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Daily Rules, Proposed Rules, and Notices of the Federal Government

DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

[Docket No. FWS-R8-ES-2011-0076: 4500030113]

Endangered and Threatened Wildlife and Plants; 12-Month Finding on a Petition To List 14 Aquatic Mollusks as Endangered or Threatened

AGENCY: Fish and Wildlife Service, Interior.
ACTION: Notice of 12-month petition finding.
SUMMARY: We, the U.S. Fish and Wildlife Service (Service), announce a 12-month finding on a petition to list the basalt juga (Juganew species(n. sp.) 2), canary duskysnail (Colligyrus convexus), cinnamon juga (Jugan. sp. 3), Columbia duskysnail (Colligyrusn. sp. 1), Fredenburg pebblesnail (Fluminicolan. sp.11), Goose Valley pebblesnail (Fluminicola anserinus), Hat Creek pebblesnail (Fluminicola umbilicatus), Klamath Rim pebblesnail (Fluminicolan. sp.3), knobby rams-horn (Vorticifexn. sp. 1), masked duskysnail (Colligyrusn. sp.2), nugget pebblesnail (Fluminicola seminalis), Potem Creek pebblesnail (Fluminicola potemicus), Shasta pebblesnail (Fluminicola multifarius), and tall pebblesnail (Fluminicolan. sp.2) as endangered or threatened, and to designate critical habitat, under the Endangered Species Act of 1973, as amended (Act). The Fredenburg pebblesnail and the Klamath Rim pebblesnail were referred to in the petition and in our 90-day finding (76 FR 61826) as the nerite pebblesnail and the diminutive pebblesnail, respectively (seeClarification Regarding Common Names for Two Petitioned Aquatic Mollusks,below). After review of the best available scientific and commercial information, we find that listing the basalt juga, cinnamon juga, Columbia duskysnail, Fredenburg pebblesnail, Klamath Rim pebblesnail, knobby rams-horn, masked duskysnail, and tall pebblesnail is not warranted at this time because these snails do not constitute listable entities under the Act (see Listable Entity Evaluation, below). We ask the public to submit to us new information that becomes available concerning the taxonomic status of these mollusks. We find that listing the canary duskysnail, Goose Valley pebblesnail, Hat Creek pebblesnail, nugget pebblesnail, Potem Creek pebblesnail, and Shasta pebblesnail is not warranted at this time. We ask the public to submit to us new information that becomes available concerning threats to these mollusks.
DATES: The finding announced in this document was made on September 18, 2012.
ADDRESSES: This finding is available on the Internet athttp://www.regulations.govat Docket Number FWS-R8-ES-2011-0076. Supporting documentation we used in preparing this finding is available for public inspection, by appointment, during normal business hours at the U.S. Fish and Wildlife Service, Sacramento Fish and Wildlife Office, 2800 Cottage Way, Room W-2605, Sacramento, California 95825. Please submit any new information, materials, comments, or questions concerning this finding to the above address.
FOR FURTHER INFORMATION CONTACT: Listing Coordinator, U.S. Fish and Wildlife Service, Sacramento Fish and Wildlife Office (seeADDRESSES); by telephone at 916-414-6600; or by facsimile at 916-414-6712mailto:. If you use a telecommunications device for the deaf (TDD), please call the Federal Information Relay Service (FIRS) at 800-877-8339.
SUPPLEMENTARY INFORMATION:

List of Acronyms

To assist the reader, the following is a partial list of acronyms that are used in this document.

ACS = Aquatic Conservation Strategy ANSTF = Aquatic Nuisance Species Task Force BNSF = Burlington Northern and Santa Fe CAL FIRE = California Department of Forestry and Fire Protection CBD = Center for Biological Diversity CDFG = California Department of Fish and Game CDPR = California Department of Parks and Recreation CNDDB = California Natural Diversity Database DPS = distinct population segment FERC = Federal Energy Regulatory Commission FPA = Forest Practice Act FRRCD = Fall River Resource Conservation District IPCC = Intergovernmental Panel on Climate Change NBII = National Biological Information Infrastructure NWP = Northwest Forest Plan OHV = off-highway vehicle ORNHIC = Oregon Natural Heritage and Information Center PDA = Public Domain Allotment PGE = Pacific Gas and Electric Company RCAs = Riparian Conservation Areas SHU = Shasta-Trinity Unit SMP = Survey and Manage Program SNFPA = Sierra Nevada Forest Plan Amendment SPR = significant portion of the range SWRCB = State Water Resources Control Board THP = Timber Harvest Plan Background

Section 4(b)(3)(B) of the Act (16 U.S.C. 1531et seq.) requires that, for any petition to revise the Federal Lists of Threatened and Endangered Wildlife and Plants that contains substantial scientific or commercial information that listing a species may be warranted, we make a finding within 12 months of the date of receipt of the petition. In this finding, we will determine that the petitioned action is: (1) Not warranted; (2) warranted; or (3) warranted, but the immediate proposal of a regulation implementing the petitioned action is precluded by other pending proposals to determine whether species are endangered or threatened, and expeditious progress is being made to add or remove qualified species from the Federal Lists of Endangered and Threatened Wildlife and Plants. Section 4(b)(3)(C) of the Act requires that we treat a petition for which the requested action is found to be warranted but precluded as though resubmitted on the date of such finding, that is, requiring a subsequent finding to be made within 12 months. We must publish these 12-month findings in theFederal Register.

Previous Federal Actions

On March 17, 2008, we received a petition dated March 13, 2008, from five conservation organizations: The Center for Biological Diversity (CBD), Conservation Northwest, the Environmental Protection Information Center, the Klamath-Siskiyou Wildlands Center, and Oregon Wild. The petition asked us to list 32 species and subspecies of snails and slugs (mollusks) in the Pacific Northwest as threatened or endangered under the Act. Additionally, the petition requested that we designate critical habitat concurrent with listing. The petition clearly identified itself as a petition and included identification information regarding the petitioners, as required by title 50 of the Code of Federal Regulations (CFR) in 424.14(a). The petition included the 14 aquatic mollusk species addressed in this finding, and provided supporting information regarding the species' taxonomy and ecology, range, present status, and actual and potential causes of decline.

In a June 27, 2008, letter to the petitioners, we responded that we had reviewed the information presented in the petition and determined that issuing an emergency regulation temporarilylisting the species as per section 4(b)(7) of the Act was not warranted. We also stated that we could not address their petition at that time due to court orders and judicially approved settlement agreements for other listing and critical habitat determinations under the Act that required nearly all of our listing and critical habitat funding for fiscal years 2008 and 2009. We indicated that we anticipated making an initial finding on their petition in fiscal year 2010.

On April 13, 2009, we received a signed email from CBD providing updated taxonomic information regarding some of the 32 petitioned mollusk species (Curry 2009, pp. 1-2). The email indicated that two of the species had been formally described, two others had been combined into a single species that had been formally described, and three additional petitioned species had been combined into a single species that had been formally described. The email provided a citation to the article making the taxonomic changes, and asked us to consider the revised species for listing as endangered or threatened under the Act. We treated this email message as an amendment to the original petition. Therefore, the amended petition asked us to list 29 species and subspecies of mollusks, including the 14 aquatic species addressed here.

We addressed the petition as funding permitted beginning in late 2009, and published a 90-day finding on October 5, 2011 (76 FR 61826). We found that substantial scientific and commercial information had been presented in the petition and existed in our files to indicate listing may be warranted for 26 of the 29 petitioned mollusks. Fourteen of those 26 mollusks are aquatic and 12 are terrestrial. We have initiated a status review of the 14 aquatic mollusks, and present the results here. We intend to review the status of the remaining 12 terrestrial mollusks in fiscal year 2013. This notice constitutes our 12-month finding on the June 27, 2008, petition (as amended on April 13, 2009) to list 14 aquatic mollusks as endangered or threatened.

Clarification Regarding Common Names for Two Petitioned Aquatic Mollusks

The mollusks petitioned for listing included the “diminutive pebblesnail (Fluminicolan. sp. 3)” (CBDet al.2008, pp. 9, 44) and the “nerite pebblesnail (Fluminicolan. sp. 11)” (CBDet al.2008, pp. 9, 46). In our 90-day finding, which was limited in scope to information provided by the petition and available in our files, we noted that these mollusks were sometimes referred to by cited sources other than the petition as the Klamath Rim pebblesnail and the Fredenburg pebblesnail, respectively (76 FR 61836, 61843). Information that we reviewed for this status review indicates that the only accepted common names for these mollusks are the Klamath Rim pebblesnail and the Fredenburg pebblesnail. The only sources that refer to these two mollusks by the common names used in the petition are the Oregon Natural Heritage and Information Center (ORNHIC) (2004d, p. 1) for the diminutive pebblesnail, and ORNHIC (2004j, p. 1) for the nerite pebblesnail. However, these must be incorrect rather than simply alternate common names because Frest and Johannes (the original discoverers of these snails) refer to all four named mollusks as separate species (Frest and Johannes 1993, pp. 46, 47, 49; Frest and Johannes 2000, pp. 181, 264, 267, 273).

They note that the Klamath Rim and Fredenburg pebblesnails are protected under the Survey and Manage Program (SMP) of the Northwest Forest Plan (NWFP) (seeGenerally Applicable Federal Regulatory Mechanisms,below), whereas the diminutive and nerite pebblesnails “should be” included in that program (Frest and Johannes 2000, pp. 264, 265, 268, 274). The petition only included mollusks that had been protected under the SMP (CBDet al.2008, p. 12). An Environmental Impact Statement (EIS) on which we relied in our 90-day finding for information regarding occupied locations of various mollusks, identifies all the petitioned mollusks by their scientific names alone, without providing common names (for example, U.S. Department of Agriculture (USDA) and U.S. Department of the Interior (USDI) 2007, pp. 92, 251).

In the case of these two mollusks, the “scientific names” were provisional and subject to change in different documents (Frest and Johannes 1993, pp. 46, 49; Frest and Johannes 2000, pp. 264, 273) (see Listable Entity Evaluation, below). However, we have subsequently obtained the survey protocol for aquatic mollusk species under the SMP, and that document identifiesFluminicolan. sp. 3 and n. sp. 11 as the Klamath Rim and Fredenburg pebblesnails, respectively (Furnishet al.1997, p. 29). It does not mention the diminutive or nerite pebblesnails, presumably because they were not protected by the SMP. Accordingly, in this document we will refer to the petitioned molluskFluminicolan. sp. 3 as the Klamath Rim pebblesnail and to the petitioned molluskFluminicolan. sp. 11 as the Fredenburg pebblesnail, rather than as the diminutive and nerite pebblesnails, respectively.

Listable Entity Evaluation

Section 3(16) of the Act defines the term “species” to include “any subspecies of fish or wildlife or plants, and any distinct population segment (DPS) of any species of vertebrate fish or wildlife which interbreeds when mature.” Taxonomic groups or entities that meet the Act's definition of a “species” can be considered for listing under the Act and are, therefore, referred to as “listable entities.” Listable entities can then be listed if they are determined to meet the definition of either an endangered or threatened species.

Of the 14 aquatic mollusks considered in this review, 8 have not been formally described as species or subspecies in a peer-reviewed journal, or in any other source commonly accepted by the scientific community. This is why they have provisional scientific names, including “new species” (or “n. sp.”) and a number, rather than accepted species names. Formal peer-reviewed description, with its opportunities for further review and comment, is the process by which proposed new species and subspecies become generally recognized or rejected by the taxonomic community. We must therefore evaluate whether the best available scientific and commercial information indicates that these eight mollusks constitute valid species, despite their lack of formal descriptions, for the purpose of determining whether the mollusks in question constitute listable entities (16 U.S.C. 1533(b)(3)(A) and (B)). It is rare for us to list entities that have not been formally described, but we have occasionally done so in the past. Examples include two fish: The Hutton tui chub (Gila bicolorssp.) and Foskett speckled dace (Rhinichthys osculusssp.) (50 FR 12302; March 28, 1985). In those instances, there was general agreement among biologists familiar with these fish that they constituted listable subspecies, and formal descriptions of the subspecies were in preparation. Additionally, if our determination of the status of these fish as valid subspecies had been incorrect, the fish would still likely have constituted distinct vertebrate population segments, and thus qualified as listable entities under section 3(16) of the Act. Mollusk populations are not listable entities, unless they also constitute valid species or subspecies, because the provision in section 3(16) allowing DPSs to be listed only applies to vertebrates (16 U.S.C. 1532(16)).

The eight aquatic mollusks reviewed here that have not been formally described are: Basalt juga, cinnamon juga, Columbia duskysnail, Fredenburg pebblesnail, Klamath Rim pebblesnail, knobby rams-horn, masked duskysnail, and tall pebblesnail. Table 1 below summarizes basic taxonomic and biological information for these purported species.

Table 1—Basic Biology of Mollusks Lacking Formal Descriptions Common name Description Habitat Known sites Basalt juga Shell about 22 by 10 mm *; color bands of yellow, brown, pink, white, or tan (Frest and Johannes 1999, p. 85) Small, gravelly springs with unpolluted water (Frest and Johannes 1995a, p. 179) 31 sites in Hood River, Sherman, and Wasco Counties, OR; and Klickitat and Skamania Counties, WA (BLM 2011, entire). Cinnamon juga Shell about 15 by 8 mm; cinnamon red but can appear black in the field (Frest and Johannes 1999, p. 89) Large cold springs and spring runs, with sand-cobble substrate or exposed basalt bedrock (Frest and Johannes 1999, p. 90) 8 sites in the Shasta Springs complex, upper Sacramento River, Siskiyou County, CA (Frest and Johannes 1999, p. 90). Columbia duskysnail Shell about 1.7 by 1.4 mm; translucent, off-white, often with rust to black coating (Frest and Johannes 1999, p. 69) Cold, shallow, well-oxygenated, slow-flowing springs and outflows with soft substrates. (Duncan 2005b, p. 10) 64 sites in Clackamas, Wasco, Hood River, and Multnomah Counties, OR; and Skamania County, WA (USDA and USDI 2007, p. 93). Fredenburg pebblesnail Shell about 3 by 2.5 mm; white with greenish-yellow outer layer; white, sickle-shaped penis. (Frest and Johannes 1999, p. 29) Small, shallow, cold spring runs with cobbled substrate (Frest and Johannes 1999, p. 30) 19 sites in Jackson County, OR. (Frest and Johannes 1999, p. 30; USDA and USDI 2007, p. 92). Klamath Rim pebblesnail Shell about 2 by 2 mm; white with greenish-yellow outer layer; sickle-shaped penis (Frest and Johannes 1999, p. 25) Shady areas in small, cold, shallow spring runs with gravel-cobble substrates and no large water plants (Frest and Johannes 1999, p. 26) 6 sites in southern OR and possibly northern CA (USDA and USDI 2007, pp. 92, 251). Knobby rams-horn Shell about 6 by 6 mm; reddish-brown outer layer, keeled with ribs and protuberances (Frest and Johannes 1995b, p. 57; Frest and Johannes 1999, p. 98) Rocky substrates in cold, clear water with high dissolved oxygen levels (Frest and Johannes 1999, p. 99) 2 sites in Shasta County, CA (USDA and USDI 2007, pp. 94, 268). Masked duskysnail Shell described as up to 2 mm long (Frest and Johannes 1995a, p. 185) or as 3 to 5 mm long (Frest and Johannes 1999, p. 73); mask of black pigment on neck and around eyes (Frest and Johannes 1999, p. 73) Cool-water kettle lakes with oxygenated mud substrates and aquatic plant growth (Duncan 2005e, p. 3) 3 to 4 sites at two lakes: Curlew Lake, Ferry County, WA, and Fish Lake, Chelan County, WA (Duncan 2005e, p. 3; USDA and USDI 2007, p. 94). Some indications of possible additional sites in ID and OR (ORNHIC 2004u, p. 1). Tall pebblesnail Shell about 4.5 by 3 mm; conical, white with green outer layer; black body except for white, flanged penis (Frest and Johannes 1999, p. 21) Very cold water and cobbled substrate (Duncan 2005b, p. 9) 1 site at Harriman Spring, Klamath County, OR (Duncan 2005b, p. 9; USDA and USDI 2007, p. 92). * mm = millimeter.

None of these eight aquatic mollusks are included in databases of recognized mollusk species, such as the Integrated Taxonomic Information System (ITIS) (2010), or Turgeonet al.(1998). All eight mollusks were first proposed as new species in an unpublished consultation report produced in 1993 (Frest and Johannes 1993, pp. 46, 49, 50, 59, 62, 67). These eight mollusks have been addressed in several subsequent documents (Frest and Johannes 1999, pp. 21-26, 29-30, 69-76, 85-90, 98-101; Furnish and Monthey 1999, Sections 2, 4, 5, entire; Frest and Johannes 2000, pp. 181, 264, 273, 274; ORNHIC 2004a, entire; ORNHIC 2004d, entire; ORNHIC 2004j, entire; ORNHIC 2004r, entire; ORNHIC 2004s, entire; ORNHIC 2004t, entire; ORNHIC 2004u, entire; ORNHIC 2004v, entire; Duncan 2005b, entire; Duncan 2005e, entire; USDA and USDI 2007, pp. 92-94, 250-252, 257-259, 268-269), but none of those documents provide peer-reviewed evidentiary support of the mollusks' taxonomic distinctness. Although the eight mollusks have been treated by the U.S. Forest Service (USFS) and Bureau of Land Management (BLM) as distinct entities under the SMP of the Northwest Forest Plan (see Factor D, below), that program is not specifically restricted to species or subspecies, as is the Act when applied to invertebrates (16 U.S.C. 1532 (16)).

The unpublished descriptions of these eight mollusks are all primarily based on shell characteristics, with occasional mention of certain characters of the animals themselves (such as color). Snail shell characteristics in general can vary due to environmental influences including elevation, calcium content of the surrounding water, and population density (Minton and Lydeard 2003, p. 76; Chak 2007, p. 3). The informal descriptions lack genetic data, data regarding microscopic anatomical features such as the radula (tongue), and photographs or drawings of anatomical features other than the shell. Such data are often highly distinctive, and are of key importance in formal descriptions (for example, Hershleret al.2003, pp. 278-282; Hershleret al.2007, pp. 407-419).

At the time the petition to list these aquatic mollusks was first submitted, only one of the petitioned mollusks (the nugget pebblesnail) had been formally described (CBDet al.2008, p. 9). Since then, an additional five mollusks have been formally described and thereby established in the scientific community as valid species. These are the canary duskysnail, Goose Valley pebblesnail, Hat Creek pebblesnail, Potem Creek pebblesnail, and Shasta pebblesnail (Hershleret al.2003, p. 278; Hershleret al.2007, pp. 407, 409, 412, 415). For three of these recently described species (the canary duskysnail, Goose Valley pebblesnail, and Potem Creek pebblesnail), the formal descriptionssimply confirm the informal species designations under which they had been petitioned. However, the formal description of the Hat Creek pebblesnail combined into one species two of the petitioned mollusks that had previously been informally described as separate species (the umbilicate pebblesnail (Fluminicolan. sp. 19) and the Lost Creek pebblesnail (Fluminicolan. sp. 20). Similarly, the formal description of the Shasta pebblesnail combined four mollusks that had previously been informally described as separate species (Hershleret al.2007, p. 419)). Three of those had been petitioned for listing (CBDet al.2008, p. 9): the flat-top, Shasta Springs, and disjunct pebblesnails (identified asFluminicolan. sp. 3, 4, and 5 in Frest and Johannes 1995b, pp. 43, 44; but asFluminicolan. sp. 15, 16, and 17 in Frest and Johannes 1999, pp. 39, 43, 47 and in CBDet al.2008, p. 9). The fourth, the Sacramento pebblesnail (Fluminicolan. sp. 1) (Frest and Johannes 1995b, p. 42) had not been petitioned for listing and was not protected by the SMP (USDA and USDI 2007, pp. 92-94). In describing the Shasta pebblesnail, the authors noted the “[m]arked shell variation” of the species (Hershler et al.2007, p. 419).

The primary reason for combining multiple informally described mollusks in the formal descriptions of the Hat Creek and Shasta pebblesnails was that new genetic comparisons had shown those informally described mollusks were not genetically divergent or phylogenetically independent (Hershleret al.2007, p. 383). Such genetic comparisons have not yet been published for the remaining undescribed mollusks. This suggests the remaining but undescribed mollusks may also be determined by future taxonomic analyses to represent populations of larger-ranging species or subspecies. New taxonomic analyses are currently being conducted for a large number of provisionally identified species in theFluminicolagenus (Johannes 2011, p. 1). Additionally, the establishment of the Shasta pebblesnail as a single species, despite the marked differences in shell morphology among its various populations, indicates that shell morphology is a relatively poor indicator of species status for at least some of these mollusks.

Accordingly, we conclude that the eight mollusks that have not been formally described (as listed in Table 1, above) cannot be considered to be listable entities under the Act at this time, and, therefore, we will not further evaluate the status of these entities. These include the Basalt juga, cinnamon juga, Columbia duskysnail, Fredenburg pebblesnail, Klamath Rim pebblesnail, knobby rams-horn, masked duskysnail, and tall pebblesnail. We, therefore, restrict the remainder of our listing status review to the six mollusks constituting listable entities under the Act. These are the canary duskysnail, the Goose Valley pebblesnail, the Hat Creek pebblesnail, the nugget pebblesnail, the Potem Creek pebblesnail, and the Shasta pebblesnail.

Generally Applicable Federal Regulatory Mechanisms The Northwest Forest Plan

The Northwest Forest Plan (NWFP) is a set of amendments to the resource management plans for USFS and BLM lands within the range of the northern spotted owl (Strix occidentalis caurina) in western Washington, Oregon, and northwestern California (referred to below as NWFP lands) (USDA and USDI 1994a, pp. 11, 12). The NWFP was established to protect species commonly occurring in late-successional and old-growth forests, while also allowing for sustainable timber production (USDA and USDI 1994a, p. 3). The NWFP established several categories of land allocations and, with minor exceptions, restricted timber production to those areas designated as Matrix Lands (16 percent of the total) and to certain Adaptive Management Areas (6 percent of the total) (USDA and USDI 1994a, pp. 6, 7). The NWFP includes two subprograms designed to provide additional protections to specific resources on NWFP lands. The first subprogram is the Aquatic Conservation Strategy (ACS), which protects aquatic and riparian habitat. The second subprogram is the SMP, which protects numerous rare species associated with late-successional or old-growth forests that are not adequately protected by other provisions of the NWFP (USDA and USDI 1994a, pp. 9, 10; Olsonet al.2007, pp. 1, 2). The ACS and SMP are particularly applicable, in varying degrees, to the six listable aquatic mollusks considered here, and are discussed in more detail below.

The Aquatic Conservation Strategy

The ACS was established to protect and restore aquatic ecosystems on NWFP lands (USDA and USDI 1994b, p. B-11; Reeveset al.2006, p. 320). The ACS includes four components: Riparian reserves, key watersheds, watershed analysis, and watershed restoration (USDA and USDI 1994a, pp. 9, 10). Of these, riparian reserves are the most significant conservation tool for the aquatic mollusks considered here. Riparian reserves include all aquatic habitat (perennial and seasonal streams, lakes, ponds, and wetlands) on NWFP lands. Riparian reserves are managed to maintain and restore water quality, aquatic ecosystem physical integrity, instream flows, habitat connectivity, and other natural features of the protected riparian and aquatic habitat (USDA and USDI 1994b, pp. B-11, B-13). Activities with the potential to negatively affect natural features, such as logging, road construction and maintenance, grazing, recreation, mineral management, and fire management are closely regulated within the reserves (USDA and USDI 1994a, p. 9; USDA and USDI 1994b, pp. C-31—C-38).

Riparian reserves incorporate buffers of 100 to 300 feet (ft) (30.5 to 91.4 meters (m)) around these aquatic features (except for wetlands of less than 1 acre (ac) (0.4 hectares (ha)), which have buffers that extend to the limit of the associated riparian vegetation). The six listable aquatic mollusks considered in this review all occupy springs (including those forming lakes or ponds) and perennial streams, sometimes fish-bearing and sometimes not (a stream is considered fish bearing if it supports any species of fish for any duration of time) (USDA and USDI 1994b, p. B-14). When any of these six mollusks are on NWFP lands in lakes, ponds, or fish-bearing streams, they are protected by buffers extending outward 300 ft (91.4 m) from the streambanks, to the limit of riparian vegetation or to a distance equal to the height of two site-potential trees, whichever is greater (USDA and USDI 1994a, p. 9). “Site-potential tree height” refers to the expected height attainable by a mature conifer growing in the area (Kier Associates 2011a, p. 2). Average site-potential tree height for much of the Pacific Northwest is about 170 ft (51.8 m). When present in non-fish-bearing streams on NWFP lands, the six mollusks are protected by buffers of 150 ft (45.7 m) or equal to the height of one site-potential tree, whichever is greater. These boundaries may be modified based on subsequent watershed analysis (USDA and USDI 1994a, p. 10; USDA and USDI 1994b, p. B-13)).

The second component of the ACS, key watersheds, establishes specific watersheds to be given the highest priority in watershed restoration efforts (USDA and USDI 1994b, p. B-19). None of the key watersheds identified under the ACS are in the known current range of, or upstream from, any of the six aquatic mollusks that qualify as listable entities (REO 2006, p. 5). Accordingly, the key watersheds provision of the ACS does not affect the conservation of thosesix mollusks, except if new locations of those species are identified within key watersheds in the future.

The third component of the ACS, watershed analysis, is a systematic procedure to collect information on and characterize watersheds on NWFP lands (USDA and USDI 1994b, pp. B-20—B-31). Watershed analysis must be conducted in key watersheds and roadless areas prior to management activities, in riparian reserves prior to changing reserve widths, and in any watershed prior to restoration efforts. Watershed analysis is recommended for all watersheds, and has been conducted on an ongoing basis since its inclusion in the NWFP (USDA 2009, p. 1). Analyses have been conducted for portions of the upper Sacramento River and lower McCloud River watersheds, which support occupied sites of the Shasta pebblesnail and nugget pebblesnail, respectively.

The final component of the ACS, watershed restoration, focuses primarily on restoring watershed aquatic habitat through the prevention of road-related runoff, restoration of riparian vegetation, and restoration of instream habitat complexity (USDA and USDI 1994b, p. B-31). The Shasta-Trinity and Lassen National Forests are currently planning or implementing several such watershed restoration projects (USDA 2012a, pp. 4, 5; USDA 2012b, pp. 3, 5), although none of the currently active projects involve locations near sites occupied by the mollusks addressed in this status review at the present time.

The Survey and Manage Program

The SMP, like the ACS, was established under the NWFP and is particularly applicable, in varying degrees, to the six listable aquatic mollusks considered here. The six mollusks were protected under the SMP (when on Federal lands subject to the NWFP), but the SMP program was discontinued in 2007 (USDA and USDI 2007, pp. xii, xiii; CBDet al.2008, p. 5). The SMP was subsequently reinstated in accordance with a court-approved settlement agreement in 2011 (Conservation Northwestv.Sherman 2011,C08-1067-JCC, p. 2), and is being implemented in accordance with the 2001 Record of Decision. All of the aquatic mollusks petitioned in 2008 (both formally described and otherwise) are protected where they occur on NWFP lands (Conservation Northwestv.Sherman 2011,C08-1067-JCC, Document 81-2, pp. 6, 7). Refinements to the SMP in 2001 established six species categories with differing mitigation requirements based on the species' conservation status and on the practicality of conducting predisturbance surveys (surveys conducted prior to habitat-disturbing projects) (Molinaet al.2006, p. 311, 312). Rare species for which predisturbance surveys are practical are in Category A. Thirteen of the 14 petitioned aquatic mollusks fall into this category, including all six of the listable mollusks (USDA and USDI 2007, pp. 92-94). The one exception among the petitioned aquatic mollusks is the knobby rams-horn (see Table 1, above), which is in Category E (rare, practicality of predisturbance surveys undetermined) (Molinaet al.2006, p. 312; USDA and USDI 2007, p. 94).

For Category A species, the SMP requires predisturbance, strategic surveys (conducted in areas not currently under consideration for habitat-disturbing projects), management of all known sites to support species persistence, and annual species reviews (Molinaet al.2006, p. 312; Olsonet al.2007, abstract). Numerous such surveys and several annual reviews have been completed (Molinaet al.2006, pp. 312-315; USDA and USDI 2001, entire; USDA and USDI 2002, entire; USDA and USDI 2003, entire). The process of continually collecting information through surveys, and of summarizing and updating the information in annual reviews, produces an adaptive management approach to guide conservation and mitigation measures for rare species associated with late-successional or old-growth forests (Olsonet al.2007, p. 2).

Summary of Procedures for Determining the Listing Status of Species Review of Status Based on Five Factors

Section 4 of the Act (16 U.S.C. 1533) and implementing regulations (50 CFR part 424) set forth procedures for adding species to, removing species from, or reclassifying species on the Federal Lists of Endangered and Threatened Wildlife and Plants. Under section 4(a)(1) of the Act, a species may be determined to be endangered or threatened based on any of the following five factors:

(A) The present or threatened destruction, modification, or curtailment of its habitat or range;

(B) Overutilization for commercial, recreational, scientific, or educational purposes;

(C) Disease or predation;

(D) The inadequacy of existing regulatory mechanisms; or

(E) Other natural or manmade factors affecting its continued existence.

In making these findings, we discuss information below pertaining to each species in relation to the five factors provided in section 4(a)(1) of the Act. In considering what factors might constitute threats to a species, we must look beyond the simple exposure of the species to a particular factor. Instead we must evaluate whether the species may respond to the factor in a way that causes actual impacts to the species. If there is exposure to a factor and the species responds negatively, the factor may be a threat and, during the status review, we attempt to determine how significant a threat it is. The threat is significant if it drives or contributes to the risk of extinction of the species such that the species warrants listing as endangered or threatened as those terms are defined by the Act. However, the identification of factors that could impact a species negatively may not be sufficient to compel a finding that the species warrants listing. The information must include evidence sufficient to suggest that the potential threat has the capacity (is of sufficient magnitude and extent) to affect the species' status such that it meets the definition of endangered or threatened under the Act.

Distinct Population Segments

After considering the five factors, we assess whether each species is endangered or threatened throughout all of its range. Generally, we next consider in our findings whether a DPS or any significant portion of the species' range meets the definition of endangered or is likely to become endangered in the foreseeable future (threatened).The inclusion of DPSs in the definition of species under paragraph 3(16) of the Act only applies to vertebrate fish or wildlife. Therefore, our Policy Regarding the Recognition of Distinct Vertebrate Population Segments Under the Endangered Species Act (DPS Policy) (61 FR 4722; February 7, 1996) is not applicable to mollusks and no population segments under review could qualify as a DPS under the Act. Although our DPS Policy is not applicable to mollusks, we do determine in our findings whether a mollusk species is endangered or threatened in a significant portion of its range.

Significant Portion of the Range

Under the Act and our implementing regulations, a species may warrant listing if it is endangered or threatened throughout all or a significant portion of its range. The Act defines “endangered species” as any species which is “in danger of extinction throughout all or a significant portion of its range,” and “threatened species” as any species which is “likely to become anendangered species within the foreseeable future throughout all or a significant portion of its range.” The definition of “species” is also relevant to this discussion. The Act defines “species” as follows: “The term `species' includes any subspecies of fish or wildlife or plants, and any DPS of any species of vertebrate fish or wildlife which interbreeds when mature.” The phrase “significant portion of its range” (SPR) is not defined by the statute, and we have never addressed in our regulations: (1) The consequences of a determination that a species is either endangered or likely to become so throughout a significant portion of its range, but not throughout all of its range; or (2) what qualifies a portion of a range as “significant.”

Two recent district court decisions have addressed whether the SPR language allows the Service to list or protect less than all members of a defined “species”:Defenders of Wildlifev.Salazar,729 F. Supp. 2d 1207 (D. Mont. 2010), concerning the Service's delisting of the Northern Rocky Mountain gray wolf (74 FR 15123, April 2, 2009); andWildEarth Guardiansv.Salazar,2010 U.S. Dist. LEXIS 105253 (D. Ariz. September 30, 2010), concerning the Service's 2008 finding on a petition to list the Gunnison's prairie dog (73 FR 6660, February 5, 2008). The Service had asserted in both of these determinations that it had authority, in effect, to protect only some members of a “species,” as defined by the Act (i.e., species, subspecies, or DPS), under the Act. Both courts ruled that the determinations were arbitrary and capricious on the grounds that this approach violated the plain and unambiguous language of the Act. The courts concluded that reading the SPR language to allow protecting only a portion of a species' range is inconsistent with the Act's definition of “species.” The courts concluded that once a determination is made that a species (i.e., species, subspecies, or DPS) meets the definition of “endangered species” or “threatened species,” it must be placed on the list in its entirety and the Act's protections applied consistently to all members of that species (subject to modification of protections through special rules under sections 4(d) and 10(j) of the Act).

Consistent with that interpretation, and for the purposes of this finding, we interpret the phrase “significant portion of its range” in the Act's definitions of “endangered species” and “threatened species” to provide an independent basis for listing; thus there are two situations (or factual bases) under which a species would qualify for listing: a species may be endangered or threatened throughout all of its range; or a species may be endangered or threatened in only a significant portion of its range. If a species is in danger of extinction throughout a significant portion of its range, the species is an “endangered species.” The same analysis applies to “threatened species.” Based on this interpretation and supported by existing case law, the consequence of finding that a species is endangered or threatened in only a significant portion of its range is that the entire species shall be listed as endangered or threatened, respectively, and the Act's protections shall be applied across the species' entire range.

We conclude, for the purposes of this finding, that interpreting the significant portion of its range phrase as providing an independent basis for listing is the best interpretation of the Act because it is consistent with the purposes and the plain meaning of the key definitions of the Act; it does not conflict with established past agency practice (i.e., prior to the 2007 Solicitor's Opinion), as no consistent, long-term agency practice has been established; and it is consistent with the judicial opinions that have most closely examined this issue. Having concluded that the phrase “significant portion of its range” provides an independent basis for listing and protecting the entire species, we next turn to the meaning of “significant” to determine the threshold for when such an independent basis for listing exists.

Although there are potentially many ways to determine whether a portion of a species' range is “significant,” we conclude, for the purposes of this finding, that the significance of the portion of the range should be determined based on its biological contribution to the conservation of the species. For this reason, we describe the threshold for “significant” in terms of an increase in the risk of extinction for the species. We conclude that a biologically based definition of “significant” best conforms to the purposes of the Act, is consistent with judicial interpretations, and best ensures species' conservation. Thus, for the purposes of this finding, and as explained further below, a portion of the range of a species is “significant” if its contribution to the viability of the species is so important that without that portion, the species would be in danger of extinction.

We evaluate biological significance based on the principles of conservation biology using the concepts of redundancy, resiliency, and representation.Resiliencydescribes the characteristics of a species and its habitat that allow it to recover from periodic disturbance.Redundancy(having multiple populations distributed across the landscape) may be needed to provide a margin of safety for the species to withstand catastrophic events.Representation(the range of variation found in a species) ensures that the species' adaptive capabilities are conserved. Redundancy, resiliency, and representation are not independent of each other, and some characteristic of a species or area may contribute to all three. For example, distribution across a wide variety of habitat types is an indicator of representation, but it may also indicate a broad geographic distribution contributing to redundancy (decreasing the chance that any one event affects the entire species), and the likelihood that some habitat types are less susceptible to certain threats, contributing to resiliency (the ability of the species to recover from disturbance). None of these concepts is intended to be mutually exclusive, and a portion of a species' range may be determined to be “significant” due to its contributions under any one or more of these concepts.

For the purposes of this finding, we determine if a portion's biological contribution is so important that the portion qualifies as “significant” by asking whetherwithout that portion,the representation, redundancy, or resiliency of the species would be so impaired that the species would have an increased vulnerability to threats to the point that the overall species would be in danger of extinction (i.e., would be “endangered”). Conversely, we would not consider the portion of the range at issue to be “significant” if there is sufficient resiliency, redundancy, and representation elsewhere in the species' range that the species would not be in danger of extinction throughout its range if the population in that portion of the range in question became extirpated (extinct locally).

We recognize that this definition of “significant” (a portion of the range of a species is “significant” if its contribution to the viability of the species is so important that, without that portion, the species would be in danger of extinction) establishes a threshold that is relatively high. On the one hand, given that the consequences of finding a species to be endangered or threatened in a significant portion of its range would be listing the species throughout its entire range, it is important to use a threshold for “significant” that is robust. It would not be meaningful or appropriate to establish a very low threshold wherebya portion of the range can be considered “significant” even if only a negligible increase in extinction risk would result from its loss. Because nearly any portion of a species' range can be said to contribute some increment to a species' viability, use of such a low threshold would require us to impose restrictions and expend conservation resources disproportionately to conservation benefit: listing would be rangewide, even if only a portion of the range of minor conservation importance to the species is imperiled. On the other hand, it would be inappropriate to establish a threshold for “significant” that is too high. This would be the case if the standard were, for example, that a portion of the range can be considered “significant” only if threats in that portion result in the entire species being currently endangered or threatened. Such a high bar would not give the significant portion of its range phrase independent meaning, as the Ninth Circuit held inDefenders of Wildlifev.Norton,258 F.3d 1136 (9th Cir. 2001).

The definition of “significant” used in this finding carefully balances these concerns. By setting a relatively high threshold, we minimize the degree to which restrictions will be imposed or resources expended that do not contribute substantially to species conservation. But we have not set the threshold so high that the phrase “in a significant portion of its range” loses independent meaning. Specifically, we have not set the threshold as high as it was under the interpretation presented by the Service in theDefenderslitigation. Under that interpretation, the portion of the range would have to be so important that current imperilment there would mean that the species would becurrentlyimperiled everywhere. Under the definition of “significant” used in this finding, the portion of the range need not rise to such an exceptionally high level of biological significance. (We recognize that if the species is imperiled in a portion that rises to that level of biological significance, then we should conclude that the species is in fact imperiled throughout all of its range, and that we would not need to rely on the significant portion of its range language for such a listing.) Rather, under this interpretation we ask whether the species would be endangered everywhere without that portion,i.e.,if that portion were completely extirpated. In other words, the portion of the range need not be so important that even the species being in danger of extinction in that portion would be sufficient to cause the species in the remainder of the range to be endangered; rather, thecomplete extirpation(in a hypothetical future) of the species in that portion would be required to cause the species in the remainder of the range to be endangered.

The range of a species can theoretically be divided into portions in an infinite number of ways. However, there is no purpose to analyzing portions of the range that have no reasonable potential to be significant or to analyzing portions of the range in which there is no reasonable potential for the species to be endangered or threatened. To identify only those portions that warrant further consideration, we determine whether there is substantial information indicating that: (1) The portions may be “significant,”and(2) the species may be in danger of extinction there or likely to become so within the foreseeable future. Depending on the biology of the species, its range, and the threats it faces, it might be more efficient for us to address the significance question first or the status question first. Thus, if we determine that a portion of the range is not “significant,” we do not need to determine whether the species is endangered or threatened there; if we determine that the species is not endangered or threatened in a portion of its range, we do not need to determine if that portion is “significant.” In practice, a key part of the determination that a species is in danger of extinction in a significant portion of its range is whether the threats are geographically concentrated in some way. If the threats to the species are essentially uniform throughout its range, no portion is likely to warrant further consideration. Moreover, if any concentration of threats to the species occurs only in portions of the species' range that clearly would not meet the biologically based definition of “significant,” such portions will not warrant further consideration.

Evaluation of the Status of Each of the Six Mollusk Species That Are Listable Entities

For each of the six listable aquatic mollusk species considered, we provide a description of the species and its life history and habitat, an evaluation of listing factors, and our finding as to whether the petitioned action is warranted throughout its range. We then address whether the species may be considered endangered or threatened in any significant portion of its range.

Canary Duskysnail (Colligyrus convexus) Species Information for the Canary Duskysnail Taxonomy and Species Description

The canary duskysnail was formally named and described in 2003 (Hershleret al.2003, p. 278). Prior to that it was referred to as “Lyogyrusn. sp. 3” (Frest and Johannes 1999, pp. 77-78; Hershleret al.2003, p. 278; USDA and USDI 2007, pp. 93, 169), and also as “Lyogyrusn. sp. 1” (Frest and Johannes 1995b, p. 50). Although the canary duskysnail was considered to be in the Hydrobiidae family by earlier authors (Frest and Johannes 1995b, p. 50; Frest and Johannes 1999, p. 13), and was referred to as such in the listing petition (CBDet al.2008, p. 9), it was placed in the family Amnicolidae when it was formally described (Hershleret al.2003, p. 278). It is a small (1.4 to 1.9 millimeters (mm) 0.06 to 0.07 inches (in)), aquatic snail with a yellowish shell, sometimes with weakly striped markings on the whorls. It is distinguishable from the other two species in its genus by its smaller size, the highly convex whorls on the main part of its shell, and the waviness of the shell near the opening (Hershleret al.2003, p. 278).

Distribution

The canary duskysnail is known from a total of 21 sites in Shasta County, California, including 9 along the lower Pit River (California Natural Diversity Database (CNDDB) 2012, pp. 1-5; Johannes 2012a, pp. 2-7; Pacific Gas and Electric Company (PGE) 2011, pp. 26, 37; Johannes 2012b, p. 11; PGE 2012, p. 27). Of those 21 sites, 7 are on Federal land covered by the NWFP, 1 is on an Indian Public Domain Allotment (PDA), 3 are in State parks, and 10 are on privately owned lands. Repeat site monitoring at eight of those sites (see Factor A, below) shows large shifts in population density and in presence or absence of canary duskysnails at any given site. Site locations fall into three broad areas: The lower Pit River and nearby Burney Creek (11 sites), Hat Creek (2 sites), and the upper Fall and Tule River area (8 sites).

Habitat and Biology

The canary duskysnail typically occurs in shallow water on the undersides of boulders and cobbles in pond springs and wetted areas near streambeds (the hyporheic zone) (Hershleret al.2003, pp. 280, 284). It is most likely a grazer on perilithon, the community of small organisms such asalgae, protozoa, and bacteria growing underwater on stones (Frest and Johannes 1995b, p. 81; Furnish and Monthey 1999, Sect. 4, p. 9). It is most commonly found in areas lacking cover from aquatic plants, often in association with the Shasta crayfish (Pacifastacus fortis). It is found in, and is likely dependent on, water that is cold, clear, well-oxygenated, and unpolluted (Frest and Johannes 1995b, p. 3). It is often found in spring flows or in spring-influenced streams (Service 1998, p. 20; Frest and Johannes 1999, p. 78). The canary duskysnail is a short-lived species (1 to occasionally 2 years) that only reproduces once before dying (Frest and Johannes 1995b, p. 4; Furnish and Monthey 1999, Sect. 4, p. 7). Eggs are likely laid in the spring and hatch in 2 to 4 weeks (Furnish and Monthey 1999, Sect. 4, p. 7).

Five-Factor Evaluation of Threats for the Canary Duskysnail Factor A. The Present or Threatened Destruction, Modification, or Curtailment of Its Habitat or Range Impoundments

Nine of the 21 occupied sites are in or along the lower Pit River below Lake Britton (PGE 2011, pp. 26, 37; Johannes 2012b, p. 11; PGE 2012 p. 27). PGE maintains three dams in this area: Pit 3, 4, and 5 (PGE 2010, p. 5). Each dam sends water from its associated reservoir through tunnels to power-generating stations located just above the reservoirs of the next dam downstream. Flows in the natural river channel below each dam (referred to as the Pit 3, 4, and 5 reaches) have in the past consisted primarily of water from springs and minor tributaries emptying below each dam. In 2007, however, the Pit 3, 4, and 5 dams were issued a new operating license that required increased releases of surface water from the reservoirs into their associated reaches (PGE 2010, p. 2). These releases have the potential to negatively impact the canary duskysnail because reservoir surface water tends to be warmer than spring or creek water (Ellis 2012, p. 1). Because the dams initially lacked the infrastructure to release the required amounts of instream water, the required amounts were not achieved until 2011 (PGE 2012, p. 1). In accordance with a facilities modification plan, interim flow releases of approximately half the required amounts were authorized for 2008 through 2010 while the flow release structures of the dams were improved (PGE 2010, pp. 1, 2).

PGE was also required by the relicensing requirements to conduct mollusk surveys in 2009, in 2011-2015, in 2018, and every 4 years thereafter until the expiration of the license in 2043 (PGE 2012, p. 1). Following monitoring in 2009, PGE decided to monitor for mollusks in 2010 as well (PGE 2010, p. 54; PGE 2011, p. 1). Accordingly, we now have 3 years of survey data (2009-2011) for a total of 12 sites in the Pit River (four sites downstream of each dam) (PGE 2011, pp. 26, 37; PGE 2012, p. 27). The surveys found canary duskysnails at 8 of those 12 sites (as well as nugget pebblesnails at all 12 sites, as discussed below). A ninth site in the Pit River with canary duskysnails (as mentioned above) was not in a monitored location (Hershleret al.2003, p. 280; CNDDB 2012, p. 2; Johannes 2012a, p. 2).

Four of the eight monitored occupied sites are in the Pit 3 reach, which is the farthest upstream (PGE 2011, pp. 26, 37; PGE 2012, p. 27). During 2009, that reach also showed the lowest average water discharge rates, lowest average water temperatures, and produced the highest average densities of canary duskysnails, thus tending to support the idea that canary duskysnails benefit from lower discharge rates from the dams (PGE 2010, p. 35; PGE 2011, pp. 26, 37; PGE 2012, p. 27). However, as average water discharge rates increased in the Pit 3 reach from 150 cubic ft per second (cfs) in 2009 to 350 cfs in 2011, and as average water temperatures increased as well from approximately 60 to about 63 degrees Fahrenheit (°F) (15.4 to 17.2 degrees Celsius (°C)), canary duskysnail densities rose from 20 to 53 snails per square meter (16.7 to 44.3 snails per square yard) at one location (their highest density in the study), and dropped from 50 to 0 snails per square meter (41.8 to 0 snails per square yard) at another location. The populations thus showed strong fluctuations, with widely differing responses to increasing flows. Similarly, in the Pit 5 reach, 37 snails per square meter (30.9 snails per square yard) were found in 2011 (the year of highest flows) at a location that had supported no snails in the 2 previous years. All other occupied locations had comparatively low population densities, and only one of those showed a clear drop in population density over the 3-year monitoring period (from 4 to 0 snails per square meter (3.3 to 0 snails per square yard)). Therefore, we conclude there are no clear trends in observed survey data attributable to changes in flow releases from dams.

The only other occupied site potentially affected by an impoundment is at Baum Lake (CNDDB 2012, p. 4; Johannes 2012a, pp. 4, 5), a PGE-owned reservoir on Hat Creek, just north of the town of Cassel (Service 1998, pp. 20, 43). Abundant canary duskysnails were found at the site in 2001, under cobbles near the outflow of Crystal Lake, a spring-fed water body that abuts and empties into Baum Lake (CNDDB 2012, p. 4; Johannes 2012a, pp. 4, 5). Although the best available information does not indicate the fate of that population, its presence in 2001 and the abundant number of individual snails found at that time suggest the impoundment of Baum Lake does not constitute a threat. Three other occupied sites (identified in the source material as locations 102, 412, and 514) are located on the margins of spring-fed natural lakes in water bodies draining into the Fall River (Johannes 2012a pp. 3, 6), so the species is capable of surviving in slow-moving lake waters fed by nearby springs.

Water Quality

The Pit River is considered a water-quality limited segment for 198 kilometers (km) (123 miles (mi)) upstream of Shasta Lake; including the locations of all nine canary duskysnail sites known from the Pit River (State Water Resources Control Board (SWRCB) 2010a, p. 164). Nutrients from cattle defecation and fertilizers applied in the course of agriculture enter the Pit River, where they promote algal growth that decreases oxygen levels and increases water temperature. However, as discussed above with respect to impoundments, the only population trend data available for the canary duskysnail does not show clearly decreasing populations, despite any temperature increases or oxygen decreases that may be attributable to water quality.

PGE will continue to monitor mollusk populations annually as discussed above (PGE 2012, p. 1), so if impacts from Pit water quality or from the releases themselves do develop, they should be detected. The operating license for the dams includes an adaptive management plan for responding to negative impacts detected by the monitoring program (PGE 2008, pp. 3-6). The Service serves on the Technical Review Group which recommends specific adaptive management responses (PGE 2008, p. 2), and so will remain informed of the effectiveness of those responses. Seven of the nine occupied locations on the Pit River are on Federal land (either Shasta-Trinity National Forest or Lassen National Forest) within the area covered by the NWFP. Activities on those lands with the potential to affect water quality (or to affect the populations directly) would have to meet the requirements of the SMP and the ACS, as discussedabove. For instance, logging or road construction in the vicinity of the Pit River or its tributaries (on Federal lands within the NWFP area) would be subject to buffers for riparian reserves established under the ACS as well as predisturbance surveys and mitigation as required by the SMP.

There are no locations occupied by canary duskysnails on the Pit River upstream of the Pit 3 dam at Lake Britton. However, there are two locations each on Burney Creek and Hat Creek, which both flow into Lake Britton. The remaining eight canary duskysnail locations are in the Fall River drainage, generally at the headwater springs (Service 2012a, p. 1). Neither Burney Creek nor Hat Creek is considered water-quality limited (SWRCB 2010a, entire; SWRCB 2010b, entire; SWRCB 2010c, entire). However, the Fall River is affected by sedimentation extending far enough upstream to reach the southernmost of the eight sites in the drainage occupied by canary duskysnails (SWRCB 2010a, p. 148; SWRCB 2011, p. 2). The sedimentation was caused by historical land management activities, and is not likely to constitute a threat to the other sites (Fall River Resource Conservation District (FRRCD) 2005, pp. 1-3; SWRCB 2010a, p. 148).

A final area with impaired water quality is Eastman Lake, at the headwaters of the Little Tule River, a tributary of the Fall River (SWRCB 2010a, p. 148; SWRCB 2011, p. 1). One canary duskysnail site (514) is located at the lake, while two others (102, 263) are just upstream of the inlet (Johannes 2012a, pp. 3, 4, 6). At an average pH of 8.64, the lake water is slightly more alkaline than the established water quality objective range of 6.5 to 8.5 (SWRCB 2010d, pp. 6, 7). The reason for the increased alkalinity is unknown, as is the optimal pH range for the canary duskysnail. However, acidic waters (pH 5 and below) can interfere with shell production, so freshwater snails are generally found in waters that are at least somewhat alkaline (Wyoming Game and Fish Department (WGFD) 2005, p. 548).

Other Habitat-Related Impacts

Grazing, spring diversions, road construction, and railroad construction have all been mentioned as possible threats to the canary duskysnail (Furnish and Monthey 1999, Sect. 4, p. 14; Service 2011, p. 61831). However, since the time of Furnish and Monthey's conclusions in 1999, the number of known locations has increased from 2 to 21, 10 of which are on protected State or Federal lands (Furnish and Monthey 1999, Sect. 4, pp. 10, 11; Johannes 2012a, pp. 2-7; Johannes 2012b, p. 11; PGE 2011, pp. 26, 37; PGE 2012 p. 27). The SMP (discussed above) has also been reinstated on Federal lands subject to the NWFP. Various habitat improvement measures have been carried out in the upper Fall River drainage, where the majority of occupied sites on private land are located (FRRCD 2005, pp. 1-3). Habitat improvements include exclusion fencing to keep cattle from streambanks, bank stabilization projects, and the replacement and upgrade of a railroad crossing that had collapsed twice in the past (producing extensive siltation on those occasions) (FRRCD 2005, p. 2; Ellis and Haley 2012, p. 1). Landowners also took steps to reduce the potential for serious wildfires and to prevent erosion of sediment from a nearby meadow (FRRCD 2005, p. 3). In Hat Creek, grazing has been eliminated in the general vicinity of the PGE dams since 2001 (Stewardship Council 2007, Vol. 2, p. PM-31). Grazing has also been eliminated from lands surrounding the two privately owned sites occupied by canary duskysnails in the lower Pit River. Forestry has been eliminated in areas near those sites conducted in accordance with a conservation plan developed and implemented by a nonprofit land-management corporation (seeGrazing and Loggingunder Nugget Pebblesnail, below) (Stewardship Council, Vol. 2, pp. PM 38, 40, 41, 48, 50).

The Shasta crayfish is a federally endangered species that shares essentially the same native range and habitat requirements as the canary duskysnail (Service 2009, pp. 4-6). The two species often co-occur at the same locations (Hershleret al.2003, p. 280). When we listed the Shasta crayfish in 1988, we identified grazing, pollution, and water use for residential development as threats to the species (Service 1988, p. 38463). In our 2009 review of the species' status, however, we determined those practices no longer constitute significant impacts to the species (Service 2009, p. 9).

Summary of Factor A

In summary, no clear population trends in response to habitat modifications are evident at any of the sites occupied by canary duskysnails, including the eight sites monitored by PGE. The release of additional Pit River waters from the dams under PGE's new licensing agreements does not appear to have resulted in adverse effects on downstream canary duskysnail populations. We also know of no occupied sites that have been permanently lost due to habitat modifications, although population fluctuations at some of the monitored sites included densities of zero during some years. No cause of the fluctuations at the monitored sites was evident. We therefore conclude, based on the best available scientific and commercial data, that the present or threatened destruction, modification or curtailment of its habitat or range does not constitute a significant threat to the species now or in the future.

Factor B. Overutili