Oncorhynchus tshawytscha - (Walbaum, 1792)
Chinook Salmon
Other English Common Names: King Salmon
Taxonomic Status: Accepted
Related ITIS Name(s): Oncorhynchus tshawytscha (Walbaum in Artedi, 1792) (TSN 161980)
French Common Names: saumon chinook
Unique Identifier: ELEMENT_GLOBAL.2.102499
Element Code: AFCHA02050
Informal Taxonomy: Animals, Vertebrates - Fishes - Bony Fishes - Salmon and Trouts
 
Kingdom Phylum Class Order Family Genus
Animalia Craniata Actinopterygii Salmoniformes Salmonidae Oncorhynchus
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: Oncorhynchus tshawytscha
Taxonomic Comments: See Utter et al. (1989) for information on genetic differences among populations in the Pacific Northwest. In the Nanaimo River, British Columbia, within-stock variation in age of seaward migration of juveniles is a genetic adaptation to local rearing environments; fishes with different life histories had biochemical and morphological differences that were linked to increased fitness in different rearing habitats (see Nehlsen et al. 1991). Waples and Teel (1990) found substantial allele frequency changes over 2-4 years in hatchery, but not wild, populations along the Pacific coast of Oregon.

Has hybridized with pink salmon in the St. Marys River, Michigan (Rosenfield 1998).
Conservation Status
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NatureServe Status

Global Status: G5
Global Status Last Reviewed: 28Dec2017
Global Status Last Changed: 08Mar1996
Ranking Methodology Used: Ranked by inspection
Rounded Global Status: G5 - Secure
Reasons: Still widespread and locally numerous in large range in the North Pacific Ocean and associated streams; many stocks have been extirpated and many others have declined; habitat has been degraded by logging and other activities, and dams have impeded movements; releases of hatchery stock probably have masked declines/extirpations of some native stocks; see separate files for various chinook salmon populations.
Nation: United States
National Status: N4 (22Nov2000)
Nation: Canada
National Status: N4N5B,N5N,N5M (28Dec2017)

U.S. & Canada State/Province Status
Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
United States Alaska (S4), California (SNR), Idaho (SNA), Illinois (SNA), Indiana (SNA), Maine (SNA), Michigan (SNA), Montana (SNA), Nevada (SX), New York (SNA), North Dakota (SNA), Oregon (S4?), Pennsylvania (SNA), South Dakota (SNA), Washington (S3S4), Wisconsin (SNA)
Canada British Columbia (S4), Nova Scotia (SNA), Nunavut (SUB,SNRN,SNRM), Ontario (SNA), Quebec (SNA), Yukon Territory (S2S3B)

Other Statuses

Implied Status under the U.S. Endangered Species Act (USESA): PS
Comments on USESA: Sacramento River winter run and Upper Columbia River spring run populations are listed as Endangered under the U.S. Endangered Species Act; Snake River spring/summer run, Snake River fall run, Puget Sound, Lower Columbia River, Upper Willamette River (spring run), and California coastal populations are listed as Threatened; Central Valley fall and late fall runs are species of concern. In a 90-day petition finding, NMFS (2015) found delisting the Snake River fall-run may be warranted and have initiated a status review.

FWS has proposed to designate the release of a nonessential experimental population in part of the Upper Columbia River Spring Run, found in the mainstem or tributaries of the Okanogan River from the Canada-United States border to the confluence of the Okanogan River with the Columbia River, Washington. NMFS (2013) has designated a nonessential experimental population of Central Valley spring-run Chinook salmon in portions of the San Joaquin River Valley, California (Federal Register, 31 December 2013).

In a 90-day finding on a petition to list the Upper Klamath-Trinity Rivers (UKTR) Chinook salmon ESU or, alternatively, create a new ESU to describe Klamath Spring Chinook salmon and list the new ESU as threatened or endangered, NMFS (2018) find that the petition may be warranted.

Implied Status under the Committee on the Status of Endangered Wildlife in Canada (COSEWIC):PS:E
Comments on COSEWIC: Okanagan population is designated Endangered.

NatureServe Global Conservation Status Factors

Range Extent Comments: Native range includes the Pacific Ocean and tributary drainages, in North America presently from the Sacramento-San Joaquin system (sometimes farther south) north to Point Hope, Alaska, and in northeastern Asia, from northern Japan to the Anadyr River. The species has been widely stocked elsewhere.

In the Columbia River basin, the Hanford Reach supports the largest population of fall chinook salmon; annual production is an estimated 20-25 million subyearling salmon (P. Hoffarth, Washington Department of Fish and Wildlife, unpublished data).

Number of Occurrences:  
Number of Occurrences Comments: In a survey of populations in the contiguous U.S., Huntington et al. (1996) identified 32 healthy native stocks of fall chinook, all in Washington and Oregon, and 3 healthy native stocks of spring or summer chinook, all in Washington.

Population Size Comments: Least abundant of Pacific salmon (Lee et al. 1980).

Overall Threat Impact Comments: Initial cause of decline was adverse effects of logging, mining, irrigation withdrawals, and overfishing, then construction of hydroelectric dams blocked migrations and resulted in high mortality of smolts in turbines (Nehlsen et al. 1991, Williams et al. 1992). Spawning runs continue to be threatened by construction of dams and degradation of natural environment. Extinctions or large declines of some local native populations in recent decades may have been masked by releases of non-native hatchery stock (Williams et al. 1992).

Juveniles incur high mortality as they migrate through today's river systems and out to sea. Sources of mortality include hydroelectric turbines, mechanical bypass facilities (including transportation by barge or truck), and predation by non-native fishes. Gas bubble trauma (GBT)associated with total dissolved gas supersaturation (TDGS) at spillways also causes mortality and detrimental sublethal effects, but passage of juveniles through spillways may be the least damaging of the routes for juvenile passage at dams (Backman et al. 2002). In the Columbia River basin, adults were rarely observed with GBT, despite high TDGS levels (Backman and Evans 2002).

Concurrent with the construction of fish hatcheries, bacterial kidney disease became prevalent and may now play a significant role in mortality.

A change in climate, beginning around 1977, led to poor ocean survival.

See also threats comments for individual populations (ESUs).

Short-term Trend: Decline of 10-30%
Short-term Trend Comments: At least 50 stocks have been extirpated; see Nehlsen et al. (1991) for a review of the status of various at-risk/special concern populations from California, the Oregon coast, the Columbia River basin, and Puget Sound. Of 866 stocks in British Columbia and Yukon, Slaney et al. (1996) categorized 17 as extirpated, 47 as high risk, 6 as moderate risk, 7 as special concern, 330 as unthreatened, and 459 as unknown status. Regarding spring runs outside the Sacramento-San Joaquin population: the run in Salmon River drainage (North and South forks, and Wooley Creek, California) apparently was stable at 1000-1500 adults in the 1980s; the flood of 1964 reduced available habitat for population in the South Fork of the Trinity River, and the population there now is much smaller than previously; most individuals in the Klamath-Trinity drainage are derived from hatchery stock. Ratner et al. (1997) conducted a population viability analysis of spring chinook salmon in the South Umpqua River, Oregon (this is part of the Oregon Coast ESU) and found a 95% probability of persistence of 200 years with no further habitat destruction; with continued habitat destruction, the population was projected to be almost certainly extirpated within 100 years.

Other NatureServe Conservation Status Information

Protection Needs: Meffe (1992) gave reasons why the hatchery approach to recovery ultimately will fail, and he emphasized that overharvest and habitat destruction need to be addressed in a major landscape-level effort. See Nehlsen et al. (1991) for general protection recommendations for anadromous salmonids. See recovery plan for Sacramento-San Joaquin Delta native fishes (USFWS 1995).

Distribution
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Global Range: Native range includes the Pacific Ocean and tributary drainages, in North America presently from the Sacramento-San Joaquin system (sometimes farther south) north to Point Hope, Alaska, and in northeastern Asia, from northern Japan to the Anadyr River. The species has been widely stocked elsewhere.

In the Columbia River basin, the Hanford Reach supports the largest population of fall chinook salmon; annual production is an estimated 20-25 million subyearling salmon (P. Hoffarth, Washington Department of Fish and Wildlife, unpublished data).

U.S. States and Canadian Provinces

Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
Color legend for Distribution Map
Endemism: occurs (regularly, as a native taxon) in multiple nations

U.S. & Canada State/Province Distribution
United States AK, CA, ID, ILexotic, INexotic, MEexotic, MIexotic, MTexotic, NDexotic, NVextirpated, NYexotic, OR, PAexotic, SDexotic, WA, WIexotic
Canada BCnative and exotic, NSexotic, NU, ONexotic, QCexotic, YT

Range Map
No map available.


U.S. Distribution by County Help
State County Name (FIPS Code)
AK Skagway-Hoonah-Angoon (CA) (02232)
CA Butte (06007), Humboldt (06023), Nevada (06057), Shasta (06089), Siskiyou (06093), Sutter (06101), Tehama (06103), Trinity (06105), Yolo (06113), Yuba (06115)
NV Elko (32007)*
OR Benton (41003), Clackamas (41005), Clatsop (41007), Columbia (41009), Coos (41011), Curry (41015), Douglas (41019), Gilliam (41021), Grant (41023), Hood River (41027), Jackson (41029), Jefferson (41031), Josephine (41033), Lane (41039), Lincoln (41041), Linn (41043), Marion (41047), Morrow (41049), Multnomah (41051), Polk (41053), Sherman (41055), Tillamook (41057), Umatilla (41059), Union (41061), Wallowa (41063), Wasco (41065), Washington (41067), Wheeler (41069), Yamhill (41071)
WA Asotin (53003)+, Benton (53005)+, Chelan (53007)+, Clallam (53009)+, Clark (53011)+, Columbia (53013)+, Cowlitz (53015)+, Douglas (53017)+, Franklin (53021)+, Garfield (53023)+, Grant (53025)+, Grays Harbor (53027)+, Jefferson (53031)+, King (53033)+, Kittitas (53037)+, Klickitat (53039)+, Lewis (53041)+, Mason (53045)+, Okanogan (53047)+, Pacific (53049)+, Pierce (53053)+, Skagit (53057)+, Skamania (53059)+, Snohomish (53061)+, Thurston (53067)+, Wahkiakum (53069)+, Walla Walla (53071)+, Whatcom (53073)+, Whitman (53075)+, Yakima (53077)+
* Extirpated/possibly extirpated
U.S. Distribution by Watershed Help
Watershed Region Help Watershed Name (Watershed Code)
17 Kettle (17020002), Chief Joseph (17020005), Okanogan (17020006), Similkameen (17020007), Methow (17020008), Lake Chelan (17020009), Upper Columbia-Entiat (17020010), Wenatchee (17020011), Moses Coulee (17020012), Upper Columbia-Priest Rapids (17020016), Upper Yakima (17030001), Naches (17030002), Lower Yakima, Washington (17030003), Bruneau (17050102)+*, Middle Snake-Succor (17050103)*, South Fork Owyhee (17050105)+*, Middle Owyhee (17050107)*, Jordan (17050108)*, Lower Owyhee (17050110)*, Middle Snake-Payette (17050115)*, Brownlee Reservoir (17050201)*, Hells Canyon (17060101)+, Imnaha (17060102)+, Lower Snake-Asotin (17060103)+, Upper Grande Ronde (17060104)+, Wallowa (17060105)+, Lower Grande Ronde (17060106)+, Lower Snake-Tucannon (17060107), Lower Snake (17060110), Middle Columbia-Lake Wallula (17070101)+, Walla Walla (17070102), Umatilla (17070103), Willow (17070104), 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)+, Lower Crooked (17070305), Lower Deschutes (17070306)+, Trout (17070307), Lower Columbia-Sandy (17080001)+, Lewis (17080002), Lower Columbia-Clatskanie (17080003)+, Upper Cowlitz (17080004), Lower Cowlitz (17080005), Lower Columbia (17080006)+, Middle Fork Willamette (17090001)+, Coast Fork Willamette (17090002)+, Upper Willamette (17090003)+, Mckenzie (17090004)+, North Santiam (17090005)+, South Santiam (17090006)+, Middle Willamette (17090007)+, Yamhill (17090008)+, Molalla-Pudding (17090009)+, Tualatin (17090010), Clackamas (17090011)+, Lower Willamette (17090012)+, Hoh-Quillayute (17100101), Queets-Quinault (17100102), Upper Chehalis (17100103), Lower Chehalis (17100104), Grays Harbor (17100105), Willapa Bay (17100106), Necanicum (17100201), Nehalem (17100202), Wilson-Trusk-Nestuccu (17100203)+, Siletz-Yaquina (17100204)+, Alsea (17100205)+, Siuslaw (17100206), Siltcoos (17100207), North Umpqua (17100301)+, South Umpqua (17100302)+, Umpqua (17100303)+, Coos (17100304), Coquille (17100305)+, Sixes (17100306)+, Upper Rogue (17100307)+, Middle Rogue (17100308)+, Applegate (17100309)+, Lower Rogue (17100310)+, Illinois (17100311)+, Chetco (17100312)+, 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), Crescent-Hoko (17110021)
18 Smith (18010101)+, Mad-Redwood (18010102), Upper Eel (18010103), Middle Fork Eel (18010104), Lower Eel (18010105)+, South Fork Eel (18010106), Mattole (18010107), Big-Navarro-Garcia (18010108), Gualala-Salmon (18010109), Russian (18010110), Upper Klamath (18010206)+, Shasta (18010207), Scott (18010208), Lower Klamath (18010209)+, Salmon (18010210)+, Trinity (18010211)+, South Fork Trinity (18010212)+, Lower Pit (18020003)*, Mccloud (18020004)*, Sacramento headwaters (18020005)*, Sacramento-Lower Cow-Lower Clear (18020101), Lower Cottonwood (18020102), Sacramento-Lower Thomes (18020103), Sacramento-Stone Corral (18020104)+, Lower Butte (18020105), Lower Feather (18020106), Lower Yuba (18020107), Lower Bear (18020108), Lower Sacramento (18020109), Lower Cache (18020110)*, Lower American (18020111), Cottonwood headwaters (18020113), Upper Elder-Upper Thomes (18020114), Upper Stony (18020115)*, Upper Putah (18020117)*, Upper Cow-Battle (18020118)*, Mill-Big Chico (18020119), Upper Butte (18020120), North Fork Feather (18020121), Middle Fork Feather (18020123), Honcut headwaters (18020124), Upper Yuba (18020125)+, Upper Bear (18020126)+, Upper Coon-Upper Auburn (18020127), North Fork American (18020128), South Fork American (18020129), Cow Creek (18020151)+, Cottonwood Creek (18020152)+, Battle Creek (18020153)+, Clear Creek-Sacramento River (18020154)+, Paynes Creek-Sacramento River (18020155)+, Thomes Creek-Sacramento River (18020156)+, Big Chico Creek-Sacramento River (18020157)+, Butte Creek (18020158)+, Honcut Headwaters-Lower Feather (18020159)+, Upper Coon-Upper Auburn (18020161)+, Lower Sacramento (18020163)+, Mill (18030008)*, Upper King (18030010)*, Tulare-Buena Vista Lakes (18030012)*, Middle San Joaquin-Lower (18040001)*, Middle San Joaquin-Lower (18040002), San Joaquin Delta (18040003), Lower Calaveras-Mormon Slough (18040004), Lower Cosumnes-Lower Mokelumne (18040005), Upper San Joaquin (18040006)*, Upper Chowchilla-Upper Fresno (18040007), Upper Merced (18040008), Upper Tuolumne (18040009), Upper Stanislaus (18040010), Upper Calaveras (18040011), Upper Mokelumne (18040012), Upper Cosumnes (18040013), Suisun Bay (18050001), San Pablo Bay (18050002), Coyote (18050003), San Francisco Bay (18050004), San Francisco Coastal South (18050006)
19 Admiralty Island (19010204)+
+ 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 large fish (salmon).
General Description: Numerous scales; one dorsal fin plus one adipose fin; no spines in fins; irregular black spots on back, both lobes of tail fin, dorsal fin, and adipose fin; gums black at base of teeth. In the ocean, chinook salmon are blue, green, or gray on the upper side, silvery-white on the flanks and belly. During the spawning season, chinook salmon are olive brown, red, or purplish, the color change being more pronounced in males than in females. Young have 6-12 large parr marks on each side. Total length to around 150 cm.
Diagnostic Characteristics: Differs from other Oncorhynchus by large size (to 45 kg), small black spots on both lobes of the caudal fin, black pigment along the base of the teeth, large number of pyloric caeca (>100), and variable flesh color (white to pink or red); fry and parr have large parr marks extending well below the lateral line (Healey 1991).
Reproduction Comments: Overall, chinook salmon generally spawn at 2-7 years of age (typically 3-5) in fall, depending on the population. A small proportion of males (called jacks) mature after only spending about 6 months or 18 months at sea, and still others mature without having migrated to sea at all. Eggs hatch in about 2-3 months and alevins complete development in another 1-2 months (depending on temperature, hence related to latitude and elevation). Juveniles stay in fresh water for a few days or 1 year (rarely more). Adults die soon after spawning. Several distinct spawning populations may occur in one stream; these may differ in duration of juvenile rearing, size and date of ocean entrance, timing of adult return and spawning, age composition of spawners, fecundity, and egg size (see Nehlsen et al. 1991).
Habitat Type: Freshwater
Non-Migrant: N
Locally Migrant: Y
Long Distance Migrant: Y
Mobility and Migration Comments: Anadromous; migrates up to several hundred km upstream to the stream in which they were spawned. Different races differ in the timing of adult migration and spawning. Oregon coastal chinook stocks vary in ocean migration; some stocks migrate north, some migrate south, and one stock has a mixed north and south migration (see Nehlsen et al. 1991). There are two basic behavioral forms, stream-type and ocean-type (see Salo 1991). Stream-type chinnok is typical of Asian populations and of northern populations and headwater tributaries of southern populations in North America; spends one or more years as fry or parr in fresh water before migrating to sea, performs extensive offshore oceanic migrations, returns to natal river in spring or summer, several months prior to spawning; occasionally males mature without ever going to sea. Ocean-type is typical of populations on the North American coast south of 56 degrees north latitude; migrates to sea during first year of life (normally within 3 months of emerging from spawning gravel), spends most of ocean life in coastal waters, return to natal river in fall, a few days or weeks before spawning.
Marine Habitat(s): Near shore, Pelagic
Estuarine Habitat(s): Bay/sound, River mouth/tidal river
Riverine Habitat(s): BIG RIVER, CREEK, Low gradient, MEDIUM RIVER, Moderate gradient, Pool, Riffle
Lacustrine Habitat(s): Deep water
Special Habitat Factors: Benthic
Habitat Comments: Chinook salmon generally spend most (often 2-4 years but up to 6 years) of their lives in the ocean. For spawning, they migrate up to several hundred kilometers upstream to their natal stream, where eggs are deposited in gravel bottoms of large streams and rivers.

Populations may differ dramatically in the timing of adult migration and, to a lesser extent, timing of spawning. There are two basic behavioral forms, stream-type and ocean-type. Stream-type chinook are typical of northern populations (i.e., Alaska and northern B.C.) and headwater (high elevation) tributaries of southern populations. These spend one full year as juveniles rearing in fresh water before migrating to sea, perform extensive offshore oceanic migrations, and typically return to their natal river in spring or summer, several months prior to spawning; occasionally males mature without ever going to sea. The ocean-type is typical of populations on the North American coast south of 56 degrees north latitude; these migrate to sea during their first year of life (normally within 3 months of emerging from spawning gravel), spend most of their ocean life in coastal waters, then return to their natal river in fall, a few weeks before spawning.

Adult Food Habits: Invertivore, Piscivore
Immature Food Habits: Invertivore, Piscivore
Food Comments: In fresh water juveniles feed opportunistically on terrestrial and aquatic insects. In salt water they eat crustaceans as well as other bottom invertebrates. Adults eat mostly fishes.
Length: 80 centimeters
Economic Attributes
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Economic Comments: Important both as a commercial and sport fish (Healey 1991). This species made up the majority of the Columbia River harvest in the late 1800s. The largest commercial catches have been along the coast of British Columbia, with sizable catches also south to California and north to Alaska. The fall run in the California portion of the Klamath River supports important ocean and river fisheries.
Management Summary
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Management Requirements: See Nehlsen et al. (1991) for general management recommendations for anadromous salmonids.

Allendorf et al. (1997) proposed criteria for prioritizing Pacific salmon stocks for conservation; data limitations introduce subjectivity into the process, so expert judgment and peer review should be incorporated into the process.

See Thomas et al. (1993) for information on habitat management for this and other at-risk fish species in the Pacific Northwest. Utter et al. (1989) recommended a conservative policy for stock transfers, based on distinct genetic differences among populations in different areas. See recovery plan for Sacramento-San Joaquin Delta native fishes (USFWS 1995).

Limiting flow fluctuations at all discharges below Priest Rapids Dam (Columbia River) would further protect subyearling fall chinook salmon (Tiffan et al. 2002). This would enhance production of invertebrate prey and reduce the stranding salmon on dewatered substrate or in disconnected pools.

Yearlings migrating downstream experience higher survival when spill is used specifically to pass fishes through nonturbine routes past hydroelectric dams (Muir et al. 2001).

Monitoring Requirements: Waples and Teel (1990) emphasized the importance of monitoring the genetic consequences of the large-scale artificial propagation programs involving Pacific salmon (see also Waples 1990).

Aerial photography can be used to monitor spawning of fall chinook salmon (Visser et al. 2002).

Population/Occurrence Delineation
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Group Name: Fishes with Anadromous Populations

Use Class: Freshwater
Subtype(s): Rearing & Migration Area, Spawning & Rearing 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. For anadromous populations, occurrences are based on collection or reliable observation and documentation of one or more spawning adults, redds, other evidence of spawning, or larvae or juveniles in appropriate spawning/rearing habitat.
Mapping Guidance: Conceptually, the occurrence includes the entire freshwater area used by the population, including spawning, rearing, and migration areas. For anadromous populations, an occurrence should extend from the most upstream spawning areas downstream to the ocean. However, it is desirable (and practical) to subdivide this sometimes very large occurrence, sometimes overlapping with many other spaghetti-like occurrences extending down from the upstream spawning areas to the ocean, into separate source features or sub-occurrences, labeled with a feature label that reflects the life history stage in that area. Moreover, it may make practical sense to treat the areas downstream of spawning and/or rearing areas as a mixed element animal assemblage: Freshwater Salmon Migration Corridor. This negates the need to separately map each occurrence down to the ocean from its upstream spawning location. Information about areas with different life-history uses can be generated by using best professional judgment by district or regional fish biologists and may or may not incorporate specific locational information from spawning surveys or other surveys.
Separation Barriers: Dam lacking a suitable fishway; high waterfall; upland habitat that is very unlikely to be submerged even during periods of exceptionally high water (e.g., 100-year flood or 1% flood).
Alternate Separation Procedure: For anadromous populations and migratory populations that have distinct and separate spawning and nonspawning areas, the area used by each population whose spawning area is separated by a gap of at least 10 stream-km from other spawning areas within a stream system is potentially mappable as a distinct occurrence that extends down to the ocean (but see mapping guidance), regardless of whether the spawning areas are in the same or different tributaries.

For other (e.g., nonanadromous) populations in streams, 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, nonanadromous 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: The separation distance is arbitrary but was selected to ensure that occurrences are of manageable size but not too small. 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.

"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). Redband trout in Montana had October-December home ranges of 5-377 m, consistent with small movements observed for radio-tagged brook trout and cutthroat trout during fall and winter (Muhlfeld et al. 2001). For nonanadromous populations, little is known about juvenile dispersal (e.g., how far fishes may move between between their embryonic developmental habitat and eventual spawning site).

In summer and fall, radio-tagged cutthroat trout in Strawberry Reservoir in Utah had single-month home ranges that were usually about 3-4 km in maximum length (Baldwin et al. 2002). In the Blackfoot River drainage, Montana, radio-tagged westslope cutthroat trout moved 3-72 km (mean 31 km) to access spawning tributaries (Schmetterling 2001). This indicates that migratory but nonanadromous populations may use extensive areas and that one should not invoke the 10-km separation distance without considering the full extent of the population.

Date: 25Nov2009
Author: Hammerson, G., and L. Master
Notes: This Specs Group comprises fish species that include anadromous populations (may also include nonanadromous populations), such as lampreys, sturgeons, herrings, shads, salmonids, and smelts.

Criteria for marine occurrences (Location Use Class: Marine) have not yet been established. These may not be needed for marine occurrences of species that likely will be dealt with as mixed element assemblages (e.g., Salmonid Marine Concentration Area).

Feature Descriptor Definitions:

Spawning Area: area used for spawning but not for rearing or migration.

Rearing Area: area used for larval/juvenile development but not for spawning or migration.

Migration Corridor: area used for migration but not for rearing or spawning.

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: 21Jan2010
NatureServe Conservation Status Factors Author: Hammerson, G.
Management Information Edition Date: 10Feb2003
Element Ecology & Life History Edition Date: 21Jan2010
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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  • Allendorf, F. W., D. Bayles, D. L. Bottom, K. P. Currens, C. A. Frissell, D. Hankin, J. A. Lichatowich, W. Nehlsen, P. C. Trotter, and T. H. Williams. 1997. Prioritizing Pacific salmon stocks for conservation. Conservation Biology 11:140-152.

  • Aquin, P. 1999. Évaluation de la situation des groupes taxonomiques des poissons du Québec. Ministère de l'Environnement et de la Faune. 9 pages.

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