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Federal Register / Vol. 86, No. 109 / Wednesday, June 9, 2021 / Rules and Regulations
physiographic variability Piedmont and Coastal Plain. Redundancy for the Neuse River waterdog is defined as multiple highly resilient populations inclusive of multiple, resilient MUs distributed throughout the species historical range. That is, highly resilient populations, coupled with a relatively broad distribution, have a positive relationship to species-level redundancy.
Current Condition of Neuse River Waterdog The historical range of the Neuse River waterdog included third and fourth order sized streams and rivers in the Tar-Pamlico, Neuse, and Trent basins, with documented historical distribution in 40 HUC10s in nine MUs across the three populations see Table 2, below. Currently, the Neuse River waterdog is extant in all nine identified MUs; however, within those MUs, it is presumed extirpated from 35 percent 14 out of 40 of the historically occupied HUC10s, and another 25
percent of the streams are in low or very low condition. Of the nine MUs, two 22
percent are estimated to have high resiliency, three 33 percent moderate resiliency, and four 45 percent low resiliency. At the population level, one of three populations Tar-Pamlico is estimated to have moderate resiliency, and two Neuse and Trent are estimated to have low resiliency.

Plain 87 percent and in the Piedmont 67 percent. However, the Piedmont has experienced significant declines in occupancy, with nearly half of the MUs losing species occurrences. Of the 16
historically occupied Piedmont HUC10s, 7 are no longer occupied, and 9 have experienced loss.
Like the madtom, the range of the Neuse River waterdog has always been very narrow, limited to the Tar-Pamlico, Trent, and Neuse River drainages.
Within the identified representation areas i.e., river basins, the species retains redundancy in terms of occupied HUC10s within the Tar-Pamlico River population 82 percent and the Neuse River population 70 percent, but 67
percent of redundancy has been lost in the Trent River population. Overall, the species has lost 27 percent 11 out of 40
historically occupied HUC10s of its redundancy across its narrow, endemic range.

Factors Influencing Viability of Neuse River Waterdog and Carolina Madtom Several natural and anthropogenic factors may impact the status of species within aquatic systems. Generally, these factors can be categorized as either environmental stressors e.g., development, agriculture practices, or forest management or systematic changes e.g., climate change, invasive species, dams or other barriers. The largest threats to the future viability of the Carolina madtom and Neuse River TABLE 2POPULATION AND MANAGEwaterdog involve habitat degradation from stressors influencing the four MENT UNIT MU NAMING FOR
habitat elements: Water quality, water NEUSE RIVER WATERDOG
quantity, instream habitat, and habitat connectivity. All of these factors are Population/management unit exacerbated by the effects of climate change. A brief summary of these Tar:
primary stressors is presented below; for Upper Tar.
Middle Tar.
a full description of these stressors, refer Lower Tar.
to chapter 4 of the SSA report for each Sandy-Swift.
species.

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Fishing Creek Subbasin.
Neuse:
Upper Neuse.
Middle Neuse.
Lower Neuse.
Trent:
Trent.

We estimated that the Neuse River waterdog currently has moderate adaptive potential, primarily due to ecological representation in three river basins and two physiographic regions.
The species retains nearly all of its known river basin variability; however, the variability within the basins is reduced compared to historical distribution. In addition, compared to historical occupancy, the species currently retains moderate physiographic variability in the Coastal
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Development and Pollution Development refers to urbanization of the landscape, and the effects of urbanization may include alterations to water quality, water quantity, and habitat both instream and streamside Service 2021ab, p. 40. Urbanization increases the amount of impervious surfaces, such as paved roads, parking lots, roofs, and even highly compacted soils like sports fields. Impervious surfaces prevent the natural soaking of rainwater into the ground and slow seepage into streams. Instead, the rainwater accumulates and flows rapidly into storm drains, which drain as runoff to local streams. This degrades stream habitat in three ways: Water quantity high flow during storms,
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water quality sediment and pollutants washing into streams, and increased water temperatures due to the surfaces heating the water. Sedimentation, including short-term storm events, has been shown to reduce survival Honeycutt et al. 2016, pp. 766767, limit juvenile abundance Bendik and Dries 2018, pp. 59165920, reduce body size Gray et al. 2004, p. 719, or result in a significant decline in aquatic salamander density in streams Welsh and Ollivier 1998, pp. 11231128;
Welsh et al. 2019, pp. 710.
Concentrations of contaminants, including nitrogen, phosphorus, salts, insecticides, polycyclic aromatic hydrocarbons, and personal care products, increase with urban development Giddings et al. 2009, p. 2;
Bringolf et al. 2010, p. 1,311. Water infrastructure development, including water supply, reclamation, and wastewater treatment, results in several pollution point discharges to streams.
Increasing urbanization results in more road development. By its nature, road development increases impervious surfaces, as well as land clearing and habitat fragmentation. Roads are generally associated with negative effects on the biotic integrity of aquatic ecosystems, including changes in surface water temperatures and patterns of runoff; sedimentation; and adding heavy metals especially lead, salts, organics, ozone, and nutrients to stream systems Trombulak and Frissell 2000, p. 18. These changes affect streamdwelling organisms such as the Carolina madtom and Neuse River waterdog by displacing them from once-preferred habitats, as well as increasing exposure and assimilation of pollutants that can result in growth defects, decreased immune response, and even death. In addition, a common impact of road development is improperly constructed culverts at stream crossings. These culverts act as barriers, either because stream flow through the culvert varies significantly from the rest of the stream or because the culvert ends up being perched, so that aquatic organisms such as these species cannot pass through them.
Carolina madtoms and Neuse River waterdogs prefer clean water with permanent flow and are not tolerant of siltation and turbidity. Benthic vertebrates, such as the madtom and waterdog, have disproportionate rates of imperilment and extirpation due to pollution because stream bottoms are often the first habitats affected, particularly by sedimentation.
Sedimentation increases embeddedness of stream substrates, making it more difficult for madtoms or salamanders to
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