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Federal Register / Vol. 86, No. 157 / Wednesday, August 18, 2021 / Rules and Regulations
habitats e.g., spring opening and spring run, Georgetown and Salado salamanders are generally found within 66 ft 20 m of a spring source TPWD
2011, p. 3; Diaz et al 2015, p. 7. These salamanders appear to be most abundant within the first 16 ft 5 m of a spring opening Pierce et al. 2010, p.
294; Gutierrez et al. 2018, pp. 386388;
Pierce et al. 2014, pp. 139140, 141
142. However, some researchers have noted results of their mark-recapture efforts are most applicable to large juvenile and adult Georgetown and Salado salamanders, and may not accurately depict the movement of larvae Gutierrez et al., pp. 387388.
Georgetown and Salado salamanders have been regularly observed, in reduced numbers, at distances greater than 66 ft 20 m from spring openings Pierce 2016, p. 13; Pierce 2017, p. 14, 17, 19; Gutierrez et al. 2018, p. 386.
Some individual salamanders have been found up to 194 ft 59 m from a spring opening Pierce et al. 2011a, p. 4; Pierce 2015, p. 13; Pierce 2016, pp. 14, 17, 19;
Gutierrez et al. p. 386. Gravid i.e., eggbearing Georgetown and Salado salamanders have been noted as moving more often and to greater distances than non-gravid individuals Pierce 2015, pp.
78; Gutierrez et al. 2018, pp. 385386.
Some researchers have indicated that areas downstream from spring openings may be important for salamander reproduction Pierce 2015, pp. 78;
Gutierrez et al. 2018, pp. 387388.
Jollyville Plateau salamander small juveniles were most abundant downstream from spring openings, with most of these individuals occurring at a distance of approximately 197262 ft 6080 m from spring outlets Bendik et al. 2016, pp. 910, 16.
The Jollyville Plateau salamander has been found up to 262 ft 80 m both upstream and downstream from a spring outlet Bendik et al. 2016, p. 9. That salamander species, along with the Georgetown and Salado salamanders, comprise a closely related subgenus, Septentriomolge, occurring in the Northern Segment of the Edwards Aquifer Hillis et al. 2001, pp. 275, 277;
Devitt et al. 2019, pp. 26262628.
Members of the Eurycea subgenus can travel greater distances from a discrete spring opening than previously thought, including upstream areas Bendik et al.
2016, p. 9. Therefore, we presume that the Georgetown and Salado salamanders may move a comparable distance and that aquatic habitat away from spring openings is potentially important to salamander reproduction.
Georgetown and Salado salamanders likely use the subterranean aquifer for habitat throughout the year, similar to
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other Eurycea species Bendik and Gluesenkamp 2012, pp. 45; Bendik et al. 2013, pp. 1012, 15; Bendik 2017, p.
5,013; Diaz and Bronson-Warren 2018, p. 11; Devitt et al. 2019a, p. 2,625.
Morphological forms of Georgetown salamander with cave adaptations have been found at two caves TPWD 2011, p. 8, indicating that they spend all of their lives underground at these two locations. We assume that the Salado salamander also uses subsurface areas given recruitment of individuals to the surface from the underlying aquifer, with surface recruitment at one occupied spring opening in Bell County estimated at 0.03 salamanders per day Diaz and Bronson-Warren 2019, p. 7.
Therefore, based on the information above, we identify springs, associated streams, and underground spaces within the Northern Segment of the Edwards Aquifer to be physical or biological features essential for individual and population growth and for normal behavior of the Georgetown and Salado salamanders.
Food, Water, Air, Light, Minerals, or Other Nutritional or Physiological Requirements Georgetown and Salado Salamanders No species-specific dietary study has been completed, but the diet of the Georgetown salamander is presumed to be similar to other Eurycea species, consisting of small aquatic invertebrates such as amphipods, copepods, isopods, and insect larvae reviewed in COA
2001, pp. 56. Crustaceans from the Class Ostracoda were the most commonly observed prey item for Salado salamanders Diaz and BronsonWarren 2018, pp. 8, 14. Other invertebrates consumed by the Salado salamander included amphipods, aquatic snails, and larvae of mayflies and caddisflies Diaz and BronsonWarren 2018, p. 14.
Georgetown and Salado salamanders are strictly aquatic and spend their entire lives submersed in water from the Northern Segment of the Edwards Aquifer Pierce et al. 2010, p. 296; Diaz and Bronson-Warren 2019, p. 7. These salamanders, and the prey that they feed on, require water sourced from the Edwards Aquifer at sufficient flows i.e., quantity to meet all of their physiological requirements TPWD
2011, p. 8. This water should be flowing and unchanged in chemistry, temperature, and volume from natural conditions. Currently, only a limited subset of springs inhabited by Georgetown and Salado salamanders have been assessed for water quality.
Research at additional occupied spring
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sites will aid in refining the range of suitable water quality parameters these salamanders depend upon. Our assessment of water quality parameters was restricted to a subset of relatively intact spring sites with available water quality dataspecifically, Robertson Springs in Bell County and Cobbs, Cowan, Kings Garden, Swinbank, and Twin Springs in Williamson County.
The Salado salamander occurs at five i.e., Robertson, Cobbs, Cowan, Kings Garden, and Twin Springs of these springs. The Georgetown salamander occupies Swinbank Spring. We presume that water quality parameters at these other sites are suitable for the Georgetown salamander as well given that species co-occurrence in the Northern Segment of the Edwards Aquifer. These spring sites provide some degree of a representative sample as they lie along a roughly north to south line across that segment of the Edwards Aquifer, from southern Bell County to central Williamson County.
Water temperature recorded at the six springs referenced above averaged 69
degrees Fahrenheit F 21 degrees Celsius C and ranged from 61 to 84 F
16 to 29 C Diaz et al. 2015, p. 10;
Diaz et al. 2016, p. 14; Cambrian Environmental 2016, pp. 3, 5, 7;
Cambrian Environmental 2017a, pp. 3, 5, 7; Cambrian Environmental 2017b, pp. 5, 8, 12; Diaz and Montagne 2017, p. 17; Cambrian Environmental 2018a, pp. 4, 9, 13; Cambrian Environmental 2018c, pp. 1314; Cambrian Environmental 2019a, pp. 3738;
Cambrian Environmental 2019b, pp.
295297, 329; Cambrian Environmental 2020, pp. 3536. Concentrations of 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 and Salado salamanders prey base.
Edwards Aquifer Eurycea species are adapted to a lower ideal range of oxygen saturations compared to other salamanders Turner 2009, p. 11.
However, Eurycea salamanders need dissolved oxygen concentrations to be above a certain threshold, as the related Barton Springs salamander demonstrates declining abundance with dissolved oxygen levels below 5
milligrams per liter mg/L Turner 2004, pp. 57, 10; Turner 2009, pp. 12
15. In addition, dissolved oxygen concentrations below 4.5 mg/L resulted in a number of physiological effects in the related San Marcos salamander, including decreased metabolic rates and decreased juvenile growth rates Woods et al. 2010, p. 544. Large-scale mortality
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