Salvelinus confluentus - (Suckley, 1859)
Bull Trout
Taxonomic Status: Accepted
Related ITIS Name(s): Salvelinus confluentus (Suckley, 1859) (TSN 162004)
French Common Names: omble à tête plate
Unique Identifier: ELEMENT_GLOBAL.2.106067
Element Code: AFCHA05020
Informal Taxonomy: Animals, Vertebrates - Fishes - Bony Fishes - Salmon and Trouts
 
Kingdom Phylum Class Order Family Genus
Animalia Craniata Actinopterygii Salmoniformes Salmonidae Salvelinus
Genus Size: C - Small genus (6-20 species)
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Concept Reference
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Concept Reference: Robins, C.R., R.M. Bailey, C.E. Bond, J.R. Brooker, E.A. Lachner, R.N. Lea, and W.B. Scott. 1991. Common and scientific names of fishes from the United States and Canada. American Fisheries Society, Special Publication 20. 183 pp.
Concept Reference Code: B91ROB01NAUS
Name Used in Concept Reference: Salvelinus confluentus
Taxonomic Comments: The bull trout is a member of the S. alpinus complex. It was long confused with look-alike S. malma (Dolly Varden), especially where the ranges overlap on the Pacific slope (Lee et al. 1980). McPhail (1961) regarded S. confluentus as conspecific with S. malma. Cavender (1978) demonstrated the specific distinctiveness of S. confluentus, but hybridization and some introgression occur across a broad area of contact. Additionally, molecular data indicate that historical introgression of bull trout mtDNA into Dolly Varden occurred sometime prior to the most recent glaciation (Redenbach and Taylor 2002).

Genetic studies by Allendorf at the Univeristy of Montana suggest that Klamath River basin populations may be distinctive; further study of variation is needed (Starnes 1995).

Genetic studies suggest that the bull trout comprises two or more clades that originated from distinct glacial refugia on either side of the Cascade/Coast Mountains (see review in Costello et al. 2003). Genetic data indicate that bull trout tend to show high levels of population subdivision in localized areas; hence local populations likely have high levels of demographic independence (Costello et al. 2003). Bull trout exhibit apparently low levels of intrapopulation molecular variation (Costello et al. 2003).

Sterile hybrids arise from cross with S. fontinalis.
Conservation Status
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NatureServe Status

Global Status: G4
Global Status Last Reviewed: 04Nov2011
Global Status Last Changed: 04Nov2011
Ranking Methodology Used: Ranked by inspection
Rounded Global Status: G4 - Apparently Secure
Reasons: Ranges from extreme southern Yukon to northern California and northern Nevada; greatly reduced in range and numbers south of Canada, but many occurrences remain in the core of the range; many streams contain exotic congeners that compete for spawning females; trend over the past 10 years or three generations is relatively stable in the major portion of the range in British Columbia.
Nation: United States
National Status: N4 (04Nov2011)
Nation: Canada
National Status: N3N4 (08Mar2013)

U.S. & Canada State/Province Status
United States Alaska (SNR), California (SX), Idaho (S3), Montana (S2), Nevada (S1), Oregon (S3), Washington (S3)
Canada Alberta (S3), British Columbia (S3S4), Northwest Territories (S2), Yukon Territory (S3)

Other Statuses

Implied Status under the U.S. Endangered Species Act (USESA): PS:LT,XN
Comments on USESA: USFWS (Federal Register, 10 June 1994, 12 June 1995) found that listing bull trout throughout its range was not warranted due to unavailable or insufficient data regarding threats to and status and population trends of the species in Alaska and Canada; however, USFWS found that listing the species within the coterminous U.S. was warranted but precluded by other higher priority listing actions.

USFWS (1998) listed the Klamath River population segment (south-central Oregon) and the Columbia River population segment (Idaho, Montana, Washington, Oregon, British Columbia) as Threatened, and the coastal-Puget Sound (Washington) and St. Mary-Belly River (northwestern Montana) population segments were proposed as Threatened. USFWS (1999) listed the Jarbridge River population segment as Threatened. USFWS (1999) listed the coastal-Puget Sound and St. Mary-Belly River segments as threatened, thus making the bull trout threatened throughout its entire range in the coterminous United States.

USFWS (2011) established a nonessential experimental population (NEP) in the Clackamas River and its tributaries in Clackamas County, Oregon.

U.S. Fish & Wildlife Service Lead Region: R1 - Pacific
Implied Status under the Committee on the Status of Endangered Wildlife in Canada (COSEWIC):PS: T,SC,SC,NAR,DD
Comments on COSEWIC: This fish was subdivided into 5 populations and designated by COSEWIC in November 2012.
IUCN Red List Category: VU - Vulnerable

NatureServe Global Conservation Status Factors

Range Extent: 200,000-2,500,000 square km (about 80,000-1,000,000 square miles)
Range Extent Comments: North-south distribution in coastal and montane areas of Pacific Northwest between about 48 and 61 degrees N latitude, north to the Yukon and Liard river drainages in northern British Columbia and adjacent Yukon Territory (Haas and McPhail 1991); occurs in most drainages on both sides of Continental Divide (Lee et al. 1980). Coastal and mountain streams of Arctic, Pacific, and Missouri River drainages from extreme southern Yukon through western Canada Washington, Idaho, Montana, and Oregon to the headwaters of Columbia River drainage in northern Nevada (Jarbridge River distinct population segment) and (formerly) the McCloud River drainage below Lower Falls in California (extirpated in California); locally common, rare in southern part of range; in the United States, extirpated from most of the large rivers that historically were occupied (California DF&G 1990, Page and Burr 1991).

Klamath River population segment occurs in south-central Oregon (USFWS 1997). Columbia River population segment occurs in Idaho, Montana, Oregon, Washington, and British Columbia (USFWS 1997).

Number of Occurrences: 81 - 300
Number of Occurrences Comments: This species is represented by a large number of occurrences (subpopulations).

Klamath River population segment comprises seven disconnected populations (USFWS 1997). Columbia River population segment comprises 386 populations (USFWS 1997).

Population Size: 100,000 to >1,000,000 individuals
Population Size Comments: Total adult population size is unknown but presumably exceeds 100,000.

Overall Threat Impact Comments: Hybridization appears to be a common problem where isolated or remnant resident populations overlap with introduced brook trout (spawning times and conditions are similar). Brook trout have been widely introduced and now occupy most basins inhabited by bull trout, though they often occupy different streams or stream reaches. Hybrids are likely to be sterile and experience developmental problems, and sometimes sharp declines in bull trout populations have occurred (Leary et al. 1993). In Montana, introduced brook trout progressively depressed a bull trout population. See Rieman and McIntyre (1993). In western Montana, Kanda et al. (2002) found that F1 hybrids can reproduce but they found no evidence of hybrid swarms in which all individuals are of hybrid origin. Because hybridization generally involved female bull trout and male brook trout, they concluded that hybridization represents greater wasted reproductive effort for bull trout than for brook trout.

Introduced brown trout and rainbow trout have been associated with bull trout declines, apparently due to competitive interactions; lake trout may have a negative impact on bull trout, due to predation by lake trout on juvenile bull trout, probable competitive interactions, and increased harvest associated with increased fishing pressure for lake trout (see Rieman and McIntyre 1993). Lake trout can displace bull trout and may prevent bull trout from becoming established in certain low elevation lakes (Donald and Alger 1993).

Stocked, hatchery-reared steelhead that do not migrate to the ocean (residual steelhead) sometimes migrate over 12 km upstream from their release point and may move into areas occupied by threatened stocks of bull trout (McMichael and Pearsons 2001). Residual steelhead could pose a threat through ecological interactions.

Bull trout are threatened by activities that damage riparian areas and cause stream siltation; logging, road construction, mining, and overgrazing may be harmful to spawning habitat. This species is very sensitive and severely impacted by siltation of spawning streams. Timber harvest and associated activities may have negative impacts on stream channels through sedimentation and/or increasing flooding or scour events (Rieman and McIntyre 1993).

Habitat fragmentation may be a problem, but it is unclear whether the fragmented distribution is natural due to specific habitat requirements or caused by human impacts (Rieman and McIntyre 1993). Some migratory populations have been virtually eliminated by water diversions or habitat disruption (e.g., in the Bitterroot basin) (Rieman and McIntyre 1993).

Passage through screens of water diversion structures has been a problem in some areas, but currently specified screen regulations for Pacific Northwest salmonid fry apparently do not need to be modified for bull trout fry (Zydlewski and Johnson 2002).

Climate change (warming) is a potential threat because it would decrease the amount of suitable habitat (see Rieman and McIntyre 1993).

Extirpation in California probably resulted from two factors: 1) interaction with the introduced brown trout, and 2) indirect effects resulting from the loss of the McCloud River spawning population of chinook salmon; loss of the massive influx of nutrients provided by dying salmon altered the character of the stream (Minckley and Deacon 1991).

Overharvest and illegal harvest are past and present threats, contributing to population reductions and threatening existing small populations. In response, Idaho, Montana, Oregon, and Washington have instituted strict harvest guidelines.

Electrofishing can be harmful to individual survival and reproduction (see management section).
In the Klamath River basin, bull trout are threatened by habitat degradation caused by livestock grazing, timber harvest, and water withdrawals; drought has aggravated the situation and existing land and water management and regulatory mechanisms have failed to protect populations and habitat; non-native brook trout also are a serious threat because of possible hybridization and competition; probably fewer than 5000 individuals remain in 7 fragmented populations (Fisheries Action News, Winter 1994). Each of the seven populations is at a moderate to high risk of extirpation (USFWS 1997).

Columbia River population segment is threatened by habitat degradation, passage restrictions at dams, and competition from non-native lake and brook trout.

For further information, see the threats section for individual population segments of bull trout.

Short-term Trend: Relatively Stable (<=10% change)
Short-term Trend Comments: Trend over the past 10 years or three generations is relatively stable in the major portion of the range in British Columbia.

Long-term Trend:  
Long-term Trend Comments: Has declined greatly in the contiguous 48 states, with remaining populations primarily small and/or fragmented and isolated. Range in Klamath River basin has declined drastically over the past few decades (Fisheries Action News, Winter 1994). Columbia River population segment: 33% of populations are declining, 15% are stable, 3% are secure, and 47% have unknown status (USFWS 1997). Of 65 populations surveyed in Oregon, 12 were categorized as probably extirpated and 31 had a moderate to high risk of extirpation; in Washington, 15 of 35 surveyed populations were categorized as having a moderate to high risk of extirpation (1992 publications cited by Thurow and Schill 1996). In the Flathead and Pend Oreille basins in Idaho and Montana, population trends were predominantly negative (Rieman and Myers 1997).

Other NatureServe Conservation Status Information

Inventory Needs: Better information on the current rangewide distribution and abundance is needed; inventory should include potential suitable habitat where bull trout have not yet been found (Rieman and McIntyre 1993).

Protection Needs: "Conservation of bull trout will require maintenance or restoration of multiple, high-quality, connected habitats distributed throughout conservation areas, which in turn should be distributed throughout the species' range" (Rieman and McIntyre 1993). Effective conservation of the species and its inherent diversity requires an interregional appoach (Rieman and McIntyre 1993).

Distribution
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Global Range: (200,000-2,500,000 square km (about 80,000-1,000,000 square miles)) North-south distribution in coastal and montane areas of Pacific Northwest between about 48 and 61 degrees N latitude, north to the Yukon and Liard river drainages in northern British Columbia and adjacent Yukon Territory (Haas and McPhail 1991); occurs in most drainages on both sides of Continental Divide (Lee et al. 1980). Coastal and mountain streams of Arctic, Pacific, and Missouri River drainages from extreme southern Yukon through western Canada Washington, Idaho, Montana, and Oregon to the headwaters of Columbia River drainage in northern Nevada (Jarbridge River distinct population segment) and (formerly) the McCloud River drainage below Lower Falls in California (extirpated in California); locally common, rare in southern part of range; in the United States, extirpated from most of the large rivers that historically were occupied (California DF&G 1990, Page and Burr 1991).

Klamath River population segment occurs in south-central Oregon (USFWS 1997). Columbia River population segment occurs in Idaho, Montana, Oregon, Washington, and British Columbia (USFWS 1997).

U.S. States and Canadian Provinces
Color legend for Distribution Map
Endemism: occurs (regularly, as a native taxon) in multiple nations

U.S. & Canada State/Province Distribution
United States AK, CAextirpated, ID, MT, NV, OR, WA
Canada AB, BC, NT, YT

Range Map
No map available.


U.S. Distribution by County Help
State County Name (FIPS Code)
CA Shasta (06089)*, Siskiyou (06093)*
MT Deer Lodge (30023), Flathead (30029), Glacier (30035), Granite (30039), Lake (30047), Lewis and Clark (30049), Lincoln (30053), Mineral (30061), Missoula (30063), Phillips (30071), Powell (30077), Ravalli (30081), Sanders (30089)
NV Elko (32007)
OR Baker (41001), Clackamas (41005)*, Crook (41013)*, Deschutes (41017), Douglas (41019)*, Grant (41023), Harney (41025), Hood River (41027), Jefferson (41031), Klamath (41035), Lake (41037), Lane (41039), Linn (41043), Malheur (41045), Marion (41047)*, Sherman (41055)*, Umatilla (41059), Union (41061), Wallowa (41063), Wasco (41065), Wheeler (41069)
WA Asotin (53003)+, Chelan (53007)+, Clallam (53009)+, Clark (53011)+, Columbia (53013)+, Cowlitz (53015)+, Garfield (53023)+, Grays Harbor (53027)+, Jefferson (53031)+, King (53033)+, Kittitas (53037)+, Klickitat (53039)+, Lincoln (53043)+, Mason (53045)+, Okanogan (53047)+, Pierce (53053)+, Skagit (53057)+, Skamania (53059)+, Snohomish (53061)+, Walla Walla (53071)+, Whatcom (53073)+, Yakima (53077)+
* Extirpated/possibly extirpated
U.S. Distribution by Watershed Help
Watershed Region Help Watershed Name (Watershed Code)
09 St. Marys (09040001)+, Belly (09040002)+
10 Belly (10010001), St. Mary (10010002), Beaver (10050014)+
17 Upper Kootenai (17010101)+, Fisher (17010102)+, Yaak (17010103)+, Lower Kootenai (17010104)+, Moyie (17010105), Elk (17010106)+, Upper Clark Fork (17010201)+, Flint-Rock (17010202)+, Blackfoot (17010203)+, Middle Clark Fork (17010204)+, Bitterroot (17010205)+, North Fork Flathead (17010206)+, Middle Fork Flathead (17010207)+, Flathead Lake (17010208)+, South Fork Flathead (17010209)+, Stillwater (17010210)+, Swan (17010211)+, Lower Flathead (17010212)+, Lower Clark Fork (17010213)+, Pend Oreille Lake (17010214), Priest (17010215), Pend Oreille (17010216), Upper Coeur D'alene (17010301), South Fork Coeur D'alene (17010302)*, Coeur D'alene Lake (17010303), St. Joe (17010304), Upper Spokane (17010305)*, Hangman (17010306)*, Lower Spokane (17010307), Little Spokane (17010308)*, Franklin D. Roosevelt Lake (17020001), Kettle (17020002), Sanpoil (17020004), Chief Joseph (17020005), Okanogan (17020006)*, Similkameen (17020007), Methow (17020008), Lake Chelan (17020009), Upper Columbia-Entiat (17020010), Wenatchee (17020011), Upper Yakima (17030001), Naches (17030002), Lower Yakima, Washington (17030003), Upper Snake-Rock (17040212)*, Salmon Falls (17040213)*, Little Lost (17040217), Big Wood (17040219)*, C. J. Idaho (17050101)*, Bruneau (17050102)+, Middle Snake-Succor (17050103)*, Upper Owyhee (17050104)*, South Fork Owyhee (17050105)*, East Little Owyhee. Nevada, (17050106)*, Middle Owyhee (17050107)*, Jordan (17050108)*, North and Middle Forks Boise (17050111), Boise-Mores (17050112), South Fork Boise (17050113), Lower Boise (17050114)*, Middle Snake-Payette (17050115), Upper Malheur (17050116)+, Lower Malheur (17050117)*, Bully (17050118)*, Willow (17050119)*, South Fork Payette (17050120), Middle Fork Payette (17050121), Payette (17050122), North Fork Payette (17050123), Weiser (17050124), Brownlee Reservoir (17050201)+, Burnt (17050202), Powder (17050203)+, Hells Canyon (17060101)+, Imnaha (17060102)+, Lower Snake-Asotin (17060103)+, Upper Grande Ronde (17060104)+, Wallowa (17060105)+, Lower Grande Ronde (17060106)+, Lower Snake-Tucannon (17060107), Palouse (17060108)*, Lower Snake (17060110), Upper Salmon (17060201), Pahsimeroi (17060202), Middle Salmon-Panther (17060203), Lemhi (17060204), Upper Middle Fork Salmon (17060205), Lower Middle Fork Salmon (17060206), Middle Salmon-Chamberlain (17060207), South Fork Salmon (17060208), Lower Salmon (17060209), Little Salmon (17060210), Upper Selway (17060301), Lower Selway (17060302), Lochsa (17060303), Middle Fork Clearwater (17060304), South Fork Clearwater (17060305), Clearwater (17060306), Upper North Fork Clearwater (17060307), Lower North Fork Clearwater (17060308), Walla Walla (17070102)+, Umatilla (17070103)+, Middle Columbia-Hood (17070105)+, Klickitat (17070106), Upper John Day (17070201)+, North Fork John Day (17070202)+, Middle Fork John Day (17070203)+, Lower John Day (17070204)+, Upper Deschutes (17070301)+, Little Deschutes (17070302)+*, Lower Crooked (17070305)+, Lower Deschutes (17070306)+, Trout (17070307)+*, Lower Columbia-Sandy (17080001), Lewis (17080002), Middle Fork Willamette (17090001)+, Upper Willamette (17090003)+, Mckenzie (17090004)+, North Santiam (17090005)+*, South Santiam (17090006)+*, Clackamas (17090011)+*, Lower Willamette (17090012), Hoh-Quillayute (17100101), Queets-Quinault (17100102), Upper Chehalis (17100103), Lower Chehalis (17100104), Grays Harbor (17100105), North Umpqua (17100301)*, Fraser (17110001), Strait of Georgia (17110002), Nooksack (17110004), Upper Skagit (17110005), Sauk (17110006), Lower Skagit (17110007), Stillaguamish (17110008), Skykomish (17110009), Snoqualmie (17110010), Snohomish (17110011), Lake Washington (17110012), Duwamish (17110013), Puyallup (17110014), Nisqually (17110015), Deschutes (17110016), Skokomish (17110017), Hood Canal (17110018), Puget Sound (17110019), Dungeness-Elwha (17110020), Harney-Malheur Lakes (17120001)*, Silvies (17120002)*, Summer Lake (17120005)
18 Williamson (18010201), Sprague (18010202)+, Upper Klamath Lake (18010203)+, Mccloud (18020004)+*
+ Natural heritage record(s) exist for this watershed
* Extirpated/possibly extirpated
U.S. Distribution by Watershed (based on multiple information sources) Help
Ecology & Life History
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Basic Description: A fish (trout).
General Description: Resident adults are 15-30 cm in length whereas migratory adults commonly exceed 60 cm (see Rieman and McIntyre 1993).
Reproduction Comments: Spawns in late summer or fall, with falling temperatures between 5 C and 9 C. Eggs hatch in late winter or early spring. Fry emerge from gravel in April or May. Most information indicates that sexual maturity is attained in 5-7 years (also reported as 4-5 years). May spawn each year or in alternate years. Spawning populations may comprise four or more year classes, though one or two year classes may dominate. See Rieman and McIntyre (1993).
Ecology Comments: Resident and migratory form live together but whether they represent a single population or separate populations is unknown (Rieman and McIntyre 1993).

Vigorous populations may require abundant fish forage (Rieman and McIntyre 1993).

Available information indicates that bull trout and other native fishes use different resources, reducing direct competition (Rieman and McIntyre 1993).

Habitat Type: Freshwater
Non-Migrant: Y
Locally Migrant: Y
Long Distance Migrant: N
Mobility and Migration Comments: Two distinct forms, resident and migratory, exist throughout the range (Rieman and McIntyre 1993). Migratory form migrates between spawning and nonspawning habitats; migrates upstream to spawning areas in spring. Anadromy has not been documented but may have been important in the past (see Rieman and McIntyre 1993).
Riverine Habitat(s): BIG RIVER, CREEK, High gradient, Low gradient, MEDIUM RIVER, Moderate gradient, Pool, Riffle
Lacustrine Habitat(s): Deep water, Shallow water
Special Habitat Factors: Benthic
Habitat Comments: Habitat includes the bottom of deep pools in cold rivers and large tributary streams, often in moderate to fast currents with temperatures of 45-50 F; also large coldwater lakes and reservoirs. In the contiguous U.S., now extirpated in most large rivers that historically were inhabited; confined mostly to headwater streams. Conditions that favor the persistence of populations include stable channel, relatively stable stream flow, low levels of fine substrate sediments, high stream channel complexity with various cover types, temperatures not exceeding about 15 C, and the presence of suitable corridors for movement between suitable winter and summer habitats and for genetic exchange among populations (Rieman and McIntyre 1993).

Migratory forms live in tributary streams for up to several years before migrating downstream into a larger river or lake, where they spend several years before returning to tributaries to spawn (Rieman and McIntyre 1993). Some or most juveniles move to larger rivers or to a lake by mid-summer, while others stay in spawning areas for 2-4 years (Spahr et al. 1991). Adults return to river or lake after spawning in small streams. May move to lower reaches of mainstream river for winter. Resident populations often occur in small headwater streams where they spend their entire lives (see Rieman and McIntyre 1993). In lakes, inhabits all depths in fall, winter, and spring; moves to cooler, deeper water for summer.

Spawning usually occurs in gravel riffles of small tributary streams, including lake inlet streams. Spawning sites often are associated with springs (Rieman and McIntyre 1993). According to California Department of Fish and Game (1990), spawning requires a large volume of cold water. Optimum temperatures for incubation are about 2-4 C (see Rieman and McIntyre 1993). Constructs spawning redd. Young are closely associated with stream channel substrates (Rieman and McIntyre 1993). Areas with large woody debris and rubble substrate are important as juvenile rearing habitat (Spahr et al. 1991).

Adult Food Habits: Carnivore, Invertivore, Piscivore
Immature Food Habits: Carnivore, Invertivore, Piscivore
Food Comments: Eats terrestrial and aquatic insects, macrozooplankton, mysids, and fishes. Young feed heavily on aquatic insects. Adults feed principally on fishes, but have also been known to eat other small vertebrates, including frogs, snakes, mice, ducklings, etc. (Moyle 1976).
Length: 90 centimeters
Economic Attributes Not yet assessed
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Management Summary
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Management Requirements: Management efforts should include (1) habitat improvement such as the creation of instream structures that provide pockets of slow water favorable to juveniles and (2) protection from introduced brook trout (Spahr et al. 1991). See Thomas et al. (1993) for information on habitat management for this and other at-risk fish species in the Pacific Northwest.

Based on reproduction by F1 hybrids, Kanda et al. (2002) concluded that it would be appropriate to remove brook trout and brook trout/bull trout hybrids from streams occupied by bull trout.

A draft recovery plan for three of the five distinct population segments (Klamath, Columbia, and St. Mary-Belly Rivers) was available in late November 2002 (http://pacific.fws.gov). Recovery will require reducing threats to long-term population persistence, maintaining multiple interconnected populations across diverse habitats, and preserving the diversity of life-history strategies (e.g., resident or migratory forms, emigration age, spawning frequency, local habitat adaptations). See the draft recovery plan for further details.

Rieman and Allendorf (2001) concluded that cautious long-term management goals for bull trout populations should include an average of at least 1,000 adults spawning each year. Where local populations are too small, managers should seek to conserved a collection of interconnected populations that is at least large enough in total to meet this minimum (Rieman and Allendorf 2001). Also, full expression of life history variation and the natural processes of dispersal and gene flow should be provided (Rieman and Allendorf 2001).

Monitoring Requirements: Trends in habitat conditions and bull trout abundance should be identified and assessed (Rieman and McIntyre 1993). Top priority should be given to areas with the greatest threats.

Monitoring only a few index populations may not clearly represent the dynamics of larger regional populations (Rieman and McIntyre 1996, Dunham et al. 2001). Using redd counts to detect population trends will often require 10 or more years of sampling (Rieman and Myers 1997).

Dunham et al. (2001) found that substantial improvements are needed to make redd counts (subject to a large amount or error) and unbiased estimates of adult escapement more useful for population monitoring.

See Thurow and Schill (1996) for information on methods (day and night snorkeling, electrofishing) for estimating abundance and size structure.

Management Research Needs: Rieman and McIntyre (1993) listed the following research priorities: determine the range of conditions (especially temperature) tolerated by stable populations; determine the role of habitat disruption in the displacement of bull trout by brook trout; determine the effects of constructing barriers to limit the expansion of brook trout; investigate metapopulation structure and dynamics and dispersal; investigate the role of environmental variation in local extinction risk; investigate the role of the resident and migratory forms in population persistence, and determine the interactions between these forms; explore simulation methods for estimating extinction risks.
Population/Occurrence Delineation
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Group Name: Nonanadromous Salmonids

Use Class: Not applicable
Subtype(s): Spawning Area
Minimum Criteria for an Occurrence: Occurrences are based on evidence of historical presence, or current and likely recurring presence, at a given location. Such evidence minimally includes collection or reliable observation and documentation of one or more individuals (including eggs and larvae) in appropriate habitat.
Mapping Guidance: Conceptually, the occurrence includes the entire area used by the population, including spawning, rearing, migration, and wintering areas. Occupied locations that are separated by a gap of 10 km or more of any aquatic habitat that is not known to be occupied represent different occurrences. However, it is important to evaluate migrations and seasonal changes in habitat (see separation justification) to ensure that spawning areas and nonspawning areas for a single population are not artificially segregated as different occurrences simply because there have been no collections/observations in an intervening area that may exceed the separation distance.
Separation Barriers: Dam lacking a suitable fishway; high waterfall; upland habitat.
Alternate Separation Procedure: Separation distance is 10 stream-km for both suitable and unsuitable habitat. However, if it is known that the same population occupies sites separated by more than 10 km (e.g., this may be common for migratory populations), those sites should be included within the same occurrence. In lakes, occurrences include all suitable habitat that is presumed to be occupied (based on expert judgment), even if documented collection/observation points are more than 10 km apart. Separate sub-occurrences or source features may usefully document locations of critical spawning areas within a lake.

Separation Justification: Separation distance is arbitrary; little is known about juvenile dispersal (e.g., how far fishes may move between between their embryonic developmental habitat and eventual spawning site). "Restricted movement is the norm in populations of stream salmonids during nonmigratory periods," but there is considerable variation in movements within and among species (Rodriguez 2002).

Migrations can be extensive. For example, in the Kennebecasis River, New Brunswick, brook trout moved upstream 65-100 km in spring after ice loss; summer movements were minimal; movements to spawning areas in fall were less than 10 km, then the fish moved back downstream to wintering areas in the lower to middle reaches of the river (Curry et al. 2002).

Because of the difficulty in defining suitable versus unsuitable habitat, especially with respect to dispersal, and to simplify the delineation of occurrences, a single separation distance is used regardless of habitat quality.

Date: 11Mar2003
Author: Hammerson, G.
Population/Occurrence Viability
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U.S. Invasive Species Impact Rank (I-Rank) Not yet assessed
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Authors/Contributors
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NatureServe Conservation Status Factors Edition Date: 14Dec2011
NatureServe Conservation Status Factors Author: Hammerson, G., and D. Genter
Management Information Edition Date: 19Mar2003
Element Ecology & Life History Edition Date: 04Nov2011
Element Ecology & Life History Author(s): Hammerson, G.

Zoological data developed by NatureServe and its network of natural heritage programs (see Local Programs) and other contributors and cooperators (see Sources).

References
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  • Brown, C. J. D. 1971. Fishes of Montana. Big Sky Books, the Endowment and Research Foundation, Montana State University, Bozeman. MT. 207 pp.

  • California Department of Fish and Game (CDF&G). 1990. 1989 annual report on the status of California's state listed threatened and endangered plants and animals. 188 pp.

  • Cavender, T. M. 1978. Taxonomy and distribution of the bull trout, Salvelinus confluentus (Suckley), from the American Northwest. California Fish and Game 64:139-174.

  • Costello, A. B., T. E. Down, S. M. Pollard, C. J. Pacas, and E. B. Taylor. 2003. The influence of history and contemporary stream hydrology on the evolution of genetic diversity within species: an examination of microsatellite DNA variation in bull trout, Salvelinus confluentus (Pisces: Salmonidae). Evolution 57:328-344.

  • Donald, D. B., and D. J. Alger. 1993. Geographic distribution, species displacement, and niche overlap for lake trout and bull trout in mountain lakes. Canadian Journal of Zoology 71:238-247.

  • Dunham, J., B. Rieman, and K. Davis. 2001. Sources and magnitude of sampling error in redd counts for bull trout. North American Journal of Fisheries Management 21:343-352.

  • Fraley, J. J., and B. B. Shepard. 1989. Life history, ecology and population status of migratory bull trout (Salvelinus confluentus) in the Flathead Lake and River System, Montana. Northwest Science 63(4):133-14X.

  • Haas, G. R., and J. D. McPhail. 1991. Systematics and distribution of the Dolly Varden (Salvelinus malma) and bull trout (Salvelinus confluentus) in North America. Canadian Journal of Fisheries and Aquatic Sciences 48:2191-2211.

  • Hagen, J., and S. Decker. 2011. The status of bull trout in British Columbia: a synthesis of available distribution, abundance, trend, and threat information. Report prepared for: Ministry of Environment, Ecosystems Protection & Sustainability Branch, Aquatic Conservation Science Section, Victoria, British Columbia.

  • Howell, P. J., and D. V. Buchanan, editors. 1992. Proceedings of the Gearhart Mountain bull trout workshop. Oregon Chapter of the American Fisheries Society, Corvallis.

  • Kanda, N., R. F. Leary, and F. W. Allendorf. 2002. Evidence of introgressive hybridization between bull trout and brook trout. Transactions of the American Fisheries Society 131:772-782.

  • Leary, R. F., F. W. Allendorf, and S. H. Forbes. 1993. Consevation genetics of bull trout in the Columbia and Klamath river drainages. Conservation Biology 7:856-865.

  • Lee, D. S., C. R. Gilbert, C. H. Hocutt, R. E. Jenkins, D. E. McAllister, and J. R. Stauffer, Jr. 1980. Atlas of North American freshwater fishes. North Carolina State Museum of Natural History, Raleigh, North Carolina. i-x + 854 pp.

  • McMichael, G. A., and T. N. Pearsons. 2001. Upstream movement of residual hatchery steelhead into areas containing bull trout and cutthroat trout. North American Journal of Fisheries Management 21:943-946.

  • McPhail, J. D. 1961. A systematic study of the Salvelinus alpinus complex in North America. Journal of the Fisheries Research Board of Canada 18(5):793-816.

  • Minckley, W. L., and J. E. Deacon. 1991. Battle Against Extinction: Native Fish Management in the American West. University of Arizona Press, Tucson. xviii + 517 pp.

  • Moyle, P. B. 1976a. Inland fishes of California. University of California Press, Berkeley, California. 405 pp.

  • Moyle, P. B. 2002. Inland fishes of California. Revised and expanded. University of California Press, Berkeley. xv + 502 pp.

  • Nelson, J. S., E. J. Crossman, H. Espinosa-Perez, L. T. Findley, C. R. Gilbert, R. N. Lea, and J. D. Williams. 2004. Common and scientific names of fishes from the United States, Canada, and Mexico. American Fisheries Society, Special Publication 29, Bethesda, Maryland. 386 pp.

  • Page, L. M., H. Espinosa-Pérez, L. T. Findley, C. R. Gilbert, R. N. Lea, N. E. Mandrak, R. L. Mayden, and J. S. Nelson. 2013. Common and scientific names of fishes from the United States, Canada, and Mexico. Seventh edition. American Fisheries Society, Special Publication 34, Bethesda, Maryland.

  • Page, L. M., and B. M. Burr. 1991. A field guide to freshwater fishes: North America north of Mexico. Houghton Mifflin Company, Boston, Massachusetts. 432 pp.

  • Page, L. M., and B. M. Burr. 2011. Peterson field guide to freshwater fishes of North America north of Mexico. Second edition. Houghton Mifflin Harcourt, Boston. xix + 663 pp.

  • Platts, W. S., M. Hill, T. W. Hillman, and M. D. Miller. 1993. Preliminary status report on bull trout in California, Idaho, Montana, Nevada, Oregon, and Washington. Intermountain Forest Industry Association, Coeur d'Alene, Idaho.

  • Redenbach, Z., and E. B. Taylor. 2002. Evidence for historical introgression along a contact zone between two species of char (Pisces: Salmonidae) in northwestern North America. Evolution 56:1021-1035.

  • Rieman, B. E., and D. L. Myers. 1997. Use of redd counts to detect trends in bull trout (Salvelinus confluentus) populations. Conservation Biology 11:1015-1018.

  • Rieman, B. E., and F. W. Allendorf. 2001. Effective population size and genetic conservation criteria for bull trout. North American Journal of Fisheries Management 21:756-764.

  • Rieman, B. E., and J. D. McIntyre. 1993. Demographic and habitat requirements for conservation of bull trout. USDA Forest Service, Intermountain Research Station, Gen. Tech. Rep. INT-302. 38 pp.

  • Rieman, B. E., and J. D. McIntyre. 1996. Spatial and temporal variability in bull trout redd counts. North American Journal of Fisheries Management 16:132-141.

  • Robins, C.R., R.M. Bailey, C.E. Bond, J.R. Brooker, E.A. Lachner, R.N. Lea, and W.B. Scott. 1991. Common and scientific names of fishes from the United States and Canada. American Fisheries Society, Special Publication 20. 183 pp.

  • Rodriguez, M. A. 2002. Restricted movement in stream fish: the paradigm is complete, not lost. Ecology 83(1):1-13.

  • Scott, W. B., and E. J. Crossman. 1973. Freshwater fishes of Canada. Fisheries Research Board of Canada, Bulletin 184. 966 pp.

  • Simpson, J. and R. Wallace. 1982. Fishes of Idaho. The University Press of Idaho, Moscow, Idaho. 238 pp.

  • Spahr, R., L. Armstrong, D. Atwood, and M. Rath. 1991. Threatened, endangered, and sensitive species of the Intermountain Region. U.S. Forest Service, Ogden, Utah.

  • Starnes, W. C. 1995. Taxonomic validation for fish species on the U.S. Fish and Wildlife Service Category 2 species list. 28 pp.

  • Stoltz, J., and J. Schnell (eds.). 1991. Trout: The Wildlife Series. Stackpole Books, Harrisburg, Pennsylvania. 384 pp.

  • Thomas, G. 1992. Status of bull trout in Montana. Report prepared for Montana Department of Fish, Wildlife and Parks, Helena, Montana.

  • Thomas, J. W., Ward, J., Raphael, M.G., Anthony, R.G., Forsman, E.D., Gunderson, A.G., Holthausen, R.S., Marcot, B.G., Reeves, G.H., Sedell, J.R. and Solis, D.M. 1993. Viability assessments and management considerations for species associated with late-successional and old-growth forests of the Pacific Northwest. The report of the Scientific Analysis Team. USDA Forest Service, Spotted Owl EIS Team, Portland Oregon. 530 pp.

  • Thurow, R. F., and D. J. Schill. 1996. Comparison of day snorkeling, night snorkeling, and electrofishing to estimate bull trout abundance and size structure in a second-order Idaho stream. North American Journal of Fisheries Management 16:314-323.

  • U.S. Fish and Wildlife Service (USFWS). 1 November 1999. Determination of threatened status for bull trout in the coterminous United States. Federal Register 64(210):58910-58933.

  • U.S. Fish and Wildlife Service (USFWS). 10 June 1998. Determination of threatened status for the Klamath River and Columbia River distinct population segments of bull trout. Federal Register 63(111):31647-31674.

  • U.S. Fish and Wildlife Service (USFWS). 10 June 1998. Proposal to list the coastal-Puget Sound, Jarbridge River and St. Mary-Belly River population segments of bull trout as threatened species. Federal Register 63(111):31693-31710.

  • U.S. Fish and Wildlife Service (USFWS). 13 June 1997. Proposal to list the Klamath River population segment of bull trout as an endangered species and Columbia River population segment of bull trout as a threatened species. Federal Register 62:32268-32284.

  • U.S. Fish and Wildlife Service (USFWS). 2010. Endangered and threatened wildlife and plants; establishment of a nonessential experimental population of bull trout in the Clackamas River subbasin, Oregon. Federal Register 74(235):65045-65056.

  • U.S. Fish and Wildlife Service (USFWS). 2011. Endangered and threatened wildlife and plants; establishment of a nonessential experimental population of bull trout in the Clackamas River subbasin, Oregon. Federal Register 76(119):35979-35995.

  • U.S. Fish and Wildlife Service (USFWS). 29 November 2002. Proposed designation of critical habitat for the Klamath River and Columbia River distinct population segments of bull trout. Federal Register 67(230):71236-71438.

  • U.S. Fish and Wildlife Service (USFWS). 8 April 1999. Determination of threatened status for the Jarbridge River population segment of bull trout. Federal Register 64(67):17110-17125.

  • Zydlewski, G. B., and J. R. Johnson. 2002. Response of bull trout fry to four types of water diversion screens. North American Journal of Fisheries Management 22:1276-1282.

References for Watershed Distribution Map
  • Master, L. L. 1996. Synoptic national assessment of comparative risks to biological diversity and landscape types: species distributions. Summary Progress Report submitted to Environmental Protection Agency. The Nature Conservancy, Arlington, Virginia. 60 pp.

  • Master, L. L. and A. L. Stock. 1998. Synoptic national assessment of comparative risks to biological diversity and landscape types: species distributions. Summary Report submitted to Environmental Protection Agency. The Nature Conservancy, Arlington, VA. 36 pp.

  • State Natural Heritage Data Centers. 1996a. Aggregated element occurrence data from all U.S. state natural heritage programs, including the Tennessee Valley Authority, Navajo Nation and the District of Columbia. Science Division, The Nature Conservancy.

  • State Natural Heritage Data Centers. 1996b. Aggregated element occurrence data from all U.S. state natural heritage programs, including the Tennessee Valley Authority, Navajo Nation and the District of Columbia: Export of freshwater fish and mussel records west of the Mississippi River in 1997. Science Division, The Nature Conservancy.

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