U.S. FISH AND WILDLIFE SERVICE SPECIES ASSESSMENT AND LISTING PRIORITY ASSIGNMENT FORM
Scientific Name:
Ambrysus funebris
Common Name:
Nevares Spring naucorid bug
Lead region:
Region 8 (California/Nevada Region)
Information current as of:
05/06/2014
Status/Action
___ Funding provided for a proposed rule. Assessment not updated.
___ Species Assessment - determined species did not meet the definition of the endangered or threatened under the Act and, therefore, was not elevated to the Candidate status.
___ New Candidate
_X_ Continuing Candidate
___ Candidate Removal
___ Taxon is more abundant or widespread than previously believed or not subject to the degree of threats sufficient to warrant issuance of a proposed listing or continuance of candidate status
___ Taxon not subject to the degree of threats sufficient to warrant issuance of a proposed listing or continuance of candidate status due, in part or totally, to conservation efforts that remove or reduce the threats to the species
___ Range is no longer a U.S. territory
___ Insufficient information exists on biological vulnerability and threats to support listing
___ Taxon mistakenly included in past notice of review
___ Taxon does not meet the definition of "species"
___ Taxon believed to be extinct
___ Conservation efforts have removed or reduced threats ___ More abundant than believed, diminished threats, or threats eliminated.
Petition Information
_X_ Non-Petitioned
___ Petitioned
90-Day Positive:
12 Month Positive:
Did the Petition request a reclassification?
For Petitioned Candidate species:
Is the listing warranted(if yes, see summary threats below)
To Date, has publication of the proposal to list been precluded by other higher priority listing?
Explanation of why precluded:
Historical States/Territories/Countries of Occurrence:
States/US Territories: California US Counties:County information not available Countries:Country information not available
Current States/Counties/Territories/Countries of Occurrence:
States/US Territories: California US Counties: Inyo, CA Countries:Country information not available
Land Ownership:
All occurrences of the Nevares Spring naucorid bug are on Federal lands within Death Valley National Park.
Lead Region Contact:
ASST REGL DIR-ECO SVCS, Mary Grim, 916-414-6574, [email protected] Lead Field Office Contact:
VENTURA FISH AND WILDL OFC, Constance Rutherford, 805-644-1766 x306, [email protected] Biological Information
Species Description: The Nevares Spring naucorid bug, Ambrysus funebris, is a flightless, aquatic insect that is approximately 6 millimeters (0.25 inch (in)) long.
Photo Credit: Robert W. Sites, University of Missouri and Noah K. Whiteman, PhD, Harvard University, 2008.
Taxonomy:
The Nevares Spring naucorid bug was described using specimens that were collected from Nevares Spring in Inyo County, California (La Rivers 1948, p. 107). Ambrysus funebris is recognized as being a valid and current taxonomic entity according to the Integrated Taxonomic Information System (Retrieved March 30, 2012, from the Integrated Taxonomic Information System on-line database, www.itis.gov). We have carefully reviewed the available taxonomic information and conclude the species is a valid taxon. The Nevares Spring naucorid bug is one of three naucorid species that are endemic to thermal spring complexes located along or proximal to the Amargosa River drainage along the Nevada-California border (Whiteman and Sites 2008, pp. 499500).
Habitat/Life History:
Naucorids typically prefer stream riffles that are swift enough to keep sand and silt from accumulating, but not so fast that coarse, gravelly substrates are removed (La Rivers 1948, p. 107). Laboratory and in situ field studies of different naucorid species have confirmed that naucorid habitat preferences are not random, and that water velocity and substrate size play a significant role in determining animal presence or absence (Sites and Willig 1991, p. 132; Herrmann et al. 1993, p. 571). Specifically, Sada and Herbst (2006, p. 42) found that the Nevares Spring naucorid bug preferred habitats with warm water (32 degrees Celsius [89.6 Fahrenheit]), moderate current velocities (20 centimeters (cm) per second [0.66 feet (ft) per second]), moderately deep water (48 cm [23 in]), sparse cover, gravel substrate, and green algae. These studies suggest that naucorids have ecological or physiological constraints that limit their ability to persist in modified stream habitats. Water pumping or diversion activities that modify water velocities or substrate characteristics are therefore likely to affect the distribution and abundance of naucorids because they have a finite ability to use altered streams.
Naucorids are aquatic, predaceous insects that complete their entire life cycle underwater. Other than the descriptions of the five nymphal instars (stages of development) (Whiteman and Sites 2008, pp. 505507) for the Nevares Spring naucorid bug, we have no other information regarding the life history of this species. However, Ulsinger (1956, p. 201) provided a brief description of the life history of Ambrysus mormon, a closely related species, that is located in Sacramento Valley, California. Although Ambrysus mormon occupies habitat that differs from that of the Nevares Spring naucorid bug, both species likely have similar life histories. Adults of this species lay eggs in the spring, and glue them to stones. The eggs of Ambrysus mormon hatched in about 4 weeks, each of the four nymphal instars requiring 1 week and the fifth nymphal instar requiring 3 weeks. Historical Range/Distribution:
The Nevares Spring naucorid bug is limited to the Travertine Nevares Springs Complex (Complex) within the boundary of Death Valley National Park (Park). The Travertine Springs area is a province of springs that encompasses an area of approximately 35 hectares (86 acres) (Sada and Cooper 2012, p. 6). The Travertine Springs area measures 3 kilometers (km; 2 miles [mi]) long and 1.5 km (0.93 mi) wide; it includes approximately 20 springbrooks and is located 2.44.0 km (1.52.5 mi) east of the Furnace Creek Inn and Ranch resort (Ranch) and the Park headquarters building. The Nevares Spring area is 1.1 km (0.7 mi) long and 0.5 km (0.3 mi) wide and includes 14 springbrooks; it is located 8 km (5 mi) north of the Travertine Springs area in an area locally referred to as Cow Creek.
Current Range Distribution:
The current distribution of the Nevares Spring naucorid bug continues to be limited to the Complex. Data on the abundance and distribution of the Nevares Spring naucorid bug prior to the development of the water collection systems and elimination/alteration of these aquatic habitats are not available. However, several of the aquatic habitats where the insect occurred have been eliminated or substantially reduced in size. For example, Threloff (2001, p. 30) estimated that water diversion activities in the Furnace Creek area resulted in the loss of 11,150 linear meters (m) (36,581 linear ft) of stream habitat. Historically, the species likely occupied a substantial portion of the aquatic habitat that was present in the Complex where suitable micro-habitat features were present. Consequently, it is likely that the area the species now occupies is substantially smaller than what existed historically.
Eight additional aquatic invertebrate species, including one snail, a springsnail, at least two amphipods, three ostracodes, and one riffle beetle also have distributions that are endemic to the Complex (Whiteman and Sites 2008, p. 501). The Nevares Spring naucorid bug is the rarest and the only species from the Complex listed as a candidate for protection under the Endangered Species Act.
Population Estimates/Status:
The Nevares Spring naucorid bug occurs in the Complex where several water collection systems have been installed to provide water for commercial and domestic uses within the Park. These water collection systems have caused the elimination of, or alteration to, several aquatic and wetland habitats in the Furnace Creek and Cow Creek areas. The widespread loss of aquatic habitat within the Complex since the water collection systems were installed suggests the species has experienced major reductions in abundance and distribution as stream environments were eliminated or reduced in extent. The area of occupied habitat, if combined, is approximately a single acre.
Threloff (2001, p. 13) and Sada and Herbst (2006, p. 42) determined the distribution and abundance of the Nevares Spring naucorid bug in the Complex through intensive surveys. These surveys documented the presence of the species in 8 of the 20 stream habitats in the Travertine Springs area (Table 1). These same surveys documented the presence of the naucorid bug in 4 of the 14 stream habitats in the Nevares Spring area. One of the surveys demonstrated that the Nevares Spring naucorid bug occurs at low densities (Sada and Herbst 2006, p. 42). In May of 1999, the total number of aquatic invertebrates at 72 locations in the Travertine Springs area was sampled by using 10 cm by 12 cm (4 by 4.7 in) quadrats. The results showed the presence of 42,777 individuals belonging to 59 species; only 36 of these 42,777 individuals were Ambrysus funebris. Work during this same period in the Nevares Spring area documented the presence of 7,821 individuals belonging to 55 species in 31 quadrats; only 10 of these 7,821 individuals were A. funebris. These data suggest that the species is extremely rare within its limited distribution. In 2000, Whiteman and Sites (2008, pp. 502, 503) collected all five nymphal instars of the Nevares Spring naucorid bug in Furnace Creek which indicates this species was reproducing in this area.
Whiteman and Sites (2008, p. 501) indicated that the Nevares Spring naucorid bug was introduced at Texas Springs but they provided no additional information. The introduction of the Nevares Spring naucorid bug to Texas Springs likely occurred after flows were restored in the early 2000s but the area is now filled with dense vegetation. Because naucorid bugs prefer areas with sparse cover, if the Nevares Spring naucorid bug is still present at Texas Springs, its abundance is likely low (Sada 2012, pers. comm.).
Table 1. Length of stream habitats occupied by The Nevares Spring naucorid bug (Ambrysus funebris) in the Travertine Nevares Springs Complex, Death Valley National Park, California.
Threats
A. The present or threatened destruction, modification, or curtailment of its habitat or range:
The primary threat pertaining to the Nevares Spring naucorid bug is water diversion that adversely affects the amount and quality of the insects aquatic habitat. Water collection facilities have been installed at eight locations within the Complex. Seven of these facilities provide water for human use needs in the Furnace Creek area, and one facility provides potable and irrigation water to the Cow Creek area. The water users in the Furnace Creek area include the National Park Service, the Timbisha Shoshone Indian tribe, and the Ranch. Between 1987 and 2000, the Ranch consumed 92 percent of the water that was collected from the springs in the Furnace Creek area, and the National Park Service and Timbisha Shoshone Indian Tribe consumed the remainder of the water that was collected. The average combined monthly potable and nonpotable water consumption for the three water users during this period was 198,655,000 liters (L) of water per month (52,479,099 gallons (gal) of water per month) (Psomas 2001, pp. 912). In 2000, the Timbisha Shoshone Indian tribe was granted reservation status and received a water right of approximately 114 million L of water per year (30 million gal of water per year) (National Park Service 2006a, Appendix B, p. B3). If the other two water users in the Furnace Creek area continue to collect water at previous levels, this new water right will create an additional burden to collect a volume of water that has not, for the most part, previously been diverted from the local springs.
Water collection in the Furnace Creek area is governed by a 1968 Memorandum of Understanding (MOU) that was signed by the United States of America, Borax (Holdings) Limited, and Fred Harvey, Inc. (i.e., the Furnace Creek Inn and Ranch). Under this MOU, the National Park Service has the discretion to deliver water in excess of the Ranchs basic water right of approximately 58.44 L of water per second (15.44 gal of water per second) (USA 1968 in Threloff 2001, p. 31). This equates to approximately 1.84 billion L of water per year (486 million gal of water per year). The National Park Service has exercised this discretionary option in the past and, between 1990 and 1994, administrative records indicate that an average of 541 million L of water per year (143 million gal of water per year) was delivered to the Ranch above its legal entitlement (Threloff 2001, p. 31). Most of this water was used to irrigate a golf course and provide water to two flow-through swimming pools during the summer months. During the warmer months following May of each year, the total monthly water consumption by the Ranch can increase by 27,960,000 L (7,386,251 gal) as compared to the months of December and January (Threloff 2001, p. 7).
The Ranch has questioned the validity of historical records that have been used to document the amount of water that was delivered to their property; however, based on the information above, water deliveries to the Ranch have tended to increase dramatically during the summer months as compared to other months of the year when air temperatures are cooler. The Park has installed new, more sensitive flow meters at several locations in the Furnace Creek Ranch area in an effort to better quantify the amount of water that is being delivered to the Ranch.
Approximately 870,000 L of water per day (229,830 gal of water per day) are collected from the Nevares Spring water gallery in the Cow Creek area (Threloff 2001, p. 9). This equates to approximately 317 million L of water per year (84 million gal of water per year). This water is for a National Park Service employee housing and office area.
The majority of the water collection systems that have been installed in the Travertine Springs and Nevares Spring use perforated pipe galleries that were installed after the original spring sources were excavated. The National Park Service has no data on the extent of streams in the Complex prior to the development of the water collection systems. During the summer of 1999, water was diverted from the Travertine Springs water collection system to the surface environment because harmful bacteria were present in the potable water supply. The need to temporarily turn on and off various portions of the Travertine Springs water collection system allowed spring water to be released to the surface environment; this created an unprecedented opportunity to assess the effects of water diversion activities. A GPS was used to map the extent of surface water with and without water being diverted to the Furnace Creek domestic water supply. The results of the GPS mapping indicate that water diversion activities in the Furnace Creek area are collectively responsible for the loss of 11,150 linear m (36,581 linear ft) of stream habitat when the system is fully operational (Threloff 2001, p. 30). This work demonstrated that operation of the Travertine Springs water collection facilities are collectively responsible for eliminating 80 to 85 percent of the aquatic habitat that could potentially occur in that area. Approximately 80 percent of the streams in the Travertine Springs area that persist when the water collection system is operational have attributes of human disturbance (i.e., current or abandoned water diversion structures or evidence of ground disturbance) that suggest that they have been, or are adversely affected by, historical or ongoing water diversion activities.
The original spring outflow and biological community for Texas Spring were completely eliminated when the current water collection system was developed and the entire spring discharge was diverted into the Furnace Creek potable water collection system (Threloff 2001, p. 24). This action eliminated a stream habitat that probably was at least 6 km (4 mi) in length prior to its diversion. A small stream habitat 30 meters (100 feet) west of the historical Texas Spring orifice was partially restored in the mid-1990s when Park maintenance staff diverted a portion of the spring discharge to the local surface environment; however, because the Nevares Spring naucorid bug is flightless, it is unlikely the bug would re-colonize the stream.
Sada and Herbst (2006, pp. 4548) conducted an in-depth study of the effects of water diversion activities on the Complex invertebrate community. Sada and Herbst found that the presence and abundance of different aquatic invertebrate species in the Complex were affected by factors such as water velocity and depth, amount of plant cover providing diversity of light, and the size and presence of different substrates. Each of these factors is influenced by the intensity of water diversion. As water is diverted from a stream, water velocity and depth, and wetted perimeter width are reduced, which affects adjacent plant communities and the preponderance of silts and gravels along the stream bottom. The study also found trends that suggest that decreased water flow in a stream channel causes changes in the:
1. Presence or absence of endemic species, including the Nevares Spring naucorid bug; 2. Total number of aquatic invertebrate species present at a given location; 3. Relative abundance of aquatic species in the invertebrate community; and 4. Abundance of individual endemic and nonendemic aquatic invertebrate species, including the Nevares Spring naucorid bug.
The cumulative effect of removing 151197 million L (4052 million gal) of water each month from the Travertine Springs area has likely adversely affected the Nevares Spring naucorid bug such that the remaining populations of the species are relatively small, isolated, and vulnerable to extirpation. The effects of these water diversion activities are most pronounced during the summer months when more water is diverted to flowthrough swimming pools and a golf course; these water diversions coincide with a period of high evapotranspiration which causes the aquatic habitats that are occupied by the species to be most restricted and vulnerable to perturbation.
In 2008, the Park constructed a new water system for the Furnace Creek area. This new system included a strategy for restoring some aquatic habitat in the Furnace Creek area, and also included groundwater pumping wells for potable use up-gradient from the Travertine Spring Complex where the Nevares Spring naucorid bug occurs (National Park Service 2008, p. 40). The volume of water removed using the new water diversion system is the same as current withdrawals. This new system also includes a nonpotable collection gallery installed downstream from the Complex. This is being used to water the golf course and for the flow-through swimming pools. The exact effects of implementing this water diversion method to the spring system, as well as to the Nevares Spring naucorid bug, are not yet known, but the diversion of water from above the springs may change the spring discharge rate. If the diversion results in a reduction in the spring discharge rate, this would likely adversely affect the Nevares Spring naucorid bug and its habitat. Prior to installation of the system, the Park conducted pump tests, and analysis of the data indicated a possible combined flow reduction at the springs sources of just under 25 percent (Bredehoeft et al. 2005, p. 21).
Because the National Park Service is not certain of the magnitude of the effects associated with the possible flow reduction, monitoring the output of water at the spring before, during, and after construction has been conducted. In addition, the National Park Service will monitor benthic macroinvertebrates (which includes the Nevares Spring naucorid bug) twice a year at the Complex as part of their Mojave Network Inventory and Monitoring Program (Wilson 2012, in litt.). Prior to construction, Sada and Herbst (2006, pp. 910, 2632) expanded on their 2006 study by systematically researching the effects of various water discharge levels on benthic macroinvertebrate community composition at Travertine and Nevares Springs. In March 2008, Sada and Stone (unpublished study) conducted field experiments at one of the springs to assess the effects incremental reductions of spring discharge had on certain aquatic habitat characteristics (i.e., temperature, wetted width, mean water column velocity, water depth, and aquatic habitat volume) (Sada and Cooper 2012, pp. 2226). They found that the threshold at which decreasing discharge had a non-linear effect (i.e., the point where a relatively small environmental change causes a rapid change in ecosystem state) were different for each of the aquatic habitat characteristics they measured. The threshold (i.e., percentage reduction in total spring discharge) for each aquatic habitat characteristic was: greater than 30 percent for temperature; less than 10 percent for wetted width, mean water column velocity, and aquatic habitat volume; and less than 20 percent for water depth (Sada 2012, in litt.). This suggests that relatively minor decreases in discharge could result in comparatively large effects on the aquatic environment in terms of altering microhabitat availability, reducing substrate area, and decreasing primary productivity (Sada 2012, in litt.). Using this and other information, Sada and Cooper (2012, pp. 4254) recommended monitoring methods and strategies to assess the short-term and long-term effects of restoration and inform the National Park Service how to adaptively manage the springs, and they identified a threshold of spring discharge that is necessary to sustain the current community composition.
In August 2011, the Park returned surface flows to the current dry channel located south of Travertine Springs Line 2 collection gallery (Friese 2012, in litt.). The return of surface flows to this area provides the opportunity to restore historical wetland and riparian habitat and has the potential to expand available habitat for the Nevares Spring naucorid bug. However, the consequences from this new water system are still to be determined, and results should be available by the next assessment update in 2013 (Wilson 2012, in litt.).
Ground water is the Parks principal source of water for desert springs, seeps, and streams. The maintenance of the quality and quantity of ground water is critical to the survival of desert surface waters, including springs, and the habitat for the Nevares Spring naucorid bug.
The water flowing from the Travertine and Texas Springs area is supplied by an aquifer that stretches into southwestern Nevada (National Park Service 2002, p. 21). Recently, the State of Nevada has received an increasing number of permit applications to pump ground water from this aquifer. As the human population in southwestern Nevada grows, the demand for ground water and the application for permits to pump more ground water from this aquifer will grow. This additional pumping will potentially reduce the quantity and velocity of water in desert seeps, springs, and streams and reduce the habitat availability to the Nevares Spring naucorid bug.
Nonnative palms have the potential to alter those habitat properties (i.e., water velocity, depth, temperature, substrate, presence of algae) that affect the distribution and abundance of the Nevares Spring naucorid bug. Up until 2010, nonnative date palms (Phoenix dactylifera) and fan palms (Washingtonia filifera) were present in the spring habitats that are occupied by the Nevares Spring naucorid bug. In August 2010, a fire burned woody vegetation in the Travertine Springs province, and all palms were mechanically removed in February 2011 (Sada and Cooper 2012, p. 8). The Park has kept these two nonnative palms from re-establishing; however, if these efforts are suspended, these nonnative palms will likely re-establish at Travertine Springs (Friese 2012, in litt.). Nonnative palms are still present at Nevares Springs; removal of these nonnative palm trees will likely occur in 2013 (Friese 2012, in litt.). Although the effects of these plants on aquatic communities have not been documented, anecdotal observations suggest these plant species transpire water that would otherwise be available to maintain water flow within a stream channel. These plants also reduce the primary productivity within an aquatic environment by shading stream channels; this effect in turn is likely to reduce the number of prey items available to the Nevares Spring naucorid bug because overgrown stream habitats are likely to have fewer invertebrates. The presence of palm trees also tends to reduce the overall number of aquatic invertebrates in a stream channel because palm roots and fallen fronds reduce water velocities that maintain riffle habitats required by Nevares Spring naucorid bugs. Fires could also be a threat to the species. The Travertine Springs area was dramatically affected by a fire in the summer of 2010, where a majority of the riparian vegetation burned. Initial observations found that the fire decreased Nevares Spring naucorid bug abundance where the fire burned at a high intensity (i.e., where vegetation was dominated by palms), but they are continuing to do well elsewhere (i.e., where vegetation was dominated by native shrubs and salt grass). Samples of benthic macroinvertebrates were taken from the springs within the burned area; however, the results from these samples have not been analyzed (Sada 2012, pers. comm.). To date, there are no studies that have investigated the recovery of aquatic endemics in springs affected by fire.
According to recent projections, climate change in this region may result in decreased precipitation, increased temperatures, and a decrease in recharge to the groundwater system (Fisk 2010). If this occurs, the assumption is that the local aquatic ecosystem will be adversely affected, and the Nevares Spring naucorid bugs habitat will decrease even further. The amount of discharge into the springs, water velocity, and shading characteristics may be altered. Researchers are developing a groundwater flow model for portions of the Amargosa Desert and Travertine Springs area to evaluate effects on the groundwater flow system resulting from climate change (Fisk 2010, p. 1). This study should provide insight into how aquatic and riparian communities will respond to climate change.
B. Overutilization for commercial, recreational, scientific, or educational purposes:
This factor is not known to currently affect the Nevares Spring naucorid bug.
C. Disease or predation:
Naucorids are predatory animals; they consume a number of prey species that include small aquatic insects and crustaceans. At one time, Nevares Spring naucorid bugs that occurred in Furnace Creek Wash along the southern boundary of the Travertine Springs area co-occurred with nonnative mosquitofish (Gambusia affinis ). However, a flash flood in Furnace Creek Wash in 2004 may have eliminated mosquitofish from this area. Since this time, Park staff have not observed mosquitofish in Furnace Creek Wash; however, no formal surveys have been conducted (Friese 2012, in litt.). The presence of mosquitofish in Furnace Creek Wash would likely adversely affect the Nevares Spring naucorid bug by direct predation of young and adult naucorids and competition for food resources. The mosquitofish is a generalist predator (Bence 1988, p. 505; Linden and Ceck 1990, p. 115; Rupp 1996, p. 160). Field experiments that evaluated survival rates of low density mosquito larvae populations when mosquitofish were present suggest that none of the mosquito larvae persisted after a 5-hour trial period (Goodsell and Kats 1999, p. 923). Other studies have demonstrated that mosquitofish eliminate Daphnia and other invertebrate populations (Hurlbert et al.1972, p. 639). Additional field experiments have revealed that mosquitofish significantly reduce the abundance of predatory aquatic insect species that include notonectids, belostomatids, and odonates (Lawler et al.1999, p. 618). These animals are typically as large as or larger than individuals of the Nevares Spring naucorid bug. Consequently, if mosquitofish are able to prey on a large variety of aquatic invertebrates, including larger predatory insects, they are likely to eat smaller prey items such as Nevares Spring naucorid bugs. An overlap in the diet of mosquitofish and Nevares Spring naucorid bugs is also likely to exist because both species prey on aquatic invertebrate species. Collectively, these studies suggest that mosquitofish are likely to prey on Nevares Spring naucorid bugs and to compete with these insects for limited food resources.
An introduced crayfish (Procambarus sp.) is known to be present in aquatic habitats on the Ranch; these habitats are within approximately 3 km (2 mi) of streams that are occupied by the Nevares Spring naucorid bug. Studies have indicated that introduced crayfish alter vegetation communities in aquatic environments (Lodge and Lorman 1987, p. 595; Chambers et al.1990, p. 88; Creed 1994, p. 2098; Lodge et al.1994, p. 1276) and adversely affect aquatic invertebrate species through direct predation (Chambers et al.1990, p. 90; Hanson et al.1990, p. 77). Because flash flood events, although infrequent, occur in the Travertine Springs area, the potential exists for crayfish to colonize stream habitats where Nevares Spring naucorid bugs are present. At least one published account indicates that crayfish have the potential to quickly and effectively disperse into previously unoccupied habitats (Momot 1966, p. 158). In the event that crayfish disperse from the Ranch to the Travertine Springs area, they would likely reduce the limited number of the Nevares Spring naucorid bugs that inhabit the spring complex.
D. The inadequacy of existing regulatory mechanisms:
Current regulatory mechanisms do not specifically address the Nevares Spring naucorid bug or its habitat.
The species is not currently classified as a threatened, endangered, rare, or species of special concern by the State of California. The State of California is unlikely to list an invertebrate as threatened or endangered; California has listed only three invertebrate species as threatened or endangered, while 77 vertebrate taxa have been listed. The State of California has no regulations that specifically protect invertebrates from habitat loss.
The Nevares Spring naucorid bug was classified as a candidate Category 2 species in the November 1994 Animal Candidate Notice of Review. The status of the species at that time was considered to be declining. The candidate Category 2 status was discontinued in February 28, 1996 (61 FR 7596), and only Category 1 species became recognized as candidates for listing purposes. Plants and animals that were classified previously as candidate Category 2 species were considered to be those that might require special management consideration to prevent future listing as threatened or endangered. The species does not currently appear on any advisory watch list that is maintained by the State or Federal government.
The Nevares Spring naucorid bug does not have a geographic distribution that overlaps the range of another taxon that is listed as threatened or endangered. Therefore, no regulatory requirements exist to prevent adverse effects to the species aquatic habitat because it does not co-occur with a listed species.
The National Park Service Organic Act of 1916 (39 Stat. 535, 16 U.S.C. 1, as amended), states that the National Park Service shall promote and regulate the use of the Federal areas known as national parks, monuments, and reservations to conserve the scenery and the national and historic objects and the wildlife therein . . . The National Park Service Organic Act as well as National Park Service natural resources management guidelines should provide some level of protection for the Nevares Spring naucorid bug population even in the absence of listing under the Endangered Species Act; however, no current management plans or similar documents specifically mention the need to protect the Nevares Spring naucorid bug or its habitat.
The National Environmental Policy Act (NEPA) is an additional regulatory mechanism that provides for review of impacts from actions the Park Service might propose. NEPA requires Federal agencies conducting management actions to evaluate the potential impacts associated with these actions. The National Park Service Management Policies (National Park Service 2006b) document guides how the agency is to implement NEPA. Proper NEPA analysis is required regardless of the presence or absence of listed species or species formerly listed. For Park Service-directed actions, management policies also direct the Park Service to provide an extra measure of review and analysis for species of special management concern, State-listed species, and candidate species. Therefore, any proposed activities or changes in management within the Park would generally require review under NEPA, including an analysis of the impacts of the action on the Nevares Spring naucorid bug.
E. Other natural or manmade factors affecting its continued existence:
There are no identified threats under this factor known to currently affect the Nevares Spring naucorid bug.
Conservation Measures Planned or Implemented :
A conservation agreement has not been initiated; the National Park Service has not committed funds or provided documentation that would initiate the development of a conservation agreement.
The National Park Service has implemented or plans to implement several conservation measures made by the Service and as recommended by Whiteman and Sites (2008, p. 503). These conservation measures include the installation of groundwater wells for the new water collection system, monitoring discharge differences at the streams within the Complex during operation of the water wells and pumps, and removing nonnative plants at Travertine and Nevares Springs.
Other conservation measures that have been implemented at Travertine Springs include the restoration of flows. In August 2011, 0.42 cubic meters per minute (110 gal per minute) of the Travertine 2 collection was returned to its presumed natural discharge area. This was accomplished by installing valves on the collection pipes and then closing them until the Travertine 2 collection discharge was reduced by one third. The result was approximately 20 springs and seeps emerging from the Travertine 2 collection area. The springflow converges into a single channel, and then disperses into a braided pattern a short distance downstream. The length of restored springbrook is estimated to be 1,829 m (6,000 ft). Aside from temporary releases and runoff events, the Travertine 2 area has not had surface flow for nearly 90 years. The National Park Service plans to return incremental flows to the Travertine 2 collection area until all of the previously diverted water is returned to the presumed natural discharge area. The National Park Service also plans to use this method of returning flows to Travertine 3 and 4 if possible; however, this will depend on the ability of the Furnace Creek collection gallery to deliver irrigation water to the Ranch. Decreasing flow in the collection system has resulted in decreases in the water level in the Furnace Creek collection gallery. Restoration of Travertine 3 and 4 will also require an additional culvert to convey flow under Highway 190 to the Furnace Creek Wash. Following a fire in 2010, the National Park Service removed palm trees from the Travertine Springs complex. As resources permit, the National Park Service will continue its efforts to keep palms and other nonnatives from re-establishing in the complex.
At Nevares Spring, in the summer of 2010, the National Park Service drilled a well at the Nevares spring mound. The water level has been continuously monitored since the wellhead was sealed and completed. It is very likely that this well will become the water supply for Cow Creek, which will allow for the springs collection system to be removed. The aquifer serving the well also feeds the springs. However, the conversion to the well is expected to reduce diversion from the spring source by at least one-third because the flow rate of the well will be less than what is currently being captured. The National Park Service has also planned do to nonnative vegetation removal at Nevares Springs.
Summary of Threats :
The various spring habitats that are occupied by the Nevares Spring naucorid bug have experienced a variety of adverse effects that have collectively reduced the geographic range of the species and degraded the limited number of aquatic habitats where the species continues to persist. The activities that have, or will, adversely affected the status of the Nevares Spring naucorid bug include past and ongoing water diversion activities, the alteration and degradation of its habitat from the ongoing presence of nonnative plant species, fires, past and potentially ongoing predation/competition from nonnative fish species, potential future predation by nonnative crayfish, and a current lack of regulatory mechanisms that could be afforded by the State of California or the Federal government. The distribution of the Nevares Spring naucorid bug is limited to 12 small springbrooks, and the density of Nevares Spring naucorid bugs in the streams where it does occur is low. The species has specific habitat affinities that make it susceptible to decreases in water discharge, and the flightless nature of the species makes it difficult to disperse to, or colonize, new aquatic habitats. The National Park Service and State of Nevada have begun pumping activities that have the potential to affect the quality of the aquatic habitat and the velocity of the water where the Nevares Spring naucorid bug occurs. The endemism of the Nevares Spring naucorid bug, the low number of habitats that it occupies, and the diversity of factors that adversely affect the species demonstrates that the magnitude of the threats facing the species is high. The ongoing water diversions have the potential to reduce the extent of an already limited habitat area; therefore, we consider it an imminent threat to the species. We have changed classification of the immediacy of threats from non-imminent to imminent, not as a result of actual changes in the threats, but to ensure consistency in the application of the Service's listing priority process in classifying threats that are ongoing and will continue to occur as imminent. Because the Nevares Spring naucorid bug is a taxonomically recognized species, and there is a threats magnitude of high and immediacy of imminent, we have assigned a listing priority number of 2 for this species. We find that Nevares Spring naucorid bug is warranted for listing throughout all its range, and, therefore, find that it is unnecessary to analyze whether it is threatened or endangered in a significant portion of its range.
For species that are being removed from candidate status:
_____ Is the removal based in whole or in part on one or more individual conservation efforts that you determined met the standards in the Policy for Evaluation of Conservation Efforts When Making Listing Decisions(PECE)? Recommended Conservation Measures :
Whiteman and Sites (2008, p. 503) have recognized that the Nevares Spring naucorid bug is the closest species (invertebrate or vertebrate) occurring in the Complex, to being protected by the Endangered Species Act. Through their research and observations of the species and its habitat, they have come up with several recommendations for conserving the Nevares Spring naucorid bug and therefore, the Furnace Creek ecosystem. The National Park Service is or has implemented several of these recommendations. Those recommendations that have yet to be implemented include planting native plants along patches of outflows, monitoring and removing nonnative fish, including crayfish, from areas containing naucorid bugs, and using extreme care when introducing material such as gravel into streams or channels. We have no information to indicate the National Park Service is monitoring nonnative fish, or that efforts have been made to remove them from areas where they co-occur with Nevares Spring naucorid bugs. If material is introduced into the streams or channel, extreme care should be taken to ensure the particle size is identical to the existing material. Altering particle sizes within the streams will affect water velocity and depth; therefore, presence and abundance of the Nevares Spring naucorid bug and other endemic species are affected.
Recently, Sada and Cooper (2012) completed a restoration and adaptive management plan for the Furnace Creek Springs. The plan includes restoration goals and identifies indicators to assess the progress of restoration (Sada and Cooper 2012, p. 1). In general, the plan recommends:
Achieving a balance between surface flows in springbrooks, and groundwater recharge to support phreatophytes (plants with deep root systems that draw water from near the water table). Allowing vegetation to re-establish naturally and monitoring changes over time. Planting native plant species that do not readily establish. Continuing groundwater monitoring programs. Monitoring spring discharge and not decreasing spring discharge more than 20 percent of its total discharge as recorded in 2002. Implementing aquatic and riparian monitoring programs that focus on physical and biological metrics. Eliminating invasive vegetation and preventing its re-establishment. Minimizing erosion by incrementally increasing water releases over time.
Additional information describing specific restoration efforts at each spring can be found in Sada and Cooper (2012, pp. 3135, 42). Priority Table Magnitude Immediacy Taxonomy Priority
Monotypic genus 1 Imminent Species 2 Subspecies/Population 3 High Monotypic genus 4 Non-imminent Species 5 Subspecies/Population 6 Monotype genus 7 Imminent Species 8 Subspecies/Population 9 Moderate to Low Monotype genus 10 Non-Imminent Species 11 Subspecies/Population 12
Rationale for Change in Listing Priority Number:
In previous years, magnitude of threats was classified as high and immediacy of threats was classified as non-imminent for this species, resulting in an LPN of 5. However, the primary threats to this species are ongoing and thus, to ensure consistency in the application of our listing priority process, we have changed the immediacy of threats from non-imminent to imminent. Because the Nevares Spring naucorid bug is a taxonomically recognized species, and there is a threats magnitude of high and immediacy of imminent, we have assigned a listing priority number of 2 for this species.
Magnitude:
The magnitude of threats pertaining to the Nevares Spring naucorid bug is high, given the number of activities that have the potential to further reduce the insects abundance or degrade habitat quality and quantity in many or most of the remnant wetlands where the species persists. For example, if crayfish were to invade the aquatic habitats where the Nevares Spring naucorid bug occurred, the abundance of the insect would be seriously reduced below the already low levels. Because the National Park Service does not routinely conduct surveys for crayfish or other exotic aquatic species, the invasion of crayfish into habitat occupied by the Nevares Spring naucorid bug would not be detected until well after the aquatic invertebrate community had been drastically affected.
Imminence :
The primary threat to the Nevares Spring naucorid bug is water diversion that adversely affects the amount and quality of the insects aquatic habitat. The Nevares Spring naucorid bug is only known to occur in two springs, Travertine and Nevares, located in the Park. The National Park Service has constructed a new water system for the Furnace Creek area and analysis of the data from pump tests indicates a possible combined flow reduction at the springs sources of just under 25 percent. This reduction in water flows could adversely affect the species or its habitat, by further reducing its available habitat from reduced flows and water velocities. Water diversion is ongoing and thus considered an imminent threat.
__Yes__ Have you promptly reviewed all of the information received regarding the species for the purpose of determination whether emergency listing is needed? Emergency Listing Review
__No__ Is Emergency Listing Warranted?
Emergency listing is not warranted at this time because activities that are likely to extirpate all of the Nevares Spring naucorid bugs in the Complex in the next 12 months have not been identified. Also, we have identified activities that could potentially increase the Nevares Spring naucorid bug and its habitat in the next 12 months.
Description of Monitoring:
Prior to construction, Sada and Herbst expanded on their 2006 study by systematically researching the effects of various water discharge levels on benthic macroinvertebrate community composition at Travertine and Nevares Springs. They worked to identify thresholds of discharge that are necessary to sustain the current community composition as well as provide valuable information towards spring restoration objectives. In 2008, Sada and Stone conducted field experiments to assess the effects reduced spring discharge had on the aquatic habitat. Based on their findings, Sada and Cooper recommended that discharge from each spring should not decrease more than 20 percent of its total, natural discharge as recorded in 2002. Monitoring of benthic macroinvertebrates (which includes the Nevares Spring naucorid bug) will occur twice a year at the Complex. Researchers are also developing a groundwater flow model for portions of the Amargosa Desert and Travertine Springs area to evaluate effects on the groundwater flow system resulting from climate change (Fisk 2010, p. 1). This study should provide insight into how aquatic and riparian communities will respond to climate change. Staff from the Ventura Fish and Wildlife Office periodically attempt to determine if any new literature has been published for the species and will occasionally call Park staff to determine if any proposed projects may affect the status of the species.
Indicate which State(s) (within the range of the species) provided information or comments on the species or latest species assessment: none
Indicate which State(s) did not provide any information or comment:
California
State Coordination:
The State of California did not provide any information or comments on the species or latest species assessment.
Literature Cited:
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Bredehoeft, J., J. Jansen, C. Fridrich, and M. King. 2005. Impact of Pumping on the Furnace Creek Springs. Unpublished Report for the NPS. Death Valley National Park, CA
Chambers, P.A., J.M. Hanson, J.M. Burke, and E.E. Prepas. 1990. The impact of the crayfish Orconectes virilis on aquatic macrophytes. Freshwater Biology 24(1): 81 91.
Creed, R.P. 1994. Direct and indirect effects of crayfish grazing in a stream community. Ecology 759(7): 2091 2103.
Fisk, T.T., G.Pohll, D.W. Sada, and M.C. Stone. 2010. Climate Change Impacts to Groundwater, Springs Hydrology and Aquatic Communities: Amargosa Desert and Death Valley National Park, Nevada and California. EPSCoR conference poster. February 2010. http://www.nevada.edu/epscor/nsf/2010conference/Student%20Posters%20Annual%20Conf/Climate%20Change%20Impacts%20to%20Groundwater%20Springs%20Hydrology....pdf
Friese, R. 2012. Hydrologist, Death Valley National Park, Death Valley, California. Comments on the Nevares Spring naucorid bug candidate notice of review. Dated March 14, 2012.
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Hanson, J.M., P.A. Chambers, and E.E. Prepas. 1990. Selective foraging by the crayfish Orconectes virilis and its impact on macroinvertebrates. Freshwater Biology 24(1): 69 80.
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Hurlbert, S.H., J. Zedler, and D. Fairbanks. 1972. Ecosystem alteration by mosquitofish (Gambusia affinis) predation. Science 175: 639-641.
La Rivers, I. 1948. A new species of Ambrysus from Death Valley, with notes on the genus in the United States (Hemiptera: Naucoridae). Bulletin of the Southern California Academy of Science 47(3): 103 110.
Lawler, S.P., D. Dritz, T. Strange, and M. Holyoak. 1999. Effects of introduced mosquitofish and bullfrogs on the threatened California red-legged frog. Conservation Biology 13(3): 613-622.
Linden, A., and J.J. Ceck Jr. 1990. Prey selection by mosquitofish (Gambusia affinis) in California rice fields: effect of vegetation and prey species. Journal of the American Mosquito Control Association 6: 115-120.
Lodge, D.M., M.W. Kershner, J.E. Aloi, and P. Covich. 1994. Effects of an omnivorous crayfish (Orconectes rusticus) on a freshwater littoral food web. Ecology 75(5): 1265 1281.
Lodge, D.M., and J.G. Lorman. 1987. Reductions in submersed macrophyte biomass and species richness by the crayfish Orconectes rusticus. Canadian Journal of Fisheries and Aquatic Science 44(3): 591 597.
Momot, W.T. 1966. Upstream movement of crayfish in an intermittent Oklahoma stream. American Midland Naturalist 75(l): 150 159.
National Park Service. 2002. Death Valley National Park General Management Plan. April 2002. www.nps.gov/deva/parkmgmt/upload/GMP_001.pdf
National Park Service. 2006a. Reconstruction of the Furnace Creek Water Collection System. Final Environmental Impact Statement. Death Valley National Park. May 2006. 467 pp. + 9 appendices.
National Park Service. 2006b. Management Policies. 180pp. Accessed on May 23, 2012. www.nps.gov/policy/MP2006.pdf
National Park Service. 2008. Exotic Plant Management Plan and Environmental Assessment. Death Valley National Park. 130 pp. Psomas. 2001. Title I Report Death Valley National Park: Rehabilitate Travertine Spring Water System, 6 alternatives report. Report prepared for Death Valley National Park, July 17, 2001. 27 pp. + 4 appendices.
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Sada, D.W., and D.B. Herbst. 2006. Ecology of aquatic macroinvertebrates in Travertine and Nevares Springs, Death Valley National Park, California, with an examination of water diversion effects on abundance and community structure. Report prepared for Death Valley National Park. 58 pp. + 10 appendices.
Sada, D.W. April 10, 2012. Desert Research Institute, Nevada System of Higher Education, Reno, Nevada. Telephone conversation with Erin Nordin (U.S. Fish and Wildlife Service, Ventura, California) regarding the effects of fire on the Nevares Spring naucorid bug and its habitat, and the introduction of the Nevares Spring naucorid bug into Texas Springs.
Sada, D.W. Desert Research Institute, Nevada System of Higher Education, Reno, Nevada. Electronic mail regarding the effects of decreased spring discharge on aquatic habitat. Dated April 11, 2012.
Sada, D.W., and D.J. Cooper. 2012. Furnace Creek springs restoration and adaptive management plan. Death Valley, California. Report prepared for Death Valley National Park. 65 pp.
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Approval/Concurrence:
Lead Regions must obtain written concurrence from all other Regions within the range of the species before recommending changes, including elevations or removals from candidate status and listing priority changes; the Regional Director must approve all such recommendations. The Director must concur on all resubmitted 12-month petition findings, additions or removal of species from candidate status, and listing priority changes.
Approve: 06/10/2014 Date Concur: 11/06/2012 Date
Did not concur: Date
Director's Remarks: