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Federal Register / Vol. 86, No. 109 / Wednesday, June 9, 2021 / Rules and Regulations
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it occurs in both the Neuse and TarPamlico River basins. It is not known whether this fish also preys on waterdogs, but it is speculated that Neuse River waterdog inactivity during warmer months is in part due to the avoidance of large, predatory fishes Braswell 2005, p. 870.
Hydrilla Hydrilla verticillata, an invasive aquatic plant, alters stream habitat, decreases flows, contributes to sediment buildup in streams, and can serve as a vector for a neurotoxic cyanobacteria known to affect other vertebrates e.g., fishes, turtles, waterbirds, and their predators. High sedimentation can cause suffocation, reduce stream flow necessary for madtom and waterdog survival, smother eggs, and degrade leaf pack foraging habitat by causing prey items to abandon them. Hydrilla occurs in several watersheds where both species occur and has been recently documented from the Neuse system and the Tar River. While there are no data to indicate that hydrilla currently has population-level effects on these two species, its spread is expected to increase in the future and control or eradication is difficult.
Red swamp crayfish Procambarus clarkii is an invasive crayfish species native to the southern Mississippi River drainage in the Gulf Coastal Plain and Florida panhandle to Mexico.
Establishment of nonnative populations in eastern North Carolina are likely from release from aquaculture or from the aquarium trade Nagy et al. 2020, unpaginated. Red swamp crayfish are physical ecosystem engineers, constructing extensive burrows that can collapse stream banks and cause erosion. They are prolific opportunistic omnivores, and they not only outcompete native crayfish but also other native animals, including amphibians like Neuse River waterdog, by reducing their densities in their habitat. Recent surveys have found that when red swamp crayfish are present, Neuse River waterdogs are not Braswell, Hall, and Humphries 2020, pers. comm..
Dams and Barriers Extinction of some North American freshwater fish can be traced to impoundment and inundation of riffle habitats in all major river basins of the central and eastern United States.
Upstream of dams, the change from flowing to impounded waters, increased depths, increased buildup of sediments, decreased dissolved oxygen, and the drastic alteration in resident fish populations can threaten the survival of fish and aquatic salamanders and their
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overall reproductive success.
Downstream of dams, fluctuations in flow regimes, minimal releases and scouring flows, seasonal dissolved oxygen depletion, reduced or increased water temperatures, and changes in fish assemblages can also threaten the survival and reproduction of many aquatic species. Dams have also been identified as causing genetic segregation or isolation in river systemsresident species can no longer move freely through different habitats and may become genetically isolated from other populations throughout the river.
Improperly constructed culverts at stream crossings also can act as significant barriers and have some similar effects as dams on stream systems. Fluctuating flows through the culvert can vary significantly from the rest of the stream, preventing aquatic species passage and scouring downstream habitats. If a culvert ends up being perched above the stream bed, aquatic organisms cannot pass through it. All of the MUs containing Neuse River waterdogs and Carolina madtom populations have been impacted by dams, with as few as 11 dams in the Contentnea Creek MU to 287 dams in the Middle Neuse MU.
Energy Production and Mining The Neuse River waterdog and its habitat face impacts from oil and gas production, coal power, hydropower, and the use of biofuels. Coal mined from other States is used for energy production in North Carolina. Damage to fish and wildlife from exposure to coal ash slurry ranges from physiological, developmental, and behavioral toxicity to major populationand community-level changes.
Contamination of aquatic habitats by coal-combustion residue can result in the accumulation of metals and trace elements in larval amphibians, including arsenic, cadmium, chromium, copper, mercury, lead, selenium, and vanadium, potentially leading to developmental, behavioral, and physiological effects Rowe et al. 2002, entire. As recently as October 2016, Neuse River waterdogs in the Neuse River were exposed to coal ash slurry when Hurricane Matthew caused inundation of coal ash storage ponds.
Coal-fired power plants pump large volumes of water to produce electricity, and aquatic organisms such as larval waterdogs can be pulled in and killed unless measures are sufficient to keep organisms from being impacted. After water is used for electricity production, it is returned to surface waters, but the temperature can be considerably higher than the temperature of the stream,
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reducing the ability of the species to spawn.
Hydropower as a domestic energy source is becoming more prevalent in North Carolina, including areas where the Neuse River waterdog occurs. Like other impoundments, streams and rivers impounded by hydropower dams are changed from lotic systems to lentic systems, fragmenting habitats and disrupting movements and migrations of fish and other aquatic organisms like the Neuse River waterdog. Downstream water quality can also suffer from low dissolved oxygen levels and altered temperatures. In addition, hydropower generation can significantly change flow regimes downstream of hydropower dams, and can affect other riverine processes, such as sediment transport, nutrient cycling, and woody debris transport.
Potential impacts to both species from oil and gas extraction are numerous;
they include water quality and water quantity impacts, riparian habitat fragmentation and conversion, increased sand mining used in oil and gas extraction, and increased road and utility corridors. While oil and gas extraction currently does not, and likely will not, occur in the Tar River basin due to lack of subsurface shale deposits, impacts from shale gas extraction could occur in the Neuse River basin Service 2021b, p. 46. Future impacts from oil and gas exploration and production are certain, as North Carolina has recently begun to allow fracking operations to drill for natural gas Statewide.
Climate Change Aquatic systems are encountering changes and shifts in seasonal patterns of precipitation and runoff as a result of climate change. While both of these species have evolved in habitats that experience seasonal fluctuations in discharge, global weather patterns e.g., El Nino or La Nina can have an impact on the normal regimes. Even during naturally occurring low flow events, amphibians and fish either become stressed because they exert significant energy to move to deeper waters or they may succumb to desiccation. Because low flows in late summer and early fall are stress-inducing, droughts during this time of year result in an increase in stress and, potentially, an increased rate of mortality.
Droughts have impacted all river basins within the range of both species, from an abnormally dry ranking for North Carolina in 2001 on the Southeast Drought Monitor scale to the highest ranking of exceptionally dry for the entire range of both species in 2002 and 2007. The 2015 drought data indicated
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