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Federal Register / Vol. 86, No. 157 / Wednesday, August 18, 2021 / Rules and Regulations
prefer large rocks over other cover objects Pierce et al. 2010, p. 295, which is consistent with other studies on Eurycea habitat Bowles et al. 2006, pp. 114, 116. Larger rocks provide more suitable interstitial spaces for foraging and cover. Other studies have noted greater detection of Salado salamanders in gravels, although cobble is occupied as well Diaz and Montagne 2017, p. 10;
Diaz and Bronson-Warren, 2019, p. 7.
If springs stop flowing and the surface habitat dries up, Jollyville Plateau salamanders recede with the water table and persist in groundwater refugia until surface flow returns Bendik 2011a, p.
31. Access to refugia allows populations some resiliency against drought events. Due to the similar life history and habitats of the Georgetown and Salado salamanders, we presume that access to subsurface refugia for shelter during drought is also important for these salamanders.
Therefore, based on the information above, we identify rocky substrate, consisting of boulder, cobble, and gravel, with interstitial spaces that have minimal sediment, and access to the subsurface groundwater table to be physical or biological features essential for the cover and shelter for these species.

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Sites for Breeding, Reproduction, or Rearing or Development of Offspring Little is known about the reproductive habits of these species in the wild.
However, the Georgetown and Salado salamanders are fully aquatic, spending all of their life cycles in aquifer and spring waters. Eggs of central Texas Eurycea species are rarely seen on the surface, so it is widely assumed that eggs are laid underground Gluesenkamp 2011a, TPWD, pers.
comm.; Bendik 2011b, COA, pers.
comm..
Therefore, based on the information above, we identify access to subsurface or subterranean, water-filled voids of varying sizes e.g., caves, conduits, fractures, and interstitial spaces to be a physical or biological feature essential for breeding and reproduction for this species.
Summary of Essential Physical or Biological Features for the Georgetown and Salado Salamanders We derive the specific physical or biological features essential for the Georgetown and Salado salamanders from studies of these species habitat, ecology, and life history, as described above. We have determined that the following physical or biological features are essential to the conservation of the Georgetown and Salado salamanders:

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Georgetown Salamander 1 For surface habitat:
A Water from the Northern Segment of the Edwards Aquifer. Groundwater issuing to the surface from the underlying aquifer is similar to natural aquifer conditions as it discharges from natural spring outlets. Concentrations of water quality constituents and contaminants should be below levels that could exert direct lethal or sublethal effects such as effects to reproduction, growth, development, or metabolic processes, or indirect effects such as effects to the Georgetown salamanders prey base. Hydrologic regimes similar to the historical pattern of the specific sites are present, with at least some surface flow during the year.
The water chemistry of aquatic surface habitats is similar to natural aquifer conditions, with temperatures from 61
to 84 F 16 to 29 C, dissolved oxygen concentrations from 5 to 13 mg/L, and specific water conductance from 317 to 814 mS/cm.
B Rocky substrate with interstitial spaces. Rocks in the substrate of the salamanders surface aquatic habitat are large enough to provide salamanders with cover, shelter, and foraging habitat.
The substrate and interstitial spaces have minimal sedimentation.
C Aquatic invertebrates for food. The spring environment supports a diverse aquatic invertebrate community that includes crustaceans, insects, and aquatic snails.
D Subterranean aquifer. Access to the subsurface water table exists to provide shelter, protection, and space for reproduction. This access can occur in the form of large conduits that carry water to the spring outlet or porous voids between rocks in the streambed that extend down into the water table.
2 For subsurface habitat:
A Water from the Northern Segment of the Edwards Aquifer. Groundwater quality is similar to natural aquifer conditions. Concentrations of water quality constituents and contaminants should be below levels that could exert direct lethal or sublethal effects such as effects to reproduction, growth, development, or metabolic processes, or indirect effects such as effects to the Georgetown salamanders prey base.
Hydrologic regimes similar to the historical pattern of the specific sites are present, with continuous flow. The water chemistry is similar to natural aquifer conditions, with temperatures from 61 to 84 F 16 to 29 C, dissolved oxygen concentrations from 5 to 13 mg/
L, and specific water conductance from 317 to 814 mS/cm.
B Subsurface spaces. Voids between rocks underground are large enough to
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provide salamanders with cover, shelter, and foraging habitat. These spaces have minimal sedimentation.
C Aquatic invertebrates for food. The habitat supports an aquatic invertebrate community that includes crustaceans, insects, and aquatic snails.
Salado Salamander 1 For surface habitat:
A Water from the Northern Segment of the Edwards Aquifer. Groundwater quality issuing to the surface from the underlying aquifer is similar to natural aquifer conditions as it discharges from natural spring outlets. Concentrations of water quality constituents and contaminants are below levels that could exert direct lethal or sublethal effects such as effects to reproduction, growth, development, or metabolic processes, or indirect effects such as effects to the Salado salamanders prey base. Hydrologic regimes similar to the historical pattern of the specific sites are present, with at least some surface flow during the year. The water chemistry of aquatic surface habitats is similar to natural aquifer conditions, with temperatures from 61 to 84 F 16 to 29
C, dissolved oxygen concentrations from 5 to 13 mg/L, and specific water conductance from 317 to 814 mS/cm.
B Rocky substrate with interstitial spaces. Rocks in the substrate of the salamanders surface aquatic habitat are large enough to provide salamanders with cover, shelter, and foraging habitat.
The substrate and interstitial spaces have minimal sedimentation.
C Aquatic invertebrates for food. The spring environment is capable of supporting a diverse aquatic invertebrate community that includes crustaceans, insects, and aquatic snails.
D Subterranean aquifer. Access to the subsurface water table exists to provide shelter, protection, and space for reproduction. This access can occur in the form of large conduits that carry water to the spring outlet or porous voids between rocks in the streambed that extend down into the water table.
2 For subsurface habitat:
A Water from the Northern Segment of the Edwards Aquifer. Groundwater quality is similar to natural aquifer conditions. Concentrations of water quality constituents and contaminants are below levels that could exert direct lethal or sublethal effects such as effects to reproduction, growth, development, or metabolic processes, or indirect effects such as effects to the Salado salamanders prey base.
Hydrologic regimes similar to the historical pattern of the specific sites are present, with continuous flow. The water chemistry is similar to natural
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