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Home , Cutthroat trout, Oncorhynchus

SPECIES: Scientific [common] clarkii lewisi [Westslope cutthroat ] Forest: -Challis National Forest Forest Reviewer: Bart L. Gamett Date of Review: March 16, 2018 Forest concurrence (or No recommendation if new) for inclusion of species on list of potential SCC: (Enter Yes or No)

FOREST REVIEW RESULTS:

1. The Forest concurs or recommends the species for inclusion on the list of potential SCC: Yes___ No_X__ Other: __ (see explanation below)

The contractor recommended that this species not be designated as a SCC. The Forest and Region concurred with this recommendation.

2. Rationale for not concurring is based on (check all that apply): Species is not native to the plan area ______Species is not known to occur in the plan area ______Species persistence in the plan area is not of substantial concern ______

FOREST REVIEW INFORMATION:

1. Is the Species Native to the Plan Area? Yes_X__ No___

If no, provide explanation and stop assessment.

2. Is the Species Known to Occur within the Planning Area? Yes_X__ No___

If no, stop assessment.

Table 1. Selected sampling events (not inclusive) where Westslope have been detected on the Salmon-Challis National Forest within the Salmon basin.

Location (4th Field HUC) Year Observed Source Information Middle Salmon-Chamberlain 1995 Liter et al. (1999) (17060207) Middle Salmon-Panther 2016 Messner et al. (in (17060203) 2009, 2010, 2011, 2012, preparation) 2013, 2015 SCNF, unpublished data1 2001, 2002 1995 Bartel et al. (2009) Liter et al. (1999) Upper Salmon 2016 Messner et al. in preparation (17060201) 2001, 2004-2015 Williams et al. (2016) 2001, 2002, 2003 Bartel et al. (2009) 2003, 2004, 2006, 2007 Gamett and Bartel (2008) 2003, 2004, 2005 Schoby and Curer (2007) Lower Middle Fork Salmon 2016 Messner et al. in preparation (17060206) 1993, 1996, 1999, 2003- Williams et al. (2016) 2005, 2007, 2009, 2010, 2012-2015 Gamett and Bartel (2011) 2002, 2004, 2005, 2006, 2007 Upper Middle Fork Salmon 2016 Messner et al. in preparation (17060205) 2009, 2010, 2012, 2014 Williams et al. (2016) 2004, 2005, 2006, 2007, 2008 Gamett and Bartel (2011) Lemhi 2009, 2010, 2012, 2013 SCNF, unpublished data1 (17060204) Pahsimeroi 2002, 2004, 2007, 2009-2015 Williams et al. (2016) (17060202) 2001, 2002, 2003 Bartel et al. (2009) 1 Unpublished electrofishing data collected by the Salmon-Challis National Forest from the Middle Salmon-Panther and Lemhi River watersheds.

References:

Bartel, J. A., B. L. Gamett, and J. C. Pyron. 2004. The Status of Fishes on the Challis Ranger District, Salmon-Challis National Forest (2001-2004). Zone Fish Program, Lost River and Challis Ranger Districts, Salmon-Challis National Forest. Pp. 235.

Gamett, B. L. and J. A. Bartel. 2008. The Status of Fishes on the Yankee Fork Ranger District, Salmon-Challis National Forest. South Zone Fish Program, Salmon-Challis National Forest. Pp. 146.

Gamett, B. L. and J. A. Bartel. 2011. The Status of Fishes on the Middle Fork Ranger District, Salmon-Challis National Forest (2002-2008). South Zone Fish Program, Salmon-Challis National Forest. Pp. 176.

Liter, M., T. Curet, and M. Larkin. 1999. Regional fisheries management investigations Salmon region (Subprojects I, II, III, IV). Department of Fish and Game. Federal Aid in Fish Restoration. Job Performance Report Program F-71-R-20.

Messner, J., J. Hansen, B. Beller, G. Schoby. In prep. Idaho Department of Fish and Game Fisheries Management General Report. Salmon Region 2016. Pp. 186.

Messner, J., G. Schoby, M. Belnap, M. Amick, and J. Loffredo. In prep. Idaho Department of Fish and Game Fisheries Management General Report. Salmon Region 2015. Pp. 186. Pp. 166.

Messner, J., J. Hansen, B. Beller, G. Schoby. In prep. Idaho Department of Fish and Game Fisheries Management General Report. Salmon Region 2014. Pp. 152.

Schoby, G. P., and T. Curet. 2007. Seasonal migrations of , Westslope Cutthroat Trout, and in the Upper Salmon River Basin, Idaho. Report 2003, 2004, 2005. Idaho Department of Fish and Game, Boise, ID.

a. Are all Species Occurrences Only Accidental or Transient?

Yes___ No_X__

If yes, document source for determination and stop assessment. b. For species with known occurrences on the Forest since 1990, based on the number of observations and/or year of last observation, can the species be presumed to be established or becoming established in the plan area?

Yes_X__ No___

If no, provide explanation and stop assessment

c. For species with known occurrences on the Forest predating 1990, does the weight of evidence suggest the species still occurs in the plan area?

Yes___ No___

Provide explanation for determination

N/A— occurrences have been documented since 1990.

If determination is no, stop assessment d. Map 1, Westslope cutthroat trout (Oncorhynchus clarkii lewisi) range in Idaho (IDFG 2017a)

IDFG (Idaho Department of Fish and Game). 2017a. Westslope cutthroat trout (Oncorhynchus clarkii lewisi). Internet website: https://idfg.idaho.gov/species/taxa/80442. Accessed on December 21, 2017.

e. Map 2, Westslope cutthroat trout (Oncorhynchus clarkii lewisi) range in (MNHP and MFWP 2017).

Note: Although the species occurs in Montana, there are no connections to the population on the Forest.

MNHP and MFWP (Montana Natural Heritage Program and Montana Fish, Wildlife, and Parks). 2017. Montana Field Guides—Westslope cutthroat trout (Oncorhynchus clarkii lewisi). Internet website: http://fieldguide.mt.gov/speciesDetail.aspx?elcode=AFCHA02088. Accessed on December 21, 2017.

f. Map 3, The distribution of native Westslope Cutthroat Trout on the Salmon-Challis National Forest. Map shows HUC4s in which native fish are present (Table 1) or absent.

3. Is There Substantial Concern for the Species’ Capability to persist Over the Long-term in the Plan Area Based on Best Available Scientific Information?

Table 2. Status summary based on existing conservation assessments

Entity Status/Rank (include definition if Other) NatureServe G4T4—Apparently Secure global population and infraspecific taxa (Uncommon but not rare; some cause for long-term concern Global Rank due to declines or other factors) NatureServe S4—Apparently Secure (Uncommon but not rare; some cause for long-term concern due to declines or other factors State Rank State List IDFG— Status No SGCN status

USDA Forest Region 4 sensitive species Service

USDI FWS No records found Other BLM sensitive species 2— Rangewide/Globally Imperiled Species (These are species that are experiencing significant declines throughout their range with a high likelihood of being listed in the foreseeable future due to their rarity and/or significant endangerment factors)

Table 3. Status summary based on best available scientific information.

Species (Scientific and Common Name): Oncorhynchus clarkii lewisi (Westslope cutthroat trout)

Criteria Rank Rationale Literature Citations 1 C2 Westslope cutthroat trout, a of cutthroat trout, are native to IDFG (Idaho Department of Fish Distribution on the Salmon River basin and occur on the Salmon–Challis National Forest and Game). 2013a. Management Salmon-Challis in many waters within this drainage (USFS 2017a). Introduced plan for the conservation of National Forest populations also occur as a result of high-density stocking to support westslope cutthroat trout. Internet recreational fisheries (IDFG 2013a; Messner et al. 2016). However, this website: assessment is focused on the native populations that occur on the http://www.fwspubs.org/doi/suppl portion of the Salmon–Challis National Forest within the Salmon River /10.3996/012015-JFWM-

Species (Scientific and Common Name): Oncorhynchus clarkii lewisi (Westslope cutthroat trout)

Criteria Rank Rationale Literature Citations Basin. 001/suppl_file/012015-jfwm- 001.s8.pdf?code=ufws-site. Westslope cutthroat trout occur on the Forest in numerous and Accessed on December 21, 2017. hundreds of miles of streams within the Salmon River Basin, and thus are widely distributed throughout this area (Rank C2). Messner et al. 2016. Idaho Department of Fish and Game fisheries management annual Confidence in Rank: High, Medium, or Low report. Salmon region 2014. IDFG # 16-103.

USFS (United States Department of Agriculture, Forest Service). 2017a. Salmon–Challis National Forest Draft Assessment Report. October 2017. 2 C Of the 14 subspecies of cutthroat trout found in Western , Behnke, R. J. 1979. Monograph of Distribution in westslope cutthroat trout is the most widely distributed (IDFG 2013a). It the native of the surrounding inhabits streams on both sides of the Continental Divide, from of western North America. geographic area northwestern Montana and central Idaho into southern USDA Forest Service, Fish and and . West of the divide, this subspecies is thought to be native to Wildlife Service, Bureau of Land several major drainages of the basin, including the upper Management. Kootenai River drainage from its headwaters in British Columbia, through northwest Montana, and into northern Idaho; the Clark Fork River IDFG (Idaho Department of Fish drainage of Montana and Idaho downstream to the falls on the Pend and Game). 2013a. Management Oreille River near the –British Columbia border; the Spokane plan for the conservation of River above Spokane Falls and into Idaho's Coeur d'Alene and St. Joe westslope cutthroat trout. Internet River drainages; and the Salmon and Clearwater River drainages of Idaho website: (Behnke 1979; NatureServe 2017). East of the divide, the native http://www.fwspubs.org/doi/suppl distribution includes the headwaters of the South Saskatchewan River /10.3996/012015-JFWM- drainage (United States and ); the entire drainage 001/suppl_file/012015-jfwm-

Species (Scientific and Common Name): Oncorhynchus clarkii lewisi (Westslope cutthroat trout)

Criteria Rank Rationale Literature Citations upstream from Fort Benton, Montana, and extending into northwest 001.s8.pdf?code=ufws-site. ; and the headwaters of the Judith, Milk, and Marias , Accessed on December 21, 2017. which join the Missouri River downstream from Fort Benton. Additionally, there are several disjunct populations in , NatureServe. 2017. NatureServe Washington, and British Columbia (Behnke 1979; NatureServe 2017). Explorer: An online encyclopedia of life [web application]. Version 7.1. Therefore, the westslope cutthroat is widely distributed outside the NatureServe, Arlington, Virginia. Salmon-Challis National Forest (Rank C). Internet website: http://explorer.natureserve.org. Confidence in Rank: High, Medium, or Low Accessed December 21, 2017. 3 C Westslope cutthroat trout have three possible life forms defined by IDFG (Idaho Department of Fish Dispersal migration patterns: lacustrine–adfluvial (migrate between lakes and and Game). 2013a. Management Capability streams); fluvial–adfluvial (move between mainstem rivers and plan for the conservation of ); and fluvial or resident (stay in small headwater streams); all westslope cutthroat trout. Internet three life history forms may occur within a single basin (IDFG 2013a). website: Resident populations generally spend their entire lives in tributaries, http://www.fwspubs.org/doi/suppl exhibit relatively small amounts of genetic diversity within a particular /10.3996/012015-JFWM- local population, and have higher levels of genetic diversity between 001/suppl_file/012015-jfwm- stream populations and tributaries. Migratory trout can travel several 001.s8.pdf?code=ufws-site. hundred kilometers between adult and spawning habitat, and Accessed on December 21, 2017. populations exhibit some degree of flow (IDFG 2013a). IDFG (Idaho Department of Fish In the Upper Salmon River basin, the average one-way migration distance and Game). 2017b. Idaho State between winter habitat and spawning habitat for radio tagged westslope Wildlife Action Plan, 2015. Boise, cutthroat trout was 84.1 km (52.3 mi). Although migrations into ID. tributaries were not documented in the majority of tagged individuals, considerable movements within the Salmon River were observed, Schoby, G. P., and T. Curet. 2007. possibly associated with the search for suitable habitat or preceding Seasonal migrations of Bull Trout, spawning migrations (Schoby and Curet 2007). Westslope Cutthroat Trout, and Rainbow Trout in the Upper Salmon

Species (Scientific and Common Name): Oncorhynchus clarkii lewisi (Westslope cutthroat trout)

Criteria Rank Rationale Literature Citations Barriers such as dams, diversions, and culverts can isolate habitats and River Basin, Idaho. Report decrease the likelihood of persistence of some fluvial trout populations. 2003, 2004, 2005. Idaho Elevated water temperatures in the Salmon River and major tributaries Department of Fish and Game, resulting from dewatering may also represent seasonal migration Boise, ID. barriers (Schoby and Curet 2007). Although habitat fragmentation is cited as a primary threat to westslope cutthroat on the Forest (USFS 2017a), USFS (United States Department of the density of diversions on the Forest is low (USFS 2017b) and many of Agriculture, Forest Service). 2017a. the Salmon River drainages provide large connected habitats for Salmon–Challis National Forest salmonids (IDFG 2017b). Therefore, the westslope cutthroat in this Draft Assessment Report. October region can readily disperse (Rank C). 2017.

Confidence in Rank: High, Medium, or Low USFS (United States Department of Agriculture, Forest Service). 2017b. Salmon–Challis National Forest Riparian Assessment (Draft a). 4 C Westslope cutthroat trout habitat and populations have declined from Bartel, J. A., B. L. Gamett, and J. C. Abundance on the historical levels (IDFG 2005). This subspecies is estimated to currently Pyron. 2004. The Status of Fishes Salmon-Challis occupy 54,075 km (33,608 mi) or 58% of nearly 93,370 km (58,030 mi) of on the Challis Ranger District, National Forest historically occupied habitat, including 27,784 km (17,268 mi) in Idaho Salmon-Challis National Forest (51% of current distribution) (Shepard et al. 2005). Stream segments that (2001-2004). Zone Fish Program, support westslope cutthroat trout “slightly below” to “near” habitat Lost River and Challis Ranger capacity represent about 50% of the historical range (IDGF 2005; Shepard Districts, Salmon-Challis National et al. 2003). Forest. Pp. 235.

A more recent assessment (IDFG 2013a) found that the subspecies IDFG (Idaho Department of Fish inhabits up to 80% of its historical range in Idaho, with the healthiest and Game). 2005. Westslope populations occurring within federally protected lands. Many wilderness cutthroat trout (Oncorhynchus streams located in the central Idaho batholith, which intersects the clarki lewisi). Internet website: Forest, have inherently low productivity, and thus the density of https://idfg.idaho.gov/ifwis/cwcs/p

Species (Scientific and Common Name): Oncorhynchus clarkii lewisi (Westslope cutthroat trout)

Criteria Rank Rationale Literature Citations westslope cutthroat is also relatively low, even though their abundance is df/Westslope%20Cutthroat%20Tro at or near capacity (Shepard et al. 2003). ut.pdf. Accessed on December 21, 2017. Surveys on the Challis, Yankee Fork, and Middle Fork Ranger Districts of the Forest indicate that cutthroat trout is the most widely distributed IDFG (Idaho Department of Fish species on all three districts, with densities as high as 51.8 fish/100 m2 in and Game). 2013a. Management Eddy Creek; however, these surveys did not distinguish subspecies and plan for the conservation of included cutthroat trout x rainbow trout hybrids (Gamett and Bartel westslope cutthroat trout. Internet 2008, 2011; Bartel et al. 2004). Ongoing surveys for westslope cutthroat website: trout in Idaho (IDFG 2013a) indicated relative low densities in most http://www.fwspubs.org/doi/suppl general management units (GMUs) that intersect the Forest [e.g., the /10.3996/012015-JFWM- mainstem Lemhi River (0.006 trout/100 m2; SE ± 0.005), Pahsimeroi River 001/suppl_file/012015-jfwm- (0.11 trout/100 m2; SE ± 0.05), Upper Salmon River (0.83 trout/100 m2; 001.s8.pdf?code=ufws-site. SE ± 0.35)], but higher densities in tributaries such as Kinnikinic Creek Accessed on December 21, 2017. (7.23 trout/100 m2; SE ± 0.51), Bayhorse Creek (6.87 trout/100 m2; SE ± 2.26), Wagonhammer Creek (18.73 trout/100 m2; SE ± 2.39), and Pattee Gamett, B. L. and J. A. Bartel. 2008. Creek (23.26 trout/100 m2; SE ± 13.38). The Status of Fishes on the Yankee Fork Ranger District, Salmon-Challis Therefore, westslope cutthroat trout occur at various densities on the National Forest. South Zone Fish Forest, but are expected to be well distributed where suitable habitat Program, Salmon-Challis National occurs (Rank C). Medium confidence was chosen in light of the spatial Forest. Pp. 146. variation in in abundance across the Forest. Gamett, B. L. and J. A. Bartel. 2011. The Status of Fishes on the Middle Confidence in Rank: High, Medium, or Low Fork Ranger District, Salmon-Challis National Forest (2002-2008). South Zone Fish Program, Salmon-Challis National Forest. Pp. 176.

Shepard, B. B., B. E. May, and W.

Species (Scientific and Common Name): Oncorhynchus clarkii lewisi (Westslope cutthroat trout)

Criteria Rank Rationale Literature Citations Urie. 2003. Status of Westslope Cutthroat Trout (Oncorhynchus clarki lewisi) in the United States: 2002. 5 B Surveys for westslope cutthroat throughout Idaho suggest that Kennedy, P. and K. A. Meyer. 2014. Population Trend populations are generally stable or increasing in abundance across much Trends in the abundance of on the Salmon- of the state (Kennedy and Meyer 2014). Populations in the mid-Salmon westslope cutthroat trout in Idaho. Challis National River showed a statistically significant population decline; those in the Wild trout symposium XI—Looking Forest South Fork Salmon River declined or were stable (90% error bounds that back and moving forward (2014). overlapped zero); populations in the Middle Fork Salmon River increased Session 7: Wild trout monitoring— or were stable; and those in the Upper Salmon River were stable 309. (Kennedy and Meyer 2014). USFS (United States Department of Therefore, populations appear stable in many areas on the Forest (Rank Agriculture, Forest Service). 2017a. B), although populations have likely declined in some areas and may have Salmon–Challis National Forest been completely eliminated in other areas (USFS 2017a). Medium Draft Assessment Report. October confidence was chosen in light of the spatial variation in in population 2017. trends across the Forest.

Confidence in Rank: High, Medium, or Low 6 B Westslope cutthroat trout inhabit streams, lakes, and reservoirs IDFG (Idaho Department of Fish Habitat Trend on throughout the Forest (USFS 2017a). They require well-oxygenated and Game). 2005. Westslope the Salmon-Challis water; clean, well-sorted gravels with minimal fine sediments for cutthroat trout (Oncorhynchus National Forest successful spawning; cool temperatures [<21°C (<70°F)]; nutrient-poor clarki lewisi). Internet website: water; water velocities ranging from 0.1 to 0.3 m/s; and complex https://idfg.idaho.gov/ifwis/cwcs/p instream habitat structure with numerous pools and some form of cover df/Westslope%20Cutthroat%20Tro (IDFG 2005, 2013a). Adfluvial cutthroat spend 1–4 years as juveniles in ut.pdf. Accessed on December 21, streams before moving into lakes. If other species are present in the 2017. lakes, westslope cutthroat will use nearshore, littoral areas or disperse throughout the . Adult fluvial fish overwinter in deeper pools (IDFG IDFG (Idaho Department of Fish

Species (Scientific and Common Name): Oncorhynchus clarkii lewisi (Westslope cutthroat trout)

Criteria Rank Rationale Literature Citations 2005). and Game). 2013. Management plan for the conservation of Riverine–riparian systems of the Salmon River basin provide key habitat westslope cutthroat trout. Internet for native westslope cutthroat trout. The continued connectivity and website: reconnection of these riverine systems is vital to achieving sustainable http://www.fwspubs.org/doi/suppl fisheries in this region (IDFG 2017b). Many of the Salmon River drainages /10.3996/012015-JFWM- have good to excellent viability due to the free-flowing status of the 001/suppl_file/012015-jfwm- Salmon River and its primary tributaries (e.g., no synthetic barriers), large 001.s8.pdf?code=ufws-site. connected habitats for listed salmonids, and an abundance of roadless Accessed on December 21, 2017. and little-roaded federal lands with high ecological integrity. These areas may serve as habitat strongholds for cutthroat. However, areas of poor IDFG (Idaho Department of Fish to fair riparian viability attributed to irrigated agriculture, livestock and Game). 2017b. Idaho State grazing, road construction, logging, and mining also occur, and have led Wildlife Action Plan, 2015. Boise, to alteration of stream hydrographs and lowered water quality due to ID. loss of thermal cover along streams, loss of filtering functions, and decreased bank stability in some areas (IDFG 2017b). USFS (United States Department of Agriculture, Forest Service). 2017a. Because westslope cutthroat require cool, oligotrophic water with low Salmon–Challis National Forest levels of fine sediment, water quality and temperature are important Draft Assessment Report. October habitat characteristics. Based on indicators for water quality in surface 2017. water systems, 41% of the Forest is within the natural range of variation (NRV), 34% is trending toward the NRV, and 1% is outside the NRV, in USFS (United States Department of land type associations (LTAs) with sufficient information. However, for Agriculture, Forest Service). 2017b. LTAs on the Forest with sufficient data, water temperature was Salmon Challis National Forest Data significantly altered in more than 15% of watersheds (USFS 2017b). Assessment, Riparian Section (Draft a). Herbaceous and woody riparian plants enhance salmonid habitat by stabilizing soil, creating overhanging banks, and shading streams. Based on LTAs with sufficient information, the condition and composition of riparian ecosystems on the Forest are within or trending towards the

Species (Scientific and Common Name): Oncorhynchus clarkii lewisi (Westslope cutthroat trout)

Criteria Rank Rationale Literature Citations NRV at the majority of land type associations (USFS 2017).

The fluctuation in surface and groundwater levels is a key ecosystem characteristic that influences the structure and function of all riparian and aquatic systems. Of the area assessed on the Forest for assessed for changes in ground and surface water fluctuations, 11% is outside the NRV and 79% is trending towards the NRV (USFS 2017b).

Channel and floodplain dynamics, including flooding, channel avulsion, cut and fill alluviation, recruitment of large woody debris, and regeneration of vegetation, is also an important characteristic of riparian ecosystems. Of the Forest area that has been assessed for changes in channel and floodplain dynamics, 17% is outside the NRV and 49% is trending towards the NRV (USFS 2017b).

Overall, suitable habitat for westslope cutthroat trout on the Forest has declined relative to historic conditions (Rank A). However, several indicators suggest that suitable habitat is currently improving. Confidence is medium because indicators have not been assessed across the entire Forest.

Confidence in Rank: High, Medium, or Low 7 A Reduced habitat is a primary threat to westslope cutthroat trout on the IAP (Intermountain Adaption Vulnerability of Forest and can occur from a variety of factors (USFS 2017a). A legacy of Partnership). 2016. Intermountain Habitats on the fire suppression on the Forest has increased the frequency and intensity Adaption Partnership: Climate Salmon-Challis of major wildfires in recent decades (USFS 2017c); these large, non- Vulnerability Assessment National Forest typical wildfires lead to very unstable soil and slope conditions that may Summaries (Draft). cause chronic sediment release (USFS 2017b), which reduces emergence success, embryo survival, and food and space for rearing juveniles (IDFG IDFG (Idaho Department of Fish 2013a). Roads and recreation can also increase sedimentation and and Game). 2013a. Management

Species (Scientific and Common Name): Oncorhynchus clarkii lewisi (Westslope cutthroat trout)

Criteria Rank Rationale Literature Citations degradation of streambank integrity. Of the roughly 4200 miles of roads plan for the conservation of on the Forest, about 66% are classified as unimproved (USFS 2017b). westslope cutthroat trout. Internet Livestock grazing, which can also decrease water quality and streambank website: stability, occurs throughout much of the Forest, including the parts of http://www.fwspubs.org/doi/suppl Lower Middle Fork Salmon, Upper Salmon, Pahsimeroi, Lemhi, and /10.3996/012015-JFWM- Middle Salmon–Panther sub-basins. No active grazing allotments occur 001/suppl_file/012015-jfwm- on the Middle Salmon–Chamberlin, and only a small area (15,281 acres) 001.s8.pdf?code=ufws-site. of active grazing occurs on the Upper Middle Fork Salmon, as much of Accessed on December 21, 2017. these basins occur on wilderness areas (USFS 2016a; USFS 2017a). Although impacts have been substantial in some areas, grazing levels are IDFG (Idaho Department of Fish believed to be much lower than historic levels and 78% of 107 monitored and Game). 2013b. Fisheries pastures in riparian areas met percent forage utilization standards in Management Plan 2013–2018; A 2012, indicating that grazing practices are improving (Google Earth 2017; Comprehensive Guide to Managing USFS 2016b). Unrestricted timber harvest is another action that can also Idaho’s Fisheries Resources. impact westslope cutthroat trout habitat. Internet website: https://idfg.idaho.gov/old- Construction of dams, irrigation diversions, or other migration barriers web/docs/fish/planFisheries.pdf. such as culverts have isolated or eliminated areas of westslope cutthroat Accessed on January 4, 2018. habitat (McIntyre and Rieman 1995). Decreased habitat connectivity may seriously compromise the potential for long-term persistence by Google Earth. 2017. Salmon–Challis hindering potentially important metapopulation dynamics (McIntyre and National Forest, Idaho. Internet Rieman 1995). There are 205 diversions scattered across the Forest, and website: most land type associations have relatively low diversion density (USFS https://www.google.com/earth/. 2017b). Accessed on January 4, 2018. Loxterman, J. L., E. R. Keeley, and Z. Introductions of non-native trout have led to hybridization and M. Njoroge. 2014. Evaluating the introgression, which pose a significant threat to the westslope cutthroat influence of stocking history and throughout its range (Weigel et al. 2002), including in Idaho (Rieman and barriers to movement on the Apperson 1989). Past stocking of rainbow trout and non-native cutthroat spatial extent of hybridization trout throughout the westslope cutthroat’s range on the Forest may have between westslope cutthroat trout

Species (Scientific and Common Name): Oncorhynchus clarkii lewisi (Westslope cutthroat trout)

Criteria Rank Rationale Literature Citations led to limited hybridization with cutthroat trout in this area, as evidenced and rainbow trout. Can. J. Fish. by the existence of cutthroat x rainbow trout hybrids in at least three Aquat. Sci. 71: 1050–1058. ranger districts (Gamett and Bartel 2008, 2011; Bartel et al. 2004). Since 2000, IDFG began stocking only sterile rainbow trout within the GMU McIntyre, J.D., and B.E. Rieman. and, in recent decades, the IDFG began stocking only the westslope 1995. Westslope cutthroat trout. cutthroat trout subspecies into mountain lakes (IDFG 2013a), to reduce In: conservation and assessment hybridization and introgression. A recent study showed that the majority for inland cutthroat trout. General of individuals genotyped in the Salmon River Basin were classified as pure Technical Report RM-GTR-256. westslope cutthroat trout (Loxterman et al. 2014). Michael K. Young (technical editor). USDA-Forest Service. Rocky Because westslope cutthroat prefer cold water, changes in climate may Mountain Forest and Range play an important role in restricting the distribution of populations in the Experiment Station, Fort Collins, future. The maximum and minimum temperatures in the Middle Rocky . Mountain Region are projected to rise about 4° C by the mid-21st century (IAP 2016), and warming temperatures may geographically isolate USFS. 2016a. GIS Database populations in increasingly confined headwater reaches. Furthermore, Information. Last updated March increasing temperatures and a decrease in the snow to rain ratio are 30, 2016. expected to result in a smaller snowpack and earlier streamflow center timing and lower summer low flows (IAP 2016). These predicted climatic USFS (United States Forest Service) changes may limit decrease availability and connectivity for westslope Salmon-Challis National Forest. cutthroat (IDFG 2013a). 2016b. Forest plan monitoring and evaluation report: Salmon-Challis Although can be a threat to this subspecies, cutthroat National Forest: Salmon and Challis trout harvest has been prohibited within GMUs in the mainstem Salmon Forest plans FY 2012, 2013, 2014, River, mainstem Yankee Fork, and mainstem East Fork Salmon River since and 2015. 1996. In tributaries of the main Salmon River, fishing pressure is generally very light and managed with general fishing rules. In addition, pressure USFS (United States Department of from trout fishing is relieved by stocking of sterile rainbow trout (IDFG Agriculture, Forest Service). 2017a. 2013a; IDFG 2013b) and a catch-and-release program was implemented Salmon–Challis National Forest in areas of the Middle Fork Salmon River where cutthroat trout occur Draft Assessment Report. October

Species (Scientific and Common Name): Oncorhynchus clarkii lewisi (Westslope cutthroat trout)

Criteria Rank Rationale Literature Citations (i.e., from the mouth to headwaters including tributaries and alpine 2017. lakes; IDFG 2013b). USFS (United States Department of In summary, pressure from many factors that threaten this subspecies Agriculture, Forest Service). 2017b. across its range is relatively light on the Forest (e.g., diversions, Salmon–Challis National Forest introgression and hybridization, and ). Threats that are a greater Data Assessment, Riparian concern to habitat and populations on the Forest include changes in Ecosystems Section (Draft a). climate, unrestricted livestock grazing, unrestricted timber harvest, fire suppression, and roads. These factors could cause effects outside the USFS (United States Department of NRV (Rank A). Agriculture, Forest Service). 2017c. Salmon–Challis National Forest Confidence in Rank: High, Medium, or Low Terrestrial Ecosystem Assessment. Draft.

Weigel, D.E., J.T. Peterson, and P. Spruell. 2003. Introgressive hybridization between native cutthroat trout and introduced rainbow trout. Ecological Applications 13:38-50. 8 C As described under Criterion 3, there are three life history forms of IDFG (Idaho Department of Fish Life History and westslope cutthroat trout. Both lacustrine–adfluvial and fluvial–adfluvial and Game). 2013. Management Demographics fish typically live 2–3 years in tributary streams and may spend anywhere plan for the conservation of from 1 to 4 years in natal streams prior to migration. The fish begin to westslope cutthroat trout. Internet mature at age 3 and generally at age 4 or 5 (McIntyre and Rieman website: 1995). Sexually maturing adfluvial fish move into the vicinity of http://www.fwspubs.org/doi/suppl tributaries in fall and winter where they remain until they begin to /10.3996/012015-JFWM- migrate upstream in the spring. They spawn from March to July at water 001/suppl_file/012015-jfwm- temperatures near 10° C, predominantly in small tributaries with gravel 001.s8.pdf?code=ufws-site. substrate. A single spawning event produces 1000-2000 eggs; fertilized Accessed on December 21, 2017.

Species (Scientific and Common Name): Oncorhynchus clarkii lewisi (Westslope cutthroat trout)

Criteria Rank Rationale Literature Citations eggs hatch after 2 months of incubation (Spaete 2006). Fry emerge from gravel after yolk sac absorption, and many disperse downstream Loxterman, J. L., E. R. Keeley, and Z. (McIntyre and Rieman 1995). M. Njoroge. 2014. Evaluating the influence of stocking history and Cutthroat trout are not exceptionally long-lived fish, and may live barriers to movement on the anywhere from 6-8 years (Spaete 2006). Substrate composition is spatial extent of hybridization believed to strongly influence survival. Substrate composition, between westslope cutthroat trout particularly the percentage of fine sediment, strongly influences survival and rainbow trout. Can. J. Fish. of early life history phases. Elevated levels of fine sediment reduce Aquat. Sci. 71: 1050–1058. emergence success, embryo survival, and food and space for rearing juveniles. In addition, highly embedded substrates may be harmful for McIntyre, J.D., and B.E. Rieman. juveniles that typically enter substrate for cover in winter (McIntyre and 1995. Westslope cutthroat trout. Rieman 1995). In: conservation and assessment for inland cutthroat trout. General In Columbia River tributaries, the westslope cutthroat is commonly Technical Report RM-GTR-256. associated with bull trout, resident and anadromous rainbow trout or Michael K. Young (technical editor). steelhead, and , and competition and have USDA-Forest Service. Rocky been linked to declines of westslope cutthroat in lakes and streams Mountain Forest and Range (McIntyre and Rieman 1995). Non-native rainbow trout occupy Experiment Station, Fort Collins, approximately 36% of currently occupied stream within the westslope Colorado. cutthroat range in Idaho, whereas Yellowstone cutthroat have been documented in less than 1% of habitat (IDFG 2013a). , which NatureServe. 2017. NatureServe overlaps over half of the westslope cutthroat’s occupied range in Idaho, Explorer: An online encyclopedia of are thought to have replaced cutthroat trout in many streams across life [web application]. Version 7.1. their historical range in Idaho (Rieman and Apperson 1989; IDFG 2013a). NatureServe, Arlington, Virginia. The westslope cutthrout’s distribution overlaps with that of brook trout, Internet website: rainbow trout, and chinook salmon in at least three ranger districts on http://explorer.natureserve.org. the Forest (Gamett and Bartel 2008, 2011; Bartel et al. 2004), and Accessed December 21, 2017. therefore, competition between these species likely exists. The westslope cutthroat’s diet, which mainly consists of terrestrial and Rieman, B.E., and K.A. Apperson.

Species (Scientific and Common Name): Oncorhynchus clarkii lewisi (Westslope cutthroat trout)

Criteria Rank Rationale Literature Citations aquatic insects and with relatively few fish, may be an 1989. Status and analysis of evolutionary adaptation to alleviate competition with highly piscivorous salmonid fisheries: westslope fish (McIntyre and Rieman 1995). cutthroat trout synopsis and analysis of fishery information. As described in Criterion 7, hybridization and introgression with non- Project F-73-R-11. Federal Aid in native trout are a significant threat to westslope cutthroat in Idaho Fish Restoration. Idaho Department (Rieman and Apperson 1989). There are two schools of thought regarding of Fish and Game. Boise. conservation strategies for this subspecies—isolation of genetically pure populations and maintenance of habitat connectivity (Shepard et al. Shepard, B. B., B. E. May, and W. 2005). While isolation can prevent upstream invasions by non-native Urie. 2003. Status of Westslope salmonids and reduce risks from genetic introgression, competition, and Cutthroat Trout (Oncorhynchus disease, the lack gene flow between metapopulations may compromise clarki lewisi) in the United States: the potential for long-term persistence (Loxterman et al. 2014; Shepard 2002. et al. 2005). Because the majority of individuals in the Salmon River Basin were classified as pure westslope cutthroat trout (Loxterman et al. 2014), Spaete, L. 2006. Oncorhynchus these issues are probably not a major concern on the Forest. clarkii. Diversity Web. Internet website: Given their high reproductive rates but several factors that threaten http://animaldiversity.org/account survival (competition, predation, water quality), westslope cutthroat s/Oncorhynchus_clarkii/. Accessed trout have a moderate ability to recover from disturbance (Rank B). December 28, 2017.

Confidence in Rank: High, Medium, or Low Summary and recommendations: Current conservation assessments indicate moderate rangewide concern for the Date: 12/22/2017 westslope cutthroat trout—this subspecies is considered a sensitive species in Forest Service Region 4 and a BLM Type 2 sensitive species (Rangewide/Globally Imperiled Species), but not a Species of Greatest Conservation Need. The westslope cutthroat is the most widely distributed of the 14 subspecies of cutthroat trout that occur in western North America. However, habitat and populations have declined from historical levels, and only about 58% of the historic range is currently occupied. This subspecies naturally occurs at low densities, and surveys on the Forest indicate that populations are probably stable. Riparian assessment indicators including water quality, riparian conditions, channel and floodplain dynamics, and surface and groundwater levels indicate that suitable habitat on

Species (Scientific and Common Name): Oncorhynchus clarkii lewisi (Westslope cutthroat trout)

Criteria Rank Rationale Literature Citations the Forest has deteriorated from historic conditions, but is largely improving.

Significant threats on the Forest include climate change, unrestricted livestock grazing, unrestricted timber harvest, fire suppression, and roads, but pressure from several main threats across its range (diversions, introgression and hybridization, and angling) is relatively light on the Forest. For example, although rainbow trout overlap a large portion of the westslope cutthroat’s range in Idaho, the majority of individuals genotyped in the Salmon River Basin were classified as pure westslope cutthroat trout and stocked fish are now sterilized. In addition, the density of diversions on the Forest is low.

Considering their wide range, common abundance, stable population trends, and absence of several major threats on the Forest, the westslope cutthroat is not recommended as a SCC.

Evaluator(s): Lindsay Chipman and Bart Gamett

Forest Recommendation: This analysis indicates there is not substantial concern for the capability of Oncorhynchus clarkii lewisi to persist over the long-term on the Salmon-Challis National Forest. Therefore, it is recommended that Oncorhynchus clarkii lewisi not be designated as a Species of Conservation Concern.