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Federal Register / Vol. 86, No. 171 / Wednesday, September 8, 2021 / Rules and Regulations
necessary to maintain benthic habitats where the species is found and to maintain connectivity of streams with the floodplain, allowing the exchange of nutrients and sediment for maintenance of the crayfishs habitat and food availability.
3 Appropriate water and sediment quality including, but not limited to, conductivity; hardness; turbidity;
temperature; pH; and minimal levels of ammonia, heavy metals, pesticides, animal waste products, and nitrogen, phosphorus, and potassium fertilizers necessary to sustain natural physiological processes for normal behavior, growth, and viability of all life stages.
4 Prey base of aquatic macroinvertebrates and detritus. Prey items may include, but are not limited to, insect larvae, snails and their eggs, fish and their eggs, and plant and animal detritus.

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Special Management Considerations or Protection When designating critical habitat, we assess whether the specific areas within the geographical area occupied by the species at the time of listing contain features that are essential to the conservation of the species and which may require special management considerations or protection. The features essential to the conservation of the slenderclaw crayfish may require special management considerations or protections to reduce the following threats: 1 Impacts from invasive species, including the nonnative virile crayfish; 2 nutrient pollution from agricultural activities that impact water quantity and quality; 3 significant alteration of water quality and water quantity, including conversion of streams to impounded areas; 4 culvert and pipe installation that creates barriers to movement; and 5 other watershed and floodplain disturbances that release sediments or nutrients into the water.
Management activities that could ameliorate these threats include, but are not limited to: Control and removal of introduced invasive species; limiting the spreading of poultry litter to time periods of dry, stable weather conditions; use of best management practices designed to reduce sedimentation, erosion, and bank side destruction; protection of riparian corridors and retention of sufficient canopy cover along banks; moderation of surface and ground water withdrawals to maintain natural flow regimes; and reduction of other watershed and floodplain disturbances
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that release sediments, pollutants, or nutrients into the water.
Criteria Used To Identify Critical Habitat As required by section 4b2 of the Act, we use the best scientific data available to designate critical habitat. In accordance with the Act and our implementing regulations at 50 CFR
424.12b, we review available information pertaining to the habitat requirements of the species and identify specific areas within the geographical area occupied by the species at the time of listing and any specific areas outside the geographical area occupied by the species to be considered for designation as critical habitat.
The current distribution of the slenderclaw crayfish is much reduced from its historical distribution in one Short Creek watershed of the two populations. The currently occupied sites in the Short Creek watershed occur in a single tributary Shoal Creek, and one catastrophic event could impact this entire population. In addition, the nonnative virile crayfish occupies sites within the Short Creek watershed, including the type locality for the slenderclaw crayfish in Short Creek in which the slenderclaw crayfish no longer occurs. We anticipate that recovery will require continued protection of existing populations and habitat, as well as establishing sites in additional streams that more closely approximate its historical distribution in order to ensure there are adequate numbers of crayfish in stable populations and that these populations have multiple sites occurring in at least two streams within each watershed.
This goal will help ensure that catastrophic events, such as a chemical spill, cannot simultaneously affect all known populations.
Sources of data for this critical habitat designation include numerous survey reports on streams throughout the species range and databases maintained by crayfish experts and universities Bouchard and Hobbs 1976, entire;
Bearden 2017, unpublished data;
Schuster 2017, unpublished data; Taylor 2017, unpublished data; Service 2018, entire. We have also reviewed available information that pertains to the habitat requirements of this species. Sources of information on habitat requirements include surveys conducted at occupied sites and published in agency reports, and data collected during monitoring efforts.
Areas Occupied at the Time of Listing For locations within the geographic area occupied by the species at the time
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of listing, we identified stream channels that currently support populations of the slenderclaw crayfish. We defined current as stream channels with observations of the species from 2009 to the present. Due to the recent breadth and intensity of survey efforts for the slenderclaw crayfish throughout the historical range of the species, it is reasonable to assume that streams with no positive surveys since 2009 should not be considered occupied for the purpose of our analysis. Within these areas, we delineated critical habitat unit boundaries using the following process:
We evaluated habitat suitability of stream channels within the geographical area occupied at the time of listing, and retained for further consideration those streams that contain one or more of the physical or biological features to support life-history functions essential to conservation of the species. We refined the starting and ending points of units by evaluating the presence or absence of appropriate physical or biological features. We selected the headwaters as upstream cutoff points for each stream and downstream cutoff points that omit areas that are not suitable habitat. For example, the Guntersville Lake Tennessee Valley Authority project boundary was selected as an endpoint for one unit, as there was a change to unsuitable parameters e.g., impounded waters.
Based on this analysis, the following streams meet criteria for areas occupied by the species at the time of listing:
Bengis Creek, Scarham Creek, Shoal Creek, Short Creek, Town Creek, and Whippoorwill Creek see Unit Descriptions, below. This list does not include all stream segments known to have been occupied by the species historically; rather, it includes only the occupied stream segments within the historical range that have also retained one or more of the physical or biological features that will allow for the maintenance and expansion of existing populations.
Areas Outside the Geographical Area Occupied at the Time of Listing To consider for designation areas not occupied by the species at the time of listing, we must demonstrate that these areas are essential for the conservation of the species. To determine if these areas are essential for the conservation of the slenderclaw crayfish, we considered the life history, status, habitat elements, and conservation needs of the species such as:
1 The importance of the stream to the overall status of the species, the importance of the stream to the prevention of extinction, and the
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