFS checklist.

Like other stygobitic species, Cambarus aculabrum is adapted to a narrow range of specific environmental conditions. Cave and karst ecosystems are especially vulnerable to changes in water quality due to shifting land use practices, including agricultural and urban development, which are pervasive across the range of this species. C. aculabrum faces other threats, including habitat disturbance and alteration, and competition from invading surface-dwelling crayfish species. In addition, this species exhibits many life history traits, including low reproductive potential, that make it intrinsically vulnerable to competition, predation, and environmental disturbance.

This species is known from three caves in Benton County, Arkansas (Hobbs 1989, USFWS 1996). An individual expelled from the groundwater during a high flow event in Washington County, Arkansas, was determined to belong to this species based on genetic sequencing (Graening et al. 2006). Another individual observed during similar circumstances in McDonald County, Missouri, in close proximity to Bear Hollow Cave was thought to potentially belong to this species as well (Graening et al. 2006).

This species is known from four recharge areas. Three of these contain traversable caves, and the fourth is a temporary upwelling in a usually dry branch from which crayfish are expelled during high flow events (Hobbs 1989; USFWS 1996; Graening et al. 2006).

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. Graening et al. (2006) assessed continuing threats since the recovery plan. 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 regularly surveyed caves. Mean concentrations of nitrate, phosphorous, and fecal bacteria consistently equal or exceed 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 recharge zone of the second cave (Graening et al., 2006). As for human disturbance, both caves with the largest populations were formerly popular recreational destinations. Vandalism and trespass continue to be serious management issues at both sites, even after erection of steel channel gates. Overcollection was historically considered a threat, but this has been greatly curtailed since federal listing of the species in 1993 (Graening et al., 2006). The caves are potentially threatened by water quality degradation, habitat alteration, disturbance by trespassers, collecting, competition, and predation. Land conversion for agriculture and residential development is a major threat across the range of this species (USFWS 1996).