54708 Federal Register / Vol. 75, No. 173 / Wednesday, September 8, 2010 / Proposed Rules 

DEPARTMENT OF THE INTERIOR 

Fish and Wildlife Service 

50 CFR Part 17 

[Docket No. FWS-R6-ES-2009-0065] 

[MO 92210-0-0008-B2] 

Endangered and Threatened Wildlife 

and Plants; Revised 12-Month Finding 

to List the Upper Missouri River 

Distinct Population Segment of Arctic 

Grayling as Endangered or Threatened 

AGENCY: Fish and Wildlife Service, 

Interior. 

ACTION: Notice of revised 12–month 

finding. 

SUMMARY: We, the U.S. Fish and 

Wildlife Service (Service/USFWS), 

announce a revised 12–month finding 

on a petition to list the upper Missouri 

River Distinct Population Segment 

(Missouri River DPS) of Arctic grayling 

(Thymallus arcticus) as endangered or 

threatened under the Endangered 

Species Act of 1973, as amended. After 

review of all available scientific and 

commercial information, we find that 

listing the upper Missouri River DPS of 

Arctic grayling as endangered or 

threatened is warranted. However, 

listing the upper Missouri River DPS of 

Arctic grayling is currently precluded 

by higher priority actions to amend the 

Lists of Endangered and Threatened 

Wildlife and Plants. Upon publication 

of this 12–month finding, we will add 

the upper Missouri River DPS of Arctic 

grayling to our candidate species list. 

We will develop a proposed rule to list 

this DPS as our priorities allow. We will 

make any determination on critical 

habitat during development of the 

proposed listing rule. In the interim, we 

will address the status of this DPS 

through our annual Candidate Notice of 

Review (CNOR). 

DATES: The finding announced in this 

document was made on September 8, 

2010. 

ADDRESSES: This finding is available on 

the Internet at http:// 

www.regulations.gov at Docket Number 

FWS-R6-ES-2009-0065. Supporting 

documentation we used in preparing 

this finding is available for public 

inspection, by appointment, during 

normal business hours at the U.S. Fish 

and Wildlife Service, Montana Field 

Office, 585 Shepard Way, Helena, MT 

59601. Please submit any new 

information, materials, comments, or 

questions concerning this finding to the 

above street address (Attention: Arctic 

grayling). 

FOR FURTHER INFORMATION CONTACT: 

Mark Wilson, Field Supervisor, 

Montana Field Office (see ADDRESSES); 

by telephone at 406-449-5225; or by 

facsimile at 406-449-5339. Persons who 

use a telecommunications device for the 

deaf (TDD) may call the Federal 

Information Relay Service (FIRS) at 800- 

877-8339. 

SUPPLEMENTARY INFORMATION: 

Background 

Section 4(b)(3)(B) of the Endangered 

Species Act of 1973, as amended (ESA) 

(16 U.S.C. 1531 et seq.), requires that, 

for any petition containing substantial 

scientific or commercial information 

indicating that listing the species may 

be warranted, we make a finding within 

12 months of the date of receipt of the 

petition. In this finding, we determine 

that the petitioned action is: (a) Not 

warranted, (b) warranted, or (c) 

warranted, but immediate proposal of a 

regulation implementing the petitioned 

action is precluded by other pending 

proposals to determine whether species 

are endangered or threatened, and 

expeditious progress is being made to 

add or remove qualified species from 

the Federal Lists of Endangered and 

Threatened Wildlife and Plants. Section 

4(b)(3)(C) of the ESA requires that we 

treat a petition for which the requested 

action is found to be warranted but 

precluded as though resubmitted on the 

date of such finding, that is, requiring a 

subsequent finding to be made within 

12 months. We must publish these 12– 

month findings in the Federal Register. 

Previous Federal Actions 

We have published a number of 

documents on Arctic grayling and have 

been involved in litigation over 

previous findings. We describe our 

actions relevant to this notice below. 

We initiated a status review for the 

Montana Arctic grayling (Thymallus 

arcticus montanus) in a Federal 

Register notice on December 30, 1982 

(47 FR 58454). In that notice, we 

designated the purported subspecies, 

Montana Arctic grayling, as a Category 

2 species. At that time, we designated a 

species as Category 2 if a listing as 

endangered or threatened was possibly 

appropriate, but we did not have 

sufficient data to support a proposed 

rule to list the species. 

On October 9, 1991, the Biodiversity 

Legal Foundation and George 

Wuerthner petitioned us to list the 

fluvial (riverine populations) of Arctic 

grayling in the upper Missouri River 

basin as an endangered species 

throughout its historical range in the 

coterminous United States. We 

published a notice of a 90–day finding 

in the January 19, 1993, Federal 

Register (58 FR 4975), concluding the 

petitioners presented substantial 

information indicating that listing the 

fluvial Arctic grayling of the upper 

Missouri River in Montana and 

northwestern Wyoming may be 

warranted. This finding noted that 

taxonomic recognition of the Montana 

Arctic grayling (Thymallus arcticus 

montanus) as a subspecies (previously 

designated as a category 2 species) was 

not widely accepted, and that the 

scientific community generally 

considered this population a 

geographically isolated member of the 

wider species (T. arcticus). 

On July 25, 1994, we published a 

notice of a 12–month finding in the 

Federal Register (59 FR 37738), 

concluding that listing the DPS of 

fluvial Arctic grayling in the upper 

Missouri River was warranted but 

precluded by other higher priority 

listing actions. This DPS determination 

predated our DPS policy (61 FR 4722, 

February 7, 1996), so the entity did not 

undergo a DPS analysis as described in 

the policy. The 1994 finding placed 

fluvial Arctic grayling of the upper 

Missouri River on the candidate list and 

assigned it a listing priority of 9. On 

May 4, 2004, we elevated the listing 

priority number of the fluvial Arctic 

grayling to 3 (69 FR 24881). 

On May 31, 2003, the Center for 

Biological Diversity and Western 

Watersheds Project (Plaintiffs) filed a 

complaint in U.S. District Court in 

Washington, D.C., challenging our 

‘‘warranted but precluded’’ 

determination for Montana fluvial 

Arctic grayling. On July 22, 2004, the 

Plaintiffs amended their complaint to 

challenge our failure to emergency list 

this population. We settled with the 

Plaintiffs in August 2005, and we agreed 

to submit a final determination on 

whether this population warranted 

listing as endangered or threatened to 

the Federal Register on or before April 

16, 2007. 

On April 24, 2007, we published a 

revised 12–month finding on the 

petition to list the upper Missouri River 

DPS of fluvial Arctic grayling (72 FR 

20305) (‘‘2007 finding’’). In this finding, 

we determined that fluvial Arctic 

grayling of the upper Missouri River did 

not constitute a species, subspecies, or 

DPS under the ESA. Therefore, we 

found that the upper Missouri River 

population of fluvial Arctic grayling was 

not a listable entity under the ESA, and 

as a result, listing was not warranted. 

With that notice, we withdrew the 

fluvial Arctic grayling from the 

candidate list. 


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On November 15, 2007, the Center for 

Biological Diversity, Federation of Fly 

Fishers, Western Watersheds Project, 

George Wuerthner, and Pat Munday 

filed a complaint (CV-07-152, in the 

District Court of Montana) to challenge 

our 2007 finding. We settled this 

litigation on October 5, 2009. In the 

stipulated settlement, we agreed to: (a) 

Publish, on or before December 31, 

2009, a notice in the Federal Register 

soliciting information on the status of 

the upper Missouri River Arctic 

grayling; and (b) submit, on or before 

August 30, 2010, a new 12–month 

finding for the upper Missouri River 

Arctic grayling to the Federal Register. 

On October 28, 2009, we published a 

notice of intent to conduct a status 

review of Arctic grayling (Thymallus 

arcticus) in the upper Missouri River 

system (74 FR 55524). To ensure the 

status review was based on the best 

available scientific and commercial 

data, we requested information on the 

taxonomy, biology, ecology, genetics, 

and population status of the Arctic 

grayling of the upper Missouri River 

system; information relevant to 

consideration of the potential DPS 

status of Arctic grayling of the upper 

Missouri River system; threats to the 

species; and conservation actions being 

implemented to reduce those threats in 

the upper Missouri River system. The 

notice further specified that the status 

review may consider various DPS 

designations that include different life 

histories of Arctic grayling in the upper 

Missouri River system. Specifically, we 

may consider DPS configurations that 

include: Fluvial, adfluvial (lake 

populations), or all life histories of 

Arctic grayling in the upper Missouri 

River system. 

This notice constitutes the revised 

12–month finding (‘‘2010 finding’’) on 

whether to list the upper Missouri River 

DPS of Arctic grayling (Thymallus 

arcticus) as endangered or threatened. 

Taxonomy and Species Description 

The Arctic grayling (Thymallus 

arcticus) belongs to the family 

Salmonidae (salmon, trout, charr, 

whitefishes), subfamily Thymallinae 

(graylings), and it is represented by a 

single genus, Thymallus. Scott and 

Crossman (1998, p. 301) recognize four 

species within the genus: T. articus 

(Arctic grayling), T. thymallus 

(European grayling), T. brevirostris 

(Mongolian grayling), and T. nigrescens 

(Lake Kosgol, Mongolia). Recent 

research focusing on Eurasian 

Thymallus (Koskinen et al. 2002, entire; 

Froufe et al. 2003, entire; Froufe et al. 

2005, entire; Weiss et al. 2006, entire) 

indicates that the systematic diversity of 

the genus is greater than previously 

thought, or at least needs better 

description (Knizhin et al. 2008, pp. 

725–726, 729; Knizhin and Weiss 2009, 

pp. 1, 7–8; Weiss et al. 2007, p. 384). 

Arctic grayling have elongate, 

laterally compressed, trout-like bodies 

with deeply forked tails, and adults 

typically average 300-380 millimeters 

(mm) (12-15 inches (in.)) in length. 

Coloration can be striking, and varies 

from silvery or iridescent blue and 

lavender, to dark blue (Behnke 2002, pp. 

327–328). The sides are marked with a 

varying number of V-shaped or 

diamond-shaped spots (Scott and 

Crossman 1998, p. 301). During the 

spawning period, the colors darken and 

the males become more brilliantly 

colored than the females. A prominent 

morphological feature of Arctic grayling 

is the sail-like dorsal fin, which is large 

and vividly colored with rows of orange 

to bright green spots, and often has an 

orange border (Behnke 2002, pp. 327– 

328). 

Distribution 

Arctic grayling are native to Arctic 

Ocean drainages of Alaska and 

northwestern Canada, as far east as 

Hudson’s Bay, and westward across 

northern Eurasia to the Ural Mountains 

(Scott and Crossman 1998, pp. 301–302; 

Froufe et al. 2005, pp. 106–107; Weiss 

et al. 2006, pp. 511–512; see Figure 1 

below). In North America, they are 

native to northern Pacific Ocean 

drainages as far south as the Stikine 

River in British Columbia (Nelson and 

Paetz 1991, pp. 253–256; Behnke 2002, 

pp. 327–331). 

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FIGURE 1. Approximate world-wide 

distribution of Arctic grayling 

(Thymallus arcticus) at the end of the 

most recent glacial cycle. The Missouri 

River distribution is based on Kaya 

(1992, pp. 47-51). The distribution of 

the extinct Michigan population is 

based on Vincent (1962, p. 12) and the 

University of Michigan (2010). The 

North American distribution in Canada 

and Alaska is based on Behnke (2002, p. 

330) and Scott and Crossman (1998, pp. 

301-302). The Eurasian distribution is 

based on Knizhin (2009, p. 32) and 

Knizhin (2010, pers. comm.). 

Arctic grayling remains widely 

distributed across its native range, but 

within North America, the species has 

experienced range decline or 

contraction at the southern limits of its 

distribution. In British Columbia, 

Canada, populations in the Williston 

River watershed are designated as a 

provincial ‘‘red list’’ species, meaning 

the population is a candidate for further 

evaluation to determine if it should be 

granted endangered (facing imminent 

extirpation or extinction) or threatened 

status (likely to become endangered) 

(British Columbia Conservation Data 

Centre 2010). In Alberta, Canada, Arctic 

grayling are native to the Athabasca, 

Peace, and Hay River drainages. In 

Alberta, the species has undergone a 

range contraction of about 40 percent, 

and half of the province’s 

subpopulations have declined in 

abundance by more than 90 percent 

(Alberta Sustainable Resource 

Development (ASRD) 2005, p. iv). 

Distribution in the Conterminous 

United States 

Two disjunct groups of Arctic 

grayling were native to the 

conterminous United States: One in the 

upper Missouri River basin in Montana 

and Wyoming (extant in Montana, see 

Figure 2), and another in Michigan that 

was extirpated in the late 1930s (Hubbs 

and Lagler 1949, p. 44). Michigan 

grayling formerly occurred in the Otter 

River of the Lake Superior drainage in 

northern Michigan and in streams of the 

lower peninsula of Michigan in both the 

Lake Michigan and Lake Huron 

drainages including the Au Sable, 

Cheboygan, Jordan, Pigeon, and Rifle 

Rivers (Vincent 1962, p. 12). 

Introduced Lake Dwelling Arctic 

Grayling in the Upper Missouri River 


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System and western U.S. populations of 

Arctic grayling have been established in 

lakes outside their native range in 

Arizona, Colorado, Idaho, Montana, 

New Mexico, Utah, Washington, and 

Wyoming (Vincent 1962, p. 15; Montana 

Fisheries Information System (MFISH) 

2009; NatureServe 2010). Stocking of 

hatchery grayling in Montana has been 

particularly extensive, and there are 

thought to be up to 78 introduced 

lacustrine (lake-dwelling) populations 

resulting from these introductions (see 

Table 1 below). Over three-quarters of 

these introductions (79.5 percent) were 

established outside the native 

geographic range of upper Missouri 

River grayling, while only 16 (20.5 

percent) were established within the 

watershed boundary of the upper 

Missouri River system. 

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FIGURE 2. Historical (dark grey lines) 

and current distribution (stars and 

circled portion of Big Hole River) of 

native Arctic grayling in the upper 

Missouri River basin. White bars denote 

mainstem river dams that are total 

barriers to upstream passage by fish. 

TABLE 1. INTRODUCED LAKE-DWELLING POPULATIONS OF ARCTIC GRAYLING IN MONTANA. THE PRIMARY DATA SOURCE

FOR THESE DESIGNATIONS IS MFISH (2009). 

River Basin Number of Introduced 

(Exotic) Populationsa

Outside Native Geographic Range In Montana 

Columbia River 23 

Middle Missouri River 2 

Saskatchewan River 1 

Yellowstone River 36b

Within Watershed Boundary Of Native Geographic Range In Montana 

Upper Missouri River 16 

Total Exotic Populations 78 

aList of populations does not include lake populations derived from attempts to re-establish fluvial populations in Montana, native adfluvial populations, or genetic reserves of Big Hole River grayling. bMany of these populations may not reproduce naturally and are only sustained through repeated stocking (Montana Fish, Wildlife and Parks 

2009, entire). 

For the purposes of this finding, we 

are analyzing a petitioned entity that 

includes, at its maximum extent, 

populations of Arctic grayling 

considered native to the upper Missouri 

River. Introduced populations present 

in Montana (e.g., Table 1) or elsewhere 

are not considered as part of the listable 

entity because we do not consider them 

to be native populations. Neither the 

Act nor our implementing regulations 

expressly address whether introduced 

populations should be considered part 

of an entity being evaluated for listing, 

and no Service policy addresses the 

issue. Consequently, in our evaluation 

of whether or not to include introduced 

populations in the potential listable 

entity we considered the following: (1) 

Our interpretation of the intent of the 

Act with respect to the disposition of 

native populations, (2) a policy used by 

the National Marine Fishery Service 

(NMFS) to evaluate whether hatcheryorigin populations warrant inclusion in 

the listable entity, and (3) a set of 

guidelines from another organization 

(International Union for Conservation of 

Nature and Natural Resources (IUCN)) 

with specific criteria for evaluating the 

conservation contribution of introduced 

populations. 

Intent of the Endangered Species Act 

The primary purpose of the Act is to 

provide a means whereby the 

ecosystems upon which endangered 

species and threatened species depend 

may be conserved. The Service has 

interpreted the Act to provide a 

statutory directive to conserve species 

in their native ecosystems (49 FR 33890, 

August 27, 1984) and to conserve 

genetic resources and biodiversity over 

a representative portion of a taxon’s 

historical occurrence (61 FR 4723, 

February 7, 1996). This priority on 

natural populations is evident in the 

Service’s DPS policy within the third 

significance criteria. In that, a discrete 

population segment may be significant 

if it represents the only surviving 

natural occurrence of the taxon that may 

be more abundant elsewhere as an 

introduced population outside of its 

historical range. 

National Marine Fishery Service 

Hatchery Policy 

In 2005, the NMFS published a final 

policy on the consideration of hatcheryorigin fish in Endangered Species Act 

listing determinations for Pacific salmon 

and steelhead (anadromous 

Oncorhynchus spp.) (NMFS 2005, 

entire). A central tenet of this policy is 

the primacy of the conservation of 

naturally spawning salmon populations 

and the ecosystems on which they 

depend, consistent with the intent of the 

Act (NMFS 2005, pp. 37211, 37214). 

The policy recognizes that properly 

managed hatchery programs may 

provide some conservation benefit to 

the evolutionary significant unit (ESU, 

which is analogous to a DPS but applied 

to Pacific salmon) (NMFS 2005, p. 

37211), and that hatchery stocks that 

contribute to survival and recovery of an 

ESU are considered during a listing 

decision (NMFS 2005, p. 37209). The 

policy states that since hatchery stocks 

are established and maintained with the 

intent of furthering the viability of wild 

populations in the ESU, that those 

hatchery populations have an explicit 

conservation value. Genetic divergence 

is the preferred metric to determine if 

hatchery fish should be included in the 

ESU, but NMFS recognizes that these 

data may be lacking in most cases 

(NMFS 2005, p. 37209). Thus, proxies 

for genetic divergence can be used, such 

as the length of time a stock has been 

isolated from its source population, the 

degree to which natural broodstock has 

been regularly incorporated into the 

hatchery population, the history of nonESU fish or eggs in the hatchery 

population, and the attention given to 

genetic considerations in selecting and 

mating broodstocks (NMFS 2005, p. 

37209). 

The NMFS policy applies to 

artificially propagated (hatchery) 

populations. In this finding, however, 

the Service is deciding whether selfsustaining populations introduced 

outside its natural range should be 

included in the listable entity. Thus, the 

NMFS policy is not directly applicable. 

Nonetheless, if the NFMS policy’s 

criteria are applied to the introduced 

lake-dwelling populations of Arctic 

grayling in Montana and elsewhere, 

these populations do not appear to 

warrant inclusion in the entity being 

evaluated for listing. First, there does 

not appear to be any formally 

recognized conservation value for the 


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introduced populations of Arctic 

grayling, and they are not being used in 

restoration programs. Recent genetic 

analysis indicates that many of the 

introduced Arctic grayling populations 

in Montana are derived, in part, from 

stocks in the Red Rock Lakes system 

(Peterson and Ardren 2009, p. 1767). 

Nonetheless, there have been concerns 

that introduced, lake-dwelling 

populations could pose genetic risks to 

the native fluvial population (Arctic 

Grayling Workgroup (AGW) 1995, p. 

15), and in practice, these introduced 

populations have not been used for any 

conservation purpose. In fact, efforts are 

currently underway to establish a 

genetically pure brood reserve 

population of Red Rock Lakes grayling 

to be used for conservation purposes 

(Jordan 2010, pers. comm.), analogous to 

the brood reserves maintained for Arctic 

grayling from the Big Hole River (Rens 

and Magee 2007, pp. 22–24). 

Second, introduced populations in 

lakes have apparently been isolated 

from their original source stock for 

decades without any supplementation 

from the wild. These populations were 

apparently established without any 

formal genetic consideration to selecting 

and mating broodstock, the source 

populations were not well documented 

(Peterson and Ardren 2009, p. 1767), 

and the primary intent of culturing and 

introducing these grayling appears to 

have been to provide recreational 

fishing opportunities in high mountain 

lakes. 

Guidelines Used in Other Evaluation 

Systems 

The IUCN uses its Red List system to 

evaluate the conservation status and 

relative risk of extinction for species, 

and to catalogue and highlight plant and 

animal species that are facing a higher 

risk of global extinction (http:// 

www.iucnredlist.org). IUCN does not use 

the term ‘‘listable entity’’ as the Service 

does; however, IUCN does clarify that 

their conservation ranking criteria apply 

to any taxonomic group at the species 

level or below (IUCN 2001, p.4). 

Further, the IUCN guidelines for species 

status and scope of the categorization 

process focus on wild populations 

inside their natural range (IUCN 2001, 

p. 4; 2003, p. 10) or so-called ‘‘benign’’ 

or ‘‘conservation introductions,’’ which 

are defined as attempts to establish a 

species, for the purpose of conservation, 

outside its recorded distribution, when 

suitable habitat is lacking within the 

historical range (IUCN 1998, p. 6; 2003, 

pp. 6, 10). Guidelines for evaluating 

conservation status under the IUCN 

exclude introduced populations located 

outside the recorded distribution of the 

species if such populations were 

established for commercial or sporting 

purposes (IUCN 1998, p. 5; 2003, p. 24). 

In effect, the IUCN delineates between 

introduced and native populations in 

that non-benign introductions do not 

qualify for evaluation under the IUCN 

Red List system. Naturalized 

populations of Arctic grayling in lakes 

thus do not meet the IUCN criterion for 

a wild population that should be 

considered when evaluating the species 

status for two reasons. First, there 

remains ‘suitable habitat’ for Arctic 

grayling in its native range, as 

evidenced by extant native populations 

in the Big Hole River, Madison River, 

Miner Lake, Mussigbrod Lake, and Red 

Rock Lakes. Second, the naturalized 

populations derived from widespread 

stocking were apparently aimed at 

establishing recreational fisheries. 

Our interpretation is that the ESA is 

intended to preserve native populations 

in their ecosystems. While hatchery or 

introduced populations of fishes may 

have some conservation value, this does 

not appear to be the case with 

introduced populations of Arctic 

grayling in the conterminous United 

States. These populations were 

apparently established to support 

recreational fisheries, and without any 

formal genetic consideration to selecting 

and mating broodstock, and are not part 

of any conservation program to benefit 

the native populations. Consequently, 

we do not consider the introduced 

populations of Arctic grayling in 

Montana and elsewhere in the 

conterminous United States, including 

those in lakes and in an irrigation canal 

(Sun River Slope Canal), to be part of 

the listable entity. 

Native Distribution in the Upper 

Missouri River System 

The first Euro-American ‘‘discovery’’ 

of Arctic grayling in North America is 

attributed to members of the Lewis and 

Clark Expedition, who encountered the 

species in the Beaverhead River in 

August 1805 (Nell and Taylor 1996, p. 

133). Vincent (1962, p. 11) and Kaya 

(1992, pp. 47–51) synthesized accounts 

of Arctic grayling occurrence and 

abundance from historical surveys and 

contemporary monitoring to determine 

the historical distribution of the species 

in the upper Missouri River system 

(Figure 2). We base our conclusions on 

the historical distribution of Arctic 

grayling in the upper Missouri River 

basin on these two reviews. Arctic 

grayling were widely but irregularly 

distributed in the upper Missouri River 

system above the Great Falls in Montana 

and in northwest Wyoming within the 

present-day location of Yellowstone 

National Park (Vincent 1962, p. 11). 

They were estimated to inhabit up to 

2,000 kilometers (km) (1,250 miles (mi)) 

of stream habitat until the early 20th 

century (Kaya 1992, pp. 47–51). Arctic 

grayling were reported in the mainstem 

Missouri River, as well as in the Smith, 

Sun, Jefferson, Madison, Gallatin, Big 

Hole, Beaverhead, and Red Rock Rivers 

(Vincent 1962, p. 11; Kaya 1992, pp. 47– 

51; USFWS 2007; 72 FR 20307, April 

24, 2007). ‘‘Old-timer’’ accounts report 

that the species may have been present 

in the Ruby River, at least seasonally 

(Magee 2005, pers. comm.), and were 

observed as recently as the early 1970s 

(Holton, undated). 

Fluvial Arctic grayling were 

historically widely distributed in the 

upper Missouri River basin, but a few 

adfluvial populations also were native 

to the basin. For example, Arctic 

grayling are native to Red Rock Lakes, 

in the headwaters of the Beaverhead 

River (Vincent 1962, pp. 112–121; Kaya 

1992, p. 47). Vincent (1962, p. 120) 

stated that Red Rock Lakes were the 

only natural lakes in the upper Missouri 

River basin accessible to colonization by 

Arctic grayling, and concluded that 

grayling there were the only native 

adfluvial population in the basin. 

However, it appears that Arctic grayling 

also were native to Elk Lake (in the Red 

Rocks drainage; Kaya 1990, p. 44) and 

a few small lakes in the upper Big Hole 

River drainage (Peterson and Ardren 

2009, p. 1768). 

The distribution of native Arctic 

grayling in the upper Missouri River 

went through a dramatic reduction in 

the first 50 years of the 20th century, 

especially in riverine habitats (Vincent 

1962, pp. 86–90, 97–122, 127–129; Kaya 

1992, pp. 47–53). The native 

populations that formerly resided in the 

Smith, Sun, Jefferson, Beaverhead, 

Gallatin, and mainstem Missouri Rivers 

are considered extirpated, and the only 

remaining indigenous fluvial population 

is found in the Big Hole River and some 

if its tributaries (Kaya 1992, pp. 51–53). 

The fluvial form currently occupies only 

4 to 5 percent of its historic range in the 

Missouri River system (Kaya 1992, p. 

51). Other remaining native populations 

in the upper Missouri River occur in 

two small, headwater lakes in the upper 

Big Hole River system (Miner and 

Mussigbrod Lakes); the Madison River 

upstream from Ennis Reservoir; and the 

Red Rock Lakes in the headwaters of the 

Beaverhead River system (Everett 1986, 

p. 7; Kaya 1992, p. 53; Peterson and 

Ardren 2009, pp. 1762, 1768; Figure 1 

above, and Table 2 below). 


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TABLE 2. EXTANT NATIVE ARCTIC GRAYLING POPULATIONS IN THE UPPER MISSOURI RIVER BASIN. 

Big Hole River Drainagea

1. Big Hole River 

2. Miner Lake 

3. Mussigbrod Lake 

Madison River Drainage 

4. Madison River-Ennis Reservoir 

Beaverhead River Drainage 

5. Red Rock Lakes 

aArctic grayling also occur in Pintler Lake in the Big Hole River drainage, but this population has not been evaluated with genetic markers to 

determine whether it constitutes a native remnant population. 

Origins, Biogeography, and Genetics of 

Arctic Grayling in North America 

North American Arctic grayling are 

most likely descended from Eurasian 

Thymallus that crossed the Bering land 

bridge during or before the Pleistocene 

glacial period (Stamford and Taylor 

2004, pp. 1533, 1546). A Eurasian origin 

is suggested by the substantial 

taxonomic diversity found in the genus 

in that region. There were multiple 

opportunities for freshwater faunal 

exchange between North America and 

Asia during the Pleistocene, but genetic 

divergence between North American 

and Eurasian Arctic grayling suggests 

that the species could have colonized 

North America as early as the mid-late 

Pliocene (more than 3 million years ago) 

(Stamford and Taylor 2004, p. 1546). 

The North American distribution of 

Arctic grayling was strongly influenced 

by patterns of glaciation. Genetic studies 

of grayling using mitochondrial DNA 

(mtDNA, maternally-inherited DNA 

located in cellular organelles called 

mitochondria) and microsatellite DNA 

(repeating sequences of nuclear DNA) 

have shown that North American Arctic 

grayling consist of at least three major 

lineages that originated in distinct 

Pleistocene glacial refugia (Stamford 

and Taylor 2004, p. 1533). These three 

groups include a South Beringia lineage 

found in western Alaska to northern 

British Columbia, Canada; a North 

Beringia lineage found on the North 

Slope of Alaska, the lower Mackenzie 

River, and to eastern Saskatchewan; and 

a Nahanni lineage found in the lower 

Liard River and the upper Mackenzie 

River drainage (Stamford and Taylor 

2004, pp. 1533, 1540). The Nahanni 

lineage is the most genetically distinct 

group (Stamford and Taylor 2004, pp. 

1541–1543). Arctic grayling from the 

upper Missouri River basin were 

tentatively placed in the North Beringia 

lineage because a small sample (three 

individuals) of Montana grayling shared 

a mtDNA haplotype (form of the 

mtDNA) with populations in 

Saskatchewan and the lower Peace 

River, British Columbia (Stamford and 

Taylor 2004, p. 1538). 

The existing mtDNA data suggest that 

Missouri River Arctic grayling share a 

common ancestry with the North 

Beringia lineage, but other genetic 

markers and biogeographic history 

indicate that Missouri River grayling 

have been physically and 

reproductively isolated from northern 

populations for millennia. The most 

recent ancestors of Missouri River 

Arctic grayling likely spent the last 

glacial cycle in an ice-free refuge south 

of the Laurentide and Cordilleran ice 

sheets. Pre-glacial colonization of the 

Missouri River basin by Arctic grayling 

was possible because the river flowed to 

the north and drained into the ArcticHudson Bay prior to the last glacial 

cycle (Cross et al. 1986, pp. 374–375; 

Pielou 1991, pp. 194–195). Low mtDNA 

diversity observed in a small number of 

Montana grayling samples and a shared 

ancestry with Arctic grayling from the 

north Beringia lineage suggest a more 

recent, post-glacial colonization of the 

upper Missouri River basin. In contrast, 

microsatellite DNA show substantial 

divergence between Montana and 

Saskatchewan (i.e., same putative 

mtDNA lineage) (Peterson and Ardren 

2009, entire). Differences in the 

frequency and size distribution of 

microsatellite alleles between Montana 

populations and two Saskatchewan 

populations indicate that Montana 

grayling have been isolated long enough 

for mutations (i.e., evolution) to be 

responsible for the observed genetic 

differences. 

Additional comparison of 21 Arctic 

grayling populations from Alaska, 

Canada, and the Missouri River basin 

using 9 of the same microsatellite loci 

as Peterson and Ardren (2009, entire) 

further supports the distinction of 

Missouri River Arctic grayling relative 

to populations elsewhere in North 

America (USFWS, unpublished data). 

Analyses of these data using two 

different methods clearly separates 

sample fish from 21 populations into 

two clusters: one cluster representing 

populations from the upper Missouri 

River basin, and another cluster 

representing populations from Canada 

and Alaska (USFWS, unpublished data). 

These new data, although not yet peer 

reviewed, support the interpretation 

that the previous analyses of Stamford 

and Taylor (2004, entire) 

underestimated the distinctiveness of 

Missouri River Arctic grayling relative 

to other sample populations, likely 

because of the combined effect of small 

sample sizes and the lack of variation 

observed in the Missouri River for the 

markers used in that study (Stamford 

and Taylor 2004, pp. 1537–1538). Thus, 

these recent microsatellite DNA data 

suggest that Arctic grayling may have 

colonized the Missouri River before the 

onset of Wisconsin glaciation (more 

than 80,000 years ago). 

Genetic relationships among native 

and introduced populations of Arctic 

grayling in Montana have recently been 

investigated (Peterson and Ardren 2009, 

entire). Introduced, lake-dwelling 

populations of Arctic grayling trace 

much of their original ancestry to Red 

Rock Lakes (Peterson and Ardren 2009, 

p. 1767), and stocking of hatchery 

grayling did not appear to have a large 

effect on the genetic composition of the 

extant native populations (Peterson and 

Ardren 2009, p. 1768). Differences 

between native populations of the two 

grayling ecotypes (adfluvial, fluvial) do 

not appear to be as large as differences 

resulting from geography (i.e., drainage 

of origin). 


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Habitat 

Arctic grayling generally require clear, 

cold water. Selong et al. (2001, p. 1032) 

characterized Arctic grayling as 

belonging to a ‘‘coldwater’’ group of 

salmonids, which also includes bull 

trout (Salvelinus confluentus) and 

Arctic char (Salvelinus alpinus). Hubert 

et al. (1985, p. 24) developed a habitat 

suitability index study for Arctic 

grayling and concluded that thermal 

habitat was optimal between 7 to 17 °C 

(45 to 63 °F), but became unsuitable 

above 20°C (68°F). Arctic grayling fry 

may be more tolerant of high water 

temperature than adults (LaPerriere and 

Carlson 1973, p. 30; Feldmeth and 

Eriksen 1978, p. 2041). 

Having a broad, nearly-circumpolar 

distribution, Arctic grayling occupy a 

variety of habitats including small 

streams, large rivers, lakes, and even 

bogs (Northcote 1995, pp. 152–153; 

Scott and Crossman 1998, p. 303). They 

may even enter brackish water (less than 

or equal to 4 parts per thousand) when 

migrating between adjacent river 

systems (West et al. 1992, pp. 713–714). 

Native populations are found at 

elevations ranging from near sea level, 

such as in Bristol Bay, Alaska, to highelevation montane valleys (more than 

1,830 meters (m) or 6,000 feet (ft)), such 

as the Big Hole River and Centennial 

Valley in southwestern Montana. 

Despite this broad distribution, Arctic 

grayling have specific habitat 

requirements that can constrain their 

local distributions, especially water 

temperature and channel gradient. At 

the local scale, Arctic grayling prefer 

cold water and are often associated with 

spring-fed habitats in regions with 

warmer climates (Vincent 1962, p. 33). 

Arctic grayling are generally not found 

in swift, high-gradient streams, and 

Vincent (1962, p. 36–37, 41–43) 

characterized typical Arctic grayling 

habitat in Montana (and Michigan) as 

low-to-moderate gradient (less than 4 

percent) streams and rivers with low-tomoderate water velocities (less than 60 

centimeters/sec). Juvenile and adult 

Arctic grayling in streams and rivers 

spend much of their time in pool habitat 

(Kaya 1990 and references therein, p. 

20; Lamothe and Magee 2003, pp. 13– 

14). 

Breeding 

Arctic grayling typically spawn in the 

spring or early summer, depending on 

latitude and elevation (Northcote 1995, 

p. 149). In Montana, Arctic grayling 

generally spawn from late April to midMay by depositing adhesive eggs over 

gravel substrate without excavating a 

nest (Kaya 1990, p. 13; Northcote 1995, 

p. 151). In general, the reproductive 

ecology of Arctic grayling differs from 

other salmonid species (trout and 

salmon) in that Arctic grayling eggs tend 

to be comparatively small; thus, they 

have higher relative fecundity (females 

have more eggs per unit body size). 

Males establish and defend spawning 

territories rather than defending access 

to females (Northcote 1995, pp. 146, 

150–151). The time required for 

development of eggs from embryo until 

they emerge from stream gravel and 

become swim-up fry depends on water 

temperature (Northcote 1995, p. 151). In 

the upper Missouri River basin, 

development from embryo to fry 

averages about 3 weeks (Kaya 1990, pp. 

16–17). Small, weakly swimming fry 

(typically 1–1.5 centimeters (cm) (0.4– 

0.6 in.) at emergence) prefer lowvelocity stream habitats (Armstrong 

1986, p. 6; Kaya 1990, pp. 23–24; 

Northcote 1995, p. 151). 

Arctic grayling of all ages feed 

primarily on aquatic and terrestrial 

invertebrates captured on or near the 

water surface, but also will feed 

opportunistically on fish and fish eggs 

(Northcote 1995, pp. 153–154; Behnke 

2002, p. 328). Feeding locations for 

individual fish are typically established 

and maintained through size-mediated 

dominance hierarchies where larger 

individuals defend favorable feeding 

positions (Hughes 1992, p. 1996). 

Life History Diversity 

Migratory behavior is a common lifehistory trait in salmonid fishes such as 

Arctic grayling (Armstrong 1986, pp. 7– 

8; Northcote 1995, pp. 156–158; 1997, 

pp. 1029, 1031–1032, 1034). In general, 

migratory behavior in Arctic grayling 

and other salmonids results in cyclic 

patterns of movement between refuge, 

rearing-feeding, and spawning habitats 

(Northcote 1997, p. 1029). 

Arctic grayling may move to refuge 

habitat as part of a regular seasonal 

migration (e.g., in winter), or in 

response to episodic environmental 

stressors (e.g., high summer water 

temperatures). In Alaska, Arctic grayling 

in rivers typically migrate downstream 

in the fall, moving into larger streams or 

mainstem rivers that do not completely 

freeze (Armstrong 1986, p. 7). In Arctic 

rivers, fish often seek overwintering 

habitat influenced by groundwater 

(Armstrong 1986, p. 7). In some 

drainages, individual fish may migrate 

considerable distances (greater than 150 

km or 90 mi) to overwintering habitats 

(Armstrong 1986, p. 7). In the Big Hole 

River, Montana, similar downstream 

and long-distance movement to 

overwintering habitat has been observed 

in Arctic grayling (Shepard and Oswald 

1989, pp. 18–21, 27). In addition, Arctic 

grayling in the Big Hole River may move 

downstream in proximity to colder 

tributary streams in summer when 

thermal conditions in the mainstem 

river become stressful (Lamothe and 

Magee 2003, p. 17). 

In spring, mature Arctic grayling leave 

overwintering areas and migrate to 

suitable spawning sites. In river 

systems, this typically involves an 

upstream migration to tributary streams 

or shallow riffles within the mainstem 

(Armstrong 1986, p. 8). Arctic grayling 

in lakes typically migrate to either the 

inlet or outlet to spawn (Armstrong 

1986, p. 8; Northcote 1997, p. 148). In 

either situation, Arctic grayling 

typically exhibit natal homing, whereby 

individuals spawn in or near the 

location where they were born 

(Northcote 1997, pp. 157–160). 

Fry from river populations typically 

seek feeding and rearing habitats in the 

vicinity where they were spawned 

(Armstrong 1986, pp. 6–7; Northcote 

1995, p. 156), while those from lake 

populations migrate downstream (inlet 

spawners) or upstream (outlet spawners) 

to the adjacent lake. Following 

spawning, adults move to appropriate 

feeding areas if they are not adjacent to 

spawning habitat (Armstrong 1986, pp. 

7–8). Juvenile Arctic grayling may 

undertake seasonal migrations between 

feeding and overwintering habitats until 

they reach maturity and add the 

spawning migration to this cycle 

(Northcote 1995, pp. 156–157). 

Life History Diversity in Arctic Grayling 

in the Upper Missouri River 

Two general life-history forms or 

ecotypes of native Arctic grayling occur 

in the upper Missouri River Arctic: 

Fluvial and adfluvial. Fluvial fish use 

river or stream (lotic) habitat for all of 

their life cycles and may undergo 

extensive migrations within river 

habitat. Adfluvial fish live in lakes and 

migrate to tributary streams to spawn. 

These same life-history forms also are 

expressed by Arctic grayling elsewhere 

in North America (Northcote 1997, p. 

1030). Historically, the fluvial lifehistory form predominated in the 

Missouri River basin above the Great 

Falls, perhaps because there were only 

a few lakes accessible to natural 

colonization of Arctic grayling that 

would permit expression of the 

adfluvial ecotype (Kaya 1992, p. 47). 

The fluvial and adfluvial life-history 

forms of Arctic grayling in the upper 

Missouri River do not appear to 

represent distinct evolutionary lineages. 

Instead, they appear to represent an 

example of adaptive radiation (Schluter 

2000, p. 1), whereby the forms 


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differentiated from a common ancestor 

developed traits that allowed them to 

exploit different habitats. The primary 

evidence for this conclusion is genetic 

data that indicate that within the 

Missouri River basin the two ecotypes 

are more closely related to each other 

than they are to the same ecotype 

elsewhere in North America (Redenbach 

and Taylor 1999, pp. 27–28; Stamford 

and Taylor 2004, p. 1538; Peterson and 

Ardren 2009, p. 1766). Historically, 

there may have been some genetic 

exchange between the two life-history 

forms as individuals strayed or 

dispersed into different populations 

(Peterson and Ardren 2009, p. 1770), but 

the genetic structure of current 

populations in the upper Missouri River 

basin is consistent with reproductive 

isolation. 

The fluvial and adfluvial forms of 

Arctic grayling appear to differ in their 

genetic characteristics, but there appears 

to be some plasticity in behavior where 

individuals from a population can 

exhibit a range of behaviors. Arctic 

grayling fry in Montana can exhibit 

heritable, genetically-based differences 

in swimming behavior between fluvial 

and adfluvial ecotypes (Kaya 1991, pp. 

53, 56–58; Kaya and Jeanes 1995, pp. 

454, 456). Progeny of Arctic grayling 

from the fluvial ecotype exhibited a 

greater tendency to hold their position 

in flowing water relative to progeny 

from adfluvial ecotypes (Kaya 1991, pp. 

53, 56–58; Kaya and Jeanes 1995, pp. 

454, 456). Similarly, young grayling 

from inlet and outlet spawning adfluvial 

ecotypes exhibited an innate tendency 

to move downstream and upstream, 

respectively (Kaya 1989, pp. 478–480). 

All three studies (Kaya 1989, entire; 

1991, entire; Kaya and Jeanes 1995, 

entire) demonstrate that the response of 

fry to flowing water depended strongly 

on the life-history form (ecotype) of the 

source population, and that this 

behavior has a genetic basis. However, 

behavioral responses also were 

mediated by environmental conditions 

(light—Kaya 1991, pp. 56–57; light and 

water temperature—Kaya 1989, pp. 

477–479), and some progeny of each 

ecotype exhibited behavior 

characteristic of the other; for example 

some individuals from the fluvial 

ecotype moved downstream rather than 

holding position, and some individuals 

from an inlet-spawning adfluvial 

ecotype held position or moved 

upstream (Kaya 1991, p. 58). These 

observations indicate that some 

plasticity for behavior exists, at least for 

very young Arctic grayling. 

However, the ability of one ecotype of 

Arctic grayling to give rise to a 

functional population of the other 

ecotype within a few decades is much 

less certain, and may parallel the 

differences in plasticity that have 

evolved between river- and lake-type 

European grayling (Salonen 2005, 

entire). Circumstantial support for 

reduced plasticity in adfluvial Arctic 

grayling comes from observations that 

adfluvial fish stocked in river habitats 

almost never establish populations 

(Kaya 1990, pp. 31–34). In contrast, a 

population of Arctic grayling in the 

Madison River that would have 

presumably expressed a fluvial ecotype 

under historical conditions has 

apparently adapted to an adfluvial lifehistory after construction of an 

impassible dam, which impounded 

Ennis Reservoir (Kaya 1992, p. 53; 

Jeanes 1996, pp. 54). We note that 

adfluvial Arctic grayling retain some 

life-history flexibility—at least in lake 

environments—as naturalized 

populations derived from inletspawning stocks have established 

outlet-spawning demes (a deme is a 

local populations that shares a distinct 

gene pool) in Montana and in 

Yellowstone National Park (Kruse 1959, 

p. 318; Kaya 1989, p. 480). While in 

some cases Arctic grayling may be able 

to adapt or adjust rapidly to a new 

environment, the frequent failure of 

introductions of Arctic grayling suggest 

a cautionary approach to the loss of 

particular life-history forms is 

warranted. Healey and Prince (1995, 

entire) reviewed patterns of genotypic 

and phenotypic variation in Pacific 

salmon and warn that recovery of lost 

life-history forms may not follow 

directly from conservation of the 

genotype (p. 181), and reason that the 

critical conservation unit is the 

population within its habitat (p. 181). 

Age and Growth 

Age at maturity and longevity in 

Arctic grayling varies regionally and is 

probably related to growth rate, with 

populations in colder, northern 

latitudes maturing at later ages and 

having a greater lifespan (Kruse 1959, 

pp. 340–341; Northcote 1995 and 

references therein, pp. 155–157). Arctic 

grayling in the upper Missouri River 

typically mature at age 2 (males) or age 

3 (females), and individuals greater than 

age 6 are rare (Kaya 1990, p. 18; Magee 

and Lamothe 2003, pp. 16–17). 

Similarly, Nelson (1954, pp. 333–334) 

observed that the majority of the Arctic 

grayling spawning in two tributaries in 

the Red Rock Lakes system, Montana, 

were age 3, and the oldest individuals 

aged from a larger sample were age 6. 

Mogen (1996, pp. 32–34) found that 

Arctic grayling spawning in Red Rock 

Creek were mostly ages 2 to 5, but he 

did encounter some individuals age 7. 

Generally, growth rates of Arctic 

grayling are greatest during the first 

years of life then slow dramatically after 

maturity. Within that general pattern, 

there is substantial variation among 

populations from different regions. 

Arctic grayling populations in Montana 

(Big Hole River and Red Rock Lakes) 

appear to have very high growth rates 

relative to those from British Columbia, 

Asia, and the interior and North Slope 

of Alaska (Carl et al. 1992, p. 240; 

Northcote 1995, pp. 155–157; Neyme 

2005, p. 28). Growth rates of Arctic 

grayling from different management 

areas in Alberta are nearly as high as 

those observed in Montana grayling 

(ASRD 2005, p. 4). 

Distinct Population Segment 

In its stipulated settlement with 

Plaintiffs, the Service agreed to consider 

the appropriateness of DPS designations 

for Arctic grayling populations in the 

upper Missouri River basin that 

included: (a) All life ecotypes or 

histories, (b) the fluvial ecotype, and (c) 

the adfluvial ecotype. The fluvial 

ecotype has been the primary focus of 

past Service action and litigation, but 

the Service also has alluded to the 

possibility of alternative DPS 

designations in previous candidate 

species assessments (USFWS 2005, p. 

11). Since the 2007 finding (72 FR 

20305), additional research has been 

conducted and new information on the 

genetics of Arctic grayling is available. 

This finding contains a more 

comprehensive and robust distinct 

population segment analysis than the 

2007 finding. 

Distinct Population Segment Analysis 

for Native Arctic Graying in the Upper 

Missouri River 

Discreteness 

The discreteness standard under the 

Service’s and National Oceanic and 

Atmospheric Administration’s (NOAA) 

joint Policy Regarding the Recognition 

of Distinct Vertebrate Population 

Segments Under the Endangered 

Species Act (61 FR 4722) requires an 

entity to be adequately defined and 

described in some way that 

distinguishes it from other 

representatives of its species. A segment 

is discrete if it is: (1) Markedly 

separated from other populations of the 

same taxon as consequence of physical, 

physiological, ecological, or behavioral 

factors (quantitative measures of genetic 

or morphological discontinuity may 

provide evidence of this separation); or 

(2) delimited by international 


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governmental boundaries within which 

differences in control of exploitation, 

management of habitat, conservation 

status, or regulatory mechanisms exist 

that are significant in light of section 

4(a)(1)(D) of the ESA. 

Arctic grayling native to the upper 

Missouri River are isolated from 

populations of the species inhabiting 

the Arctic Ocean, Hudson Bay, and 

north Pacific Ocean drainages in Asia 

and North America (see Figure 1). Arctic 

grayling native to the upper Missouri 

River occur as a disjunct group of 

populations approximately 800 km (500 

mi) to the south of the next-nearest 

Arctic grayling population in central 

Alberta, Canada. Missouri River Arctic 

grayling have been isolated from other 

populations for at least 10,000 years 

based on historical reconstruction of 

river flows at or near the end of the 

Pleistocene (Cross et al. 1986, p. 375; 

Pileou 1991, pp. 10–11;). Genetic data 

confirm Arctic grayling in the Missouri 

River basin have been reproductively 

isolated from populations to the north 

for millennia (Everett 1986, pp. 79–80; 

Redenbach and Taylor 1999, p. 23; 

Stamford and Taylor 2004, p. 1538; 

Peterson and Ardren 2009, pp. 1764– 

1766; USFWS, unpublished data). 

Consequently, we conclude that Arctic 

grayling native to the upper Missouri 

River are markedly separated from other 

native populations of the taxon as a 

result of physical factors (isolation), and 

therefore meet the first criterion of 

discreteness under the DPS policy. As a 

result, Arctic grayling native to the 

upper Missouri River are considered a 

discrete population according to the 

DPS policy. Because the entity meets 

the first criterion (markedly separated), 

an evaluation with respect to the second 

criterion (international boundaries) is 

not needed. 

Significance 

If we determine that a population 

meets the DPS discreteness element, we 

then consider whether it also meets the 

DPS significance element. The DPS 

policy states that, if a population 

segment is considered discrete under 

one or more of the discreteness criteria, 

its biological and ecological significance 

will be considered in light of 

congressional guidance that the 

authority to list DPSs be used 

‘‘sparingly’’ while encouraging the 

conservation of genetic diversity (see 

U.S. Congress 1979, Senate Report 151, 

96th Congress, 1st Session). In making 

this determination, we consider 

available scientific evidence of the 

discrete population’s importance to the 

taxon to which it belongs. Since precise 

circumstances are likely to vary 

considerably from case to case, the DPS 

policy does not describe all the classes 

of information that might be used in 

determining the biological and 

ecological importance of a discrete 

population. However, the DPS policy 

does provide four possible reasons why 

a discrete population may be significant. 

As specified in the DPS policy, this 

consideration of significance may 

include, but is not limited to, the 

following: (1) Persistence of the discrete 

population segment in a unique or 

unusual ecological setting; (2) evidence 

that loss of the discrete segment would 

result in a significant gap in the range 

of the taxon; (3) evidence that the 

discrete population segment represents 

the only surviving natural occurrence of 

the taxon that may be more abundant 

elsewhere as an introduced population 

outside of its historic range; or (4) 

evidence that the discrete population 

segment differs markedly from other 

populations of the species in its genetic 

characteristics. 

Unique Ecological Setting 

Water temperature is a key factor 

influencing the ecology and physiology 

of ectothermic (body temperature 

regulated by ambient environmental 

conditions) salmonid fishes, and can 

dictate reproductive timing, growth and 

development, and life-history strategies. 

Groundwater temperatures can be 

related to air temperatures (Meisner 

1990, p. 282), and thus reflect the 

regional climatic conditions. Warmer 

groundwater influences ecological 

factors such as food availability, the 

efficiency with which food is converted 

into energy for growth and 

reproduction, and ultimately growth 

rates of aquatic organisms (Allan 1995, 

pp. 73–79). Aquifer structure and 

groundwater temperature is important 

to salmonid fishes because groundwater 

can strongly influence stream 

temperature, and consequently egg 

incubation and fry growth rates, which 

are strongly temperature-dependent 

(Coutant 1999, pp. 32–52; Quinn 2005, 

pp. 143–150). 

Missouri River Arctic grayling occur 

within the 4 to 7 °C (39 to 45 °F) ground 

water isotherm (see Heath 1983, p. 71; 

an isotherm is a line connecting bands 

of similar temperatures on the earth’s 

surface), whereas most other North 

American grayling are found in 

isotherms less than 4 °C, and much of 

the species’ range is found in areas with 

discontinuous or continuous permafrost 

(Meisner et al. 1988, p. 5). Much of the 

historical range of Arctic grayling in the 

upper Missouri River is encompassed by 

mean annual air temperature isotherms 

of 5 to 10 °C (41 to 50 °F) (USGS 2009), 

with the colder areas being in the 

headwaters of the Madison River in 

Yellowstone National Park. In contrast, 

Arctic grayling in Canada, Alaska, and 

Asia are located in regions encompassed 

by air temperature isotherms 5 °C and 

colder (41 °F and colder), with much of 

the species distributed within the 0 to 

-10 °C isolines (32 to 14 °F). This 

difference is significant because Arctic 

grayling in the Missouri River basin 

have evolved in isolation for millennia 

in a generally warmer climate than other 

populations. The potential for thermal 

adaptations makes Missouri River Arctic 

grayling a significant biological resource 

for the species under expected climate 

change scenarios. 

TABLE 3. DIFFERENCES BETWEEN THE ECOLOGICAL SETTING OF THE UPPER MISSOURI RIVER AND ELSEWHERE IN THE

SPECIES’ RANGE OF ARCTIC GRAYLING. 

Ecological Setting Variable Missouri River Rest of Taxon 

Ocean watershed Gulf of Mexico–Atlantic Ocean Hudson Bay, Arctic Ocean, or 

north Pacific 

Bailey’s Ecoregion Dry Domain: Temperate Steppe Polar Domain: Tundra & Subarctic 

Humid Temperate: Marine, 

Prairie, Warm Continental 

Mountains 

Air temperature (isotherm) 5 to 10 °C 

(41 to 50 °F) 

-15 to 5 °C 

(5 to 41 °F) 


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TABLE 3. DIFFERENCES BETWEEN THE ECOLOGICAL SETTING OF THE UPPER MISSOURI RIVER AND ELSEWHERE IN THE

SPECIES’ RANGE OF ARCTIC GRAYLING.—Continued 

Ecological Setting Variable Missouri River Rest of Taxon 

Groundwater temperature (isotherm) 4 to 7°C 

(39 to 45 °F) 

Less than 4 °C 

(less than 39 °F) 

Native occurrence of large-bodied fish predators on salmonids None, in most of the rangea Bull trout, lake trout, northern 

pike, taimen 

aLake trout are native to two small lakes in the upper Missouri River basin (Twin Lakes and Elk Lake), where their distributions presumably 

overlapped with the native range of Arctic grayling, so they would not have interacted with most Arctic grayling populations in the basin that were 

found in rivers. 

Arctic grayling in the upper Missouri 

River basin occur in a temperate 

ecoregion distinct from all other Arctic 

grayling populations worldwide, which 

occur in Arctic or sub-Arctic ecoregions 

dominated by Arctic flora and fauna. An 

ecoregion is a continuous geographic 

area within which there are associations 

of interacting biotic and abiotic features 

(Bailey 2005, pp. S14, S23). These 

ecoregions delimit large areas within 

which local ecosystems recur more or 

less in a predictable fashion on similar 

sites (Bailey 2005, p. S14). Ecoregional 

classification is hierarchical, and based 

on the study of spatial coincidences, 

patterning, and relationships of climate, 

vegetation, soil, and landform (Bailey 

2005, p. S23). The largest ecoregion 

categories are domains, which represent 

subcontinental areas of similar climate 

(e.g., polar, humid temperate, dry, and 

humid tropical) (Bailey 1994; 2005, p. 

S17). Domains are divided into 

divisions that contain areas of similar 

vegetation and regional climates. Arctic 

grayling in the upper Missouri River 

basin are the only example of the 

species naturally occurring in a dry 

domain (temperate steppe division; see 

Table 3 above). The vast majority of the 

species’ range is found in the polar 

domain (all of Asia, most of North 

America), with small portions of the 

range occurring in the humid temperate 

domain (northern British Columbia and 

southeast Alaska). Occupancy of 

Missouri River Arctic grayling in a 

temperate ecoregion is significant for 

two primary reasons. First, an ecoregion 

represents a suite of factors (climate, 

vegetation, landform) influencing, or 

potentially influencing, the evolution of 

species within that ecoregion. Since 

Missouri River Arctic grayling have 

existed for thousands of years in an 

ecoregion quite different from the 

majority of the taxon, they have likely 

developed adaptations during these 

evolutionary timescales that distinguish 

them from the rest of the taxon, even if 

we have yet to conduct the proper 

studies to measure these adaptations. 

Second, the occurrence of Missouri 

River Arctic grayling in a unique 

ecoregion helps reduce the risk of 

species-level extinction, as the different 

regions may respond differently to 

environmental change. 

Arctic grayling in the upper Missouri 

River basin have existed for at least 

10,000 years in an ecological setting 

quite different from that experienced by 

Arctic grayling elsewhere in the species’ 

range. The most salient aspects of this 

different setting relate to temperature 

and climate, which can strongly and 

directly influence the biology of 

ectothermic species (like Arctic 

grayling). Arctic grayling in the upper 

Missouri River have experienced 

warmer temperatures than most other 

populations. Physiological and lifehistory adaptation to local temperature 

regimes are regularly documented in 

salmonid fishes (Taylor 1991, pp. 191– 

193), but experimental evidence for 

adaptations to temperature, such as 

unusually high temperature tolerance or 

lower tolerance to colder temperatures, 

is lacking for Missouri River Arctic 

grayling because the appropriate studies 

have not been conducted. Lohr et al. 

(1996, p. 934) studied the upper thermal 

tolerances of Arctic grayling from the 

Big Hole River, but their research design 

did not include other populations from 

different thermal regimes, so it was not 

possible to make between-population 

contrasts under a common set of 

conditions. Arctic grayling from the 

upper Missouri River demonstrate very 

high growth rates relative to other 

populations (Northcote 1995, p. 157). 

Experimental evidence obtained by 

growing fish from populations under 

similar conditions would be needed to 

measure the relative influence of 

genetics (local adaptation) versus 

environment. 

An apex fish predator that preys 

successfully on salmonids has been 

largely absent from most of the upper 

Missouri River basin over evolutionary 

time scales (tens of thousands of years). 

This suggests that Arctic grayling in the 

upper Missouri River basin have faced 

a different selective pressure than Arctic 

grayling in many other areas of the 

species’ range, at least with respect to 

predation by fishes. Predators can exert 

a strong selective pressure on 

populations. One noteworthy aspect of 

the aquatic biota experienced by Arctic 

grayling in the upper Missouri River is 

the apparent absence of a large-bodied 

fish that would be an effective predator 

on juvenile and adult salmonids. In 

contrast, one or more species of large 

predatory fishes like northern pike 

(Esox lucius), bull trout, taimen (Hucho 

taimen), and lake trout (Salvelinus 

namaycush) are broadly distributed 

across much of the range of Arctic 

grayling in Canada and Asia (Northern 

pike—Scott and Crossman 1998, pp. 

302, 358; taimen—VanderZanden et al. 

2007, pp. 2281–2282; Esteve et al. 2009, 

p. 185; bull trout—Behnke 2002, pp. 

296, 330; lake trout —Behnke 2002, pp. 

296, 330). The only exceptions to this 

general pattern are where Arctic 

grayling formerly coexisted with lake 

trout native to Twin Lakes and Elk Lake 

(Beaverhead County) (Vincent 1963, pp. 

188–189), but both of these Arctic 

grayling populations are thought to be 

extirpated (Oswald 2000, pp. 10, 16; 

Oswald 2006, pers. comm.). The burbot 

(Lota lota) is a freshwater fish belonging 

to the cod family and is native to the 

Missouri, Big Hole, Beaverhead, Ruby, 

and Madison Rivers in Montana (MFISH 

2010); thus its distribution significantly 

overlapped the historical and current 

ranges of Arctic grayling in the upper 

Missouri River system. Burbot are 

voracious predators, but tend to be 

benthic (bottom-oriented) and 

apparently prefer the deeper portions of 

larger rivers and lakes. A few studies 

have investigated the diet of burbot 

where they overlap with native Arctic 

grayling in Montana, but did not detect 

any predation on Arctic grayling (Streu 

1990, pp. 16–20; Katzman 1998, pp. 98– 

100). Burbot apparently do not consume 

salmonids in significant amounts, even 

when they are very abundant (Katzman 

1998 and references therein, p. 106). 

The response of Arctic grayling in the 

Missouri River basin to introduced, 


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nonnative trout suggests they were not 

generally pre-adapted to cope with the 

presence of a large-bodied salmonid 

predator. Missouri River Arctic grayling 

lack a co-evolutionary history with 

brown trout, and there are repeated 

observations that the two species tend 

not to coexist and that brown trout 

displace Arctic grayling (Kaya 1992, p. 

56; 2000, pp. 14–15). We caution that 

competition with and predation by 

brown trout has not been directly 

studied with Arctic grayling, but at least 

some circumstantial evidence indicates 

that Missouri River Arctic grayling may 

not coexist well with brown trout. 

We conclude that the occurrence of 

Arctic grayling in the upper Missouri 

River is biogeographically important to 

the species, that grayling there have 

occupied a distinctly different 

ecological setting relative to the rest of 

the species (see Table 3 above), and that 

they have been on a different 

evolutionary trajectory for at least 

10,000 years. Consequently, we believe 

that Arctic grayling in the upper 

Missouri River occupy a unique 

ecological setting. The role that this 

unique setting plays in influencing 

adaptations or determining unique traits 

is unclear, and therefore a 

determination of the significance of this 

ecological setting to the taxon is 

unknown. 

Gap in the Range 

Arctic grayling in the upper Missouri 

River basin occur in an ocean drainage 

basin that is distinct from all other 

Arctic grayling populations worldwide. 

All other Arctic grayling occur in 

drainages of Hudson Bay, the Arctic 

Ocean, or the north Pacific Ocean; the 

Missouri River is part of the Gulf of 

Mexico–Atlantic Ocean drainage. The 

significance of occupancy of this 

drainage basin is that the upper 

Missouri River basin represents an 

important part of the species’ range from 

a biogeographic perspective. The only 

other population of Arctic grayling to 

live in a non-Arctic environment was 

the Michigan–Great Lakes population 

that was extirpated in the 1930s. 

Arctic grayling in Montana (southern 

extent is approximately 44°36′23′′ N 

latitude) represent the southern-most 

extant population of the species’ 

distribution since the Pleistocene 

glaciation (Figure 1). The next-closest 

native Arctic grayling population 

outside the Missouri River basin is 

found in the Pembina River 

(approximately 52°55′6.77′′ N latitude) 

in central Alberta, Canada, west of 

Edmonton (Blackburn and Johnson 

2004, pp. ii, 17; ASRD 2005, p. 6). Loss 

of the native Arctic grayling of the 

upper Missouri River would shift the 

southern distribution of Arctic grayling 

by more than 8° latitude. Such a 

dramatic range constriction would 

constitute a significant geographic gap 

in the species’ range, and eliminate a 

genetically distinct group of Arctic 

grayling, which may limit the species’ 

ability to cope with future 

environmental change. 

Marginal populations, defined as 

those on the periphery of the species’ 

range, are believed to have high 

conservation significance (see reviews 

by Scudder 1989, entire; Lesica and 

Allendorf 1995, entire; Fraser 2000, 

entire). Peripheral populations may 

occur in suboptimal habitats and thus 

be subjected to very strong selective 

pressures (Fraser 2000, p. 50). 

Consequently, individuals from these 

populations may contain adaptations 

that may be important to the taxon in 

the future. Lomolino and Channell 

(1998, p. 482) hypothesize that because 

peripheral populations should be 

adapted to a greater variety of 

environmental conditions, then they 

may be better suited to deal with 

anthropogenic (human-caused) 

disturbances than populations in the 

central part of a species’ range. Arctic 

grayling in the upper Missouri River 

have, for millennia, existed in a climate 

warmer than that experienced by the 

rest of the taxon. If this selective 

pressure has resulted in adaptations to 

cope with increased water temperatures, 

then the population segment may 

contain genetic resources important to 

the taxon. For example, if northern 

populations of Arctic grayling are less 

suited to cope with increased water 

temperatures expected under climate 

warming, then Missouri River Arctic 

grayling might represent an important 

population for reintroduction in those 

northern regions. We believe that Arctic 

grayling from the upper Missouri River’s 

occurrence at the southernmost extreme 

of the range contributes to its 

significance that may increased 

adaptability and contribute to the 

resilience of the overall taxon. 

Only Surviving Natural Occurrence of 

the Taxon that May be More Abundant 

Elsewhere as an Introduced Population 

Outside of its Historical Range 

This criterion does not directly apply 

to the Arctic grayling in the upper 

Missouri River because it is not the only 

surviving natural occurrence of the 

taxon; there are native Arctic grayling 

populations in Canada, Alaska, and 

Asia. That said, there are introduced 

Lake Dwelling Arctic Grayling within 

the native range in the Upper Missouri 

River System and Arctic grayling have 

been established in lakes outside their 

native range in Arizona, Colorado, 

Idaho, Montana, New Mexico, Utah, 

Washington, and Wyoming (Vincent 

1962, p. 15; Montana Fisheries 

Information System (MFISH) 2009; 

NatureServe 2010). 

Differs Markedly in Its Genetic 

Characteristics 

Differences in genetic characteristics 

can be measured at the molecular 

genetic or phenotypic level. Three 

different types of molecular markers 

(allozymes, mtDNA, and microsatellites) 

demonstrate that Arctic grayling from 

the upper Missouri River are genetically 

different from those in Canada, Alaska, 

and Asia (Everett 1986, pp. 79–80; 

Redenbach and Taylor 1999, p. 23; 

Stamford and Taylor 2004, p. 1538; 

Peterson and Ardren 2009, pp. 1764– 

1766; USFWS, unpublished data). These 

data confirm the reproductive isolation 

among populations that establishes the 

discreteness of Missouri River Arctic 

grayling under the DPS policy. Here, we 

speak to whether these data also 

establish significance. 

Allozymes 

Using allozyme electrophoretic data, 

Everett (1986, entire) found marked 

genetic differences among Arctic 

grayling collected from the Chena River 

in Alaska, those descended from fish 

native to the Athabasca River drainage 

in the Northwest Territories, Canada, 

and native upper Missouri River 

drainage populations or populations 

descended from them (see Leary 2005, 

pp. 1–2). The Canadian population had 

a high frequency of a unique isocitrate 

dehydrogenase allele (form of a gene) 

and a unique malate dehydrogenase 

allele, which strongly differentiated 

them from all the other samples (Everett 

1986, p. 44). With the exception one 

introduced population in Montana that 

is believed to have experienced extreme 

genetic bottlenecks, the Chena River 

(Alaskan) fish were highly divergent 

from all the other samples as they 

possessed an unusually low frequency 

of superoxide dismutase (Everett 1986, 

p. 60; Leary 2005, p. 1), and contained 

a unique variant of the malate 

dehydrogenase (Leary 2005, p. 1). 

Overall, each of the four native Missouri 

River populations examined (Big Hole, 

Miner, Mussigbrod, and Red Rock) 

exhibited statistically significant 

differences in allele frequencies relative 

to both the Chena River (Alaska) and 

Athabasca River (Canada) populations 

(Everett 1986, pp. 15, 67). 

Combining the data of Everett (1986, 

entire), Hop and Gharrett (1989, entire), 

and Leary (1990, entire) results in 


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information from 21 allozyme loci 

(genes) from the five native upper 

Missouri River drainage populations, 

five native populations in the Yukon 

River drainage in Alaska, and the one 

population descended from the 

Athabasca River drainage in Canada 

(Leary 2005, pp. 1–2). Examination of 

the genetic variation in these samples 

indicated that most of the genetic 

divergence is due to differences among 

drainages (29 percent) and 

comparatively little (5 percent) results 

from differences among populations 

within a drainage (Leary 2005, p. 1). 

Mitochondrial DNA 

Analysis using mtDNA suggest that 

Arctic grayling in North America 

represent at least three evolutionary 

lineages that are associated with distinct 

glacial refugia (Redenbach and Taylor 

1999, entire; Stamford and Taylor 2004, 

entire). Arctic grayling in the Missouri 

River basin belong to the so-called 

North Beringia lineage (Redenbach and 

Taylor 1999, pp. 27–28; Samford and 

Taylor 2004, pp. 1538–1540). Analysis 

of Arctic grayling using restriction 

enzymes and DNA sequencing indicated 

that the fish from the upper Missouri 

River drainage possessed, in terms of 

North American fish, an ancestral form 

of the molecule (different forms of 

mtDNA molecules are referred to as 

haplotypes) that was generally absent 

from populations collected from other 

locations within the species’ range in 

North America (Redenbach and Taylor 

1999, pp. 27–28; Stamford and Taylor 

2004, p. 1538). The notable exceptions 

were that some fish from the lower 

Peace River drainage in British 

Columbia, Canada (2 of 24 individuals 

in the population), and all sampled 

individuals from the Saskatchewan 

River drainage Saskatchewan, Canada (a 

total of 30 individuals from 2 

populations), also possessed this 

haplotype (Stamford and Taylor 2004, p. 

1538). 

Variation in mtDNA haplotypes based 

on sequencing a portion of the ‘control 

region’ of the mtDNA molecule of Arctic 

grayling from 26 different populations 

seems to support the groupings 

proposed by Stamford and Taylor (2004, 

entire) (USFWS unpublished data). Two 

haplotypes were common in the five 

native Missouri River populations (Big 

Hole, Red Rock, Madison, Miner, and 

Mussigbrod – total sample size 143 

individuals; USFWS unpublished data). 

Fish from three populations in 

Saskatchewan or near Hudson’s Bay 

also had one of these Missouri River 

haplotypes at very high frequency (50 of 

51 individuals sequenced had the same 

haplotype; USFWS unpublished data). 

The two ‘‘common’’ Missouri River 

haplotypes also occurred at low 

frequency in handful of other 

populations elsewhere in Canada and 

Alaska. For example, there a total of five 

such populations where a few 

individuals contained had one or the 

other of the two common Missouri River 

haplotypes (25 of 107 individuals 

sequenced; USFWS unpublished data). 

Also similar to the earlier study by 

Stamford and Taylor (2004, entire), a 

few individuals (9 of 40 individuals) 

from two populations from the Lower 

Peace River and the Upper Yukon River 

also had one or the other of the two 

common Missouri River haplotypes 

(USFWS unpublished data). 

The distribution of the common 

Missouri River haplotype compared to 

others suggested that Arctic grayling 

native to the upper Missouri River 

drainage probably originated from a 

glacial refuge in the drainage and 

subsequently migrated northwards 

when the Missouri River temporarily 

flowed into the Saskatchewan River and 

was linked to an Arctic drainage (Cross 

et al. 1986, pp. 374–375; Pielou 1991, p. 

195). When the Missouri River began to 

flow southwards because of the advance 

of the Laurentide ice sheet (Cross et al. 

1986, p. 375; Pileou 1991, p. 10), the 

Arctic grayling in the drainage became 

physically and reproductively isolated 

from the rest of the species’ range (Leary 

2005, p. 2; Campton 2006, p. 6), which 

would have included those populations 

in Saskatchewan. Alternatively, the 

Missouri River Arctic grayling could 

have potentially colonized 

Saskatchewan or the Lower Peace River 

(in British Columbia) or both postglacially (Stamford 2001, p. 49) via a 

gap in the Cordilleran and Laurentide 

ice sheets (Pielou 1991, pp. 10–11), 

which also might explain the low 

frequency of one or the other of the 

‘Missouri River’ haplotypes in grayling 

in the Lower Peace River and Upper 

Yukon River. 

We do not interpret the observation 

that Arctic grayling in Montana and 

Saskatchewan, and to lesser extent those 

from the Lower Peace and Upper Yukon 

River systems, share a mtDNA 

haplotype to mean that these groups of 

fish are genetically identical. Rather, we 

interpret it to mean that these fish 

shared a common ancestor tens to 

hundreds of thousands of years ago. 

Microsatellite DNA 

Recent analysis of microsatellite DNA 

(highly variable portions of nuclear 

DNA that exhibit tandem repeats of 

DNA base pairs) that included samples 

from five native Missouri River 

populations and two from 

Saskatchewan showed substantial 

divergence between these groups 

(Peterson and Ardren 2009, entire). 

Genetic differentiation between sample 

populations can be compared in terms 

of the genetic variation within relative 

to among populations, measured in 

terms of allele frequencies, a metric 

called Fst (Allendorf and Luikart 2007, 

pp. 52–54, 198–199). An analogous 

metric, named Rst, also measures genetic 

differentiation between populations 

based on microsatellite DNA, but differs 

from Fst in that it also considers the size 

differences between alleles (Hardy et al. 

2003, p. 1468). An Fst or Rst of 0 

indicates that populations are the same 

genetically (all genetic diversity within 

a species is shared by all populations), 

whereas a value of 1 indicates the 

populations are completely different (all 

the genetic diversity within a species is 

found as fixed differences among 

populations). Fst values ranged from 

0.13 to 0.31 (average 0.18) between 

Missouri River and Saskatchewan 

populations (Peterson and Ardren 2009, 

pp. 1758, 1764–1765), whereas Rst

values ranged from 0.47 to 0.71 (average 

0.54) for the same comparisons 

(Peterson and Ardren 2009, pp. 1758, 

1764–1765). This indicates that the two 

groups (Missouri vs. Saskatchewan 

populations) differ significantly in allele 

frequency and also in the size 

differences, and therefore divergence, 

among those alleles. This indicates that 

the observed genetic differences are not 

simply due to random loss of genetic 

variation because the populations are 

isolated (genetic drift), but they also are 

due to mutational differences, which 

suggests the groups may have been 

separated for millennia (Peterson and 

Ardren 2009, pp. 1767–1768). 

Comparison of 435 individuals from 

21 Arctic grayling populations from 

Alaska, Canada, and the Missouri River 

basin using nine of the same 

microsatellite loci as Peterson and 

Ardren (2009, entire) further supports 

the distinction of Missouri River Arctic 

grayling relative to populations 

elsewhere in North America (USFWS, 

unpublished data). A statistical analysis 

that determines the likelihood that an 

individual fish belongs to a particular 

group (e.g., STRUCTURE) (Pritchard et 

al. 2000, entire), clearly separated the 

sample fish from 21 populations into 

two clusters: one cluster representing 

populations from the upper Missouri 

River basin, and another cluster 

representing populations from across 

Canada and Alaska (USFWS, 

unpublished data). Factorial 

correspondence analysis (FCA) plots of 

individual fish also separated the fish 


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into two groups, or clouds of data points 

when visualized in a three-dimensional 

space (USFWS, unpublished data). The 

FCA is a multivariate data analysis 

technique used to simplify presentation 

of complex data and to identify 

systematic relations between variables, 

in this case the multi-locus genotypes of 

Arctic grayling. As with the other 

analysis, the FCA plots clearly 

distinguished Missouri River Arctic 

grayling from those native to Canada 

and Alaska (USFWS, unpublished data). 

Divergence in size among these alleles 

further supports the distinction between 

Missouri River grayling from those in 

Canada and Alaska (USFWS, 

unpublished data). The interpretation of 

these data is that the Missouri River 

populations and the Canada/Alaska 

populations are most genetically 

distinct at the microsatellite loci 

considered. 

Phenotypic Characteristics Influenced 

by Genetics—Meristics 

Phenotypic variation can be evaluated 

by counts of body parts (i.e., meristic 

counts of the number of gill rakers, fin 

rays, and vertebrae characteristics of a 

population) that can vary within and 

among species. These meristic traits are 

influenced by both genetics and the 

environment (Allendorf and Luikart 

2007, pp. 258–259). When the traits are 

controlled primarily by genetic factors, 

then meristic characteristics can 

indicate significant genetic differences 

among groups. Arctic grayling north of 

the Brooks Range in Alaska and in 

northern Canada had lower lateral line 

scale counts than those in southern 

Alaska and Canada (McCart and Pepper 

1971, entire). These two scale-size 

phenotypes are thought to correspond to 

fish from the North and South Beringia 

glacial refuges, respectively (Stamford 

and Taylor 2004, p. 1545). Arctic 

grayling from the Red Rock Lakes 

drainage had a phenotype intermediate 

to the large- and small-scale types 

(McCart and Pepper 1971, pp. 749, 754). 

Arctic grayling populations from the 

Missouri River (and one each from 

Canada and Alaska) could be correctly 

assigned to their group 60 percent of the 

time using a suite of seven meristic 

traits (Everett 1986, pp. 32–35). Those 

native Missouri River populations that 

had high genetic similarity also tended 

to have similar meristic characteristics 

(Everett 1986, pp. 80, 83). 

Arctic grayling from the Big Hole 

River showed marked differences in 

meristic characteristics relative to two 

populations from Siberia, and were 

correctly assigned to their population of 

origin 100 percent of the time (Weiss et 

al. 2006, pp. 512, 515–516, 518). The 

populations that were significantly 

different in terms of their meristic 

characteristics also exhibited differences 

in molecular genetic markers (Weiss et 

al. 2006, p. 518). 

Inference Concerning Genetic 

Differences in Arctic Grayling of the 

Missouri River Relative to Other 

Examples of the Taxon 

We believe the differences between 

Arctic grayling in the Missouri River 

and sample populations from Alaska 

and Canada measured using 

microsatellite DNA markers (Peterson 

and Ardren 2009, pp. 1764–1766; 

USFWS, unpublished data) represent 

‘‘marked genetic differences’’ in terms of 

the extent of differentiation (e.g., Fst, Rst) 

and the importance of that genetic 

legacy to the rest of the taxon. The 

presence of morphological 

characteristics separating Missouri River 

Arctic grayling from other populations 

also likely indicates genetic differences, 

although this conclusion is based on a 

limited number of populations (Everett 

1986, pp. 32–35; Weiss et al. 2006, 

entire), and we cannot entirely rule out 

the influence of environmental 

variation. 

The intent of the DPS policy and the 

ESA is to preserve important elements 

of biological and genetic diversity, not 

necessarily to preserve the occurrence of 

unique alleles in particular populations. 

In Arctic grayling of the Missouri River, 

the microsatellite DNA data indicate 

that the group is evolving 

independently from the rest of the 

species. The extirpation of this group 

would mean the loss of the genetic 

variation in one of the two most distinct 

groups identified in the microsatellite 

DNA analysis, and the loss of the future 

evolutionary potential that goes with it. 

Thus, the genetic data support the 

conclusion that Arctic grayling of the 

upper Missouri River represent a unique 

and irreplaceable biological resource of 

the type the ESA was intended to 

preserve. Thus, we conclude that 

Missouri River Arctic grayling differ 

markedly in their genetic characteristics 

relative to the rest of the taxon. 

Conclusion 

We find that a population segment 

that includes all native ecotypes of 

Arctic grayling in the upper Missouri 

River basin satisfies the discreteness 

standard of the DPS policy. The segment 

is physically isolated, and genetic data 

indicates that Arctic grayling in the 

Missouri River basin have been 

separated from other populations for 

thousands of years. The population 

segment occurs in an ocean drainage 

different from all other Arctic grayling 

populations worldwide, and we find 

that loss of this population segment 

would create a significant gap in the 

species’ range. Molecular genetic data 

clearly differentiate Missouri River 

Arctic grayling from other Arctic 

grayling populations, including those in 

Canada and Alaska. We conclude that 

because Arctic grayling of the upper 

Missouri River basin satisfy the criteria 

for being discrete and significant under 

our DPS policy, we determined that this 

population constitutes a DPS under our 

policy and the Act. 

In our stipulated settlement 

agreement, we also agreed to consider 

the appropriateness of distinct 

population segments based on the two 

different ecotypes (fluvial and adfluvial) 

expressed by native Arctic grayling of 

the upper Missouri River. We 

acknowledge there are cases where the 

Service has designated distinct 

population segments primarily on lifehistory even when they co-occur with 

another ecotype that can be part of the 

same gene pool (e.g., anadromous 

steelhead and resident rainbow trout, 

Oncorhynchus mykiss (71 FR 838, 

January 5, 2006). However, we conclude 

that designation of a single population 

segment for Arctic grayling in the upper 

Missouri River is more appropriate than 

designating two separate distinct 

population segments delineated by lifehistory type. In the Missouri River 

basin, the two ecotypes share a common 

evolutionary history, and do not cluster 

genetically based strictly on ecotype. As 

we discussed above, the fluvial and 

adfluvial life-history forms of Arctic 

grayling in the upper Missouri River do 

not appear to represent distinct 

evolutionary lineages. There appears to 

be some plasticity in behavior where 

individuals from a population can 

exhibit a range of behaviors. From a 

practical standpoint, we observe that 

only five native Arctic grayling 

populations remain in the Missouri 

River basin, and we believe that both 

fluvial and adfluvial native ecotypes 

have a role in the conservation of the 

larger population segment. We believe 

that the intent of the ESA and the DPS 

policy, and our obligation to assess the 

appropriateness of alternate DPS 

designations in the settlement 

agreement are best served by 

designating a single distinct population 

segment, rather than multiple 

population segments. 

As we described above, we are not 

including introduced populations that 

occur in lakes in the Upper Missouri 

River basin in the DPS. The Service has 

interpreted the Act to provide a 

statutory directive to conserve species 

in their native ecosystems (49 FR 33890, 


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August 27, 1984) and to conserve 

genetic resources and biodiversity over 

a representative portion of a taxon’s 

historical occurrence (61 FR 4723, 

February 7, 1996). The introduced 

Arctic grayling occur in lakes apart from 

native fluvial environments and from 

lakes where native adfluvial grayling 

occur. These introduced populations 

have not been used for any conservation 

purpose and could pose genetic risks to 

the native Arctic grayling population. 

We find that the Arctic grayling of the 

upper Missouri River basin constitute a 

distinct population segment. We define 

the historical range of this population 

segment to include the major streams, 

lakes, and tributary streams of the upper 

Missouri River (mainstem Missouri, 

Smith, Sun, Beaverhead, Jefferson, Big 

Hole, and Madison Rivers, as well as 

their key tributaries, as well as a few 

small lakes where Arctic grayling are or 

were believed to be native (Elk Lake, 

Red Rock Lakes, Miner Lake, and 

Mussigbrod Lake, all in Beaverhead 

County, Montana). We define the 

current range of the DPS to consist of 

extant native populations in the Big 

Hole River, Miner Lake, Mussigbrod 

Lake, Madison River–Ennis Reservoir, 

and Red Rock Lakes. We refer to this 

DPS as the native Arctic grayling of the 

upper Missouri River. The remainder of 

this finding will thus focus on the 

population status of and threats to this 

entity. 

Population Status and Trends for 

Native Arctic Grayling in the Upper 

Missouri River 

We identified a DPS for Arctic 

grayling in the upper Missouri River 

basin that includes five extant 

populations: (1) Big Hole River, (2) 

Miner Lake, (3) Mussigbrod Lake, (4) 

Madison River-Ennis Reservoir, and (5) 

Red Rock Lakes. In general, we 

summarize what is known about the 

historical distribution and abundance of 

each of these populations, describe their 

current distributional extent, summarize 

any available population monitoring 

data, identify the best available 

information that we use to infer the 

current population status, and 

summarize the current population status 

and trends. 

TABLE 4. EXTENT AND CURRENT ESTIMATED EFFECTIVE POPULATION SIZES (Ne) OF NATIVE ARCTIC GRAYLING

POPULATIONS IN THE MISSOURI RIVER BASIN. VALUES IN PARENTHESES REPRESENT 95 PERCENT CONFIDENCE INTERVALS. 

Estimated Adult Population Size Assuming: 

Population Name Population Extenta Ne b Biological Date of 

Population Size c Ne/N ratio 0.25 d Ne/N ratio 0.14 e

Big Hole River 158 mi 208 (176 to 251) 2000–2003 828 (704 to 1,004) 1,486 (1,257 to 1,793) 

Miner Lakes 26.9 ha 286 (143 to 4,692) 2001–2003 1,144 (572 to 18,768) 2,043 (1,021 to 33,514) 

Mussigbrod Lake 42.5 ha 1,497 (262 to ∞) 2001–2003 5,988 (1,048 to ∞) 10,693 (1,871 to ∞) 

Madison River–Ennis 

Reservoir 1,469 ha 162 (76 to ∞) 1991–1993 648 (304 to ∞) 1,157 (543 to ∞) 

Red Rock Lakes 890 ha 228 (141 to 547) 2000–2002 912 (564 to 2,188) 1,629 (1,007 to 3,907) 

a Approximate maximum spatial extent over which Arctic grayling are encountered in a given water. b Effective population size estimates from Peterson and Ardren (2009, p.1767). Confidence intervals that include infinity (∞) can result from 

statistical artifacts of the linkage disequilibrium method (Waples and Do 2007, p. 10; Russell and Fewster 2009, pp. 309–310). The usual interpretation is that there is no evidence for any disequilibrium caused by genetic drift due to a finite number of parents—it can all be explained by 

sampling error (Waples and Do 2007, p. 10). Thus, the effective size is infinitely large. Small sample sizes may influence estimates in some 

cases (e.g., Madison River-Ennis Reservoir). c Approximate date to which the Ne estimate refers. For example, Ne for the Big Hole River based on genotyping a sample of fish from 2005– 

2006, but the interpretation of Ne is the number of breeding adults that produced the fish in the observed sample. Thus the true biological date of 

the Ne estimate is one generation before 2005–2006, or approximately 2000–2003. d Adult population size estimated from Ne assuming Ne /N = 0.25. This value was the midpoint of a range of values (0.2–0.3) commonly cited 

for Ne /N ratios in salmonid fishes (Allendorf et al. 1997, p. 143; McElhahey et al. 2000, p. 63; Rieman and Allendorf 2001, p. 762; Palm et al. 

2003, p. 260). e Adult population size estimated from Ne assuming Ne /N = 0.14. This value was the median Ne /N ratio based on a meta analysis of 83 studies for 65 different species (Palstra and Ruzzante 2008, p. 3428). 

Big Hole River 

Historically, Arctic grayling 

presumably had access to and were 

distributed throughout much of the Big 

Hole River, including the lower reaches 

of many tributary streams, such as Big 

Lake, Deep, Doolittle, Fishtrap, Francis, 

Governor, Johnson, LaMarche, Miner, 

Mussigbrod, Odell, Pintlar, Rock, Sand 

Hollow, Swamp, Seymour, Steel, 

Swamp, and Wyman Creeks, as well as 

the Wise River (Liknes 1981, p. 11; 

Liknes and Gould 1987, p. 124; Kaya 

1990, pp. 36–40). Presently, Arctic 

grayling are found primarily in the 

mainstem Big Hole River between the 

towns of Glen and Jackson, Montana, a 

distance of approximately 181 river km 

(113 mi), and in 11 tributaries, totaling 

an additional 72 river km (45 mi) 

(Magee 2010a, pers. comm.; see Table 4 

above). The total current maximum 

extent of Arctic grayling occurrence in 

the Big Hole River is approximately 250 

river km (156 mi). However, the fish are 

not continuously distributed across this 

distance, and instead tend to be 

concentrated in discrete patches (Magee 

et al. 2006, pp. 27–28; Rens and Magee 

2007, p. 15) typically associated with 

spawning and rearing habitats or coldwater sites that provide a thermal refuge 

from high summer water temperatures. 

Kaya (1992, pp. 50–52) noted the 

general lack of monitoring data for the 

Big Hole River fluvial Arctic grayling 

population prior to the late 1970s, but 

data collected since that time indicate 

the overall range has contracted over the 

last 2 decades. During 1978 and 1979 

Arctic grayling were observed in 

Governor Creek (in the headwaters of 

the Big Hole River) and downstream in 

the Big Hole River near Melrose, 

Montana (Liknes 1981, p. 11). Arctic 

grayling have not recently been 

encountered in Governor Creek (Rens 

and Magee 2007, p. 15; Montana Fish, 

Wildife and Parks (MFWP), 

unpublished data), but are occasionally 


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encountered in the Big Hole River 

downstream of Divide, Montana, at very 

low densities and as far downstream as 

Melrose or Glen, Montana (Oswald 

2005a, pers. comm.). More recently, 

Arctic grayling have become less 

abundant in historical spawning and 

rearing locations in the upper watershed 

near Wisdom, Montana, and also in 

downstream river segments with deep 

pool habitats considered important for 

overwintering (Magee and Lamothe 

2003, pp. 18–21; MFWP unpublished 

data). Comparatively, greater numbers of 

Arctic grayling are encountered in the 

lower reaches of tributaries to the upper 

Big Hole River, including LaMarche, 

Fishtrap, Steel, and Swamp Creeks 

(Rens and Magee 2007, p. 13). 

Based on the best available data, the 

adult population declined by one half 

between the early 1990s and the early 

2000s (see Figure 3, USFWS 

unpublished data), which is equivalent 

to a decline of 7 percent per year, on 

average. Monitoring data collected by 

MFWP also support the conclusion that 

the Arctic grayling population in the Big 

Hole River declined during this time 

period (Byorth 1994a, p. 11; Rens and 

Magee 2007, entire; MFPW, 

unpublished data). 

FIGURE 3. Effective population size 

(Ne) of Big Hole River Arctic grayling 

based on microsatellite DNA genotypes 

from fish collected in three time periods 

(USFWS, unpublished data). The Ne are 

estimated using the linkage 

disequilibrium method of Waples and 

Do (2008, entire), and error bars 

represent 95% confidence intervals 

estimated by the jackknife method. 

Miner Lakes 

The Miner Lakes are a complex of 

small lakes in the upper Big Hole River 

drainage. Lower Miner Lakes are two 

small lakes in the middle of the Miner 

Creek drainage connected by a narrow 

section approximately 100 m (330 ft) in 

length, functionally representing a 

single lake for fish populations. Arctic 

grayling occur in Lower Miner Lakes 

(hereafter Miner Lakes population), 

which has a total surface area of 26.7 

hectares (ha) or 0.267 km2 (66 acres 

(ac)). Arctic grayling primarily reside in 

the lake, and presumably move into the 

inlet or outlet tributary to spawn. 

Surveys conducted upstream and 

downstream of the Lower Miner Lakes 

in 1992 and 1994, respectively, captured 

no Arctic grayling (Downing 2006, pers. 

comm.). Apparently, adults do not 

remain in the stream long after 

spawning and young-of-the-year (YOY) 

move into Lower Miner Lakes. 

The MFWP conducted limited 

surveys in Lower Miner Lakes, but the 

abundance of the population has not 

been estimated by traditional fishery 

methods. Arctic grayling are classified 

as ‘‘common’’ in Lower Miner Lakes 

(MFISH 2010). Introduced brook trout 

also are present. 

The best available information on the 

abundance of Miner Lakes Arctic 

grayling comes from a genetic 

assessment of that population. Based on 

a sample of fish from 2006, Peterson and 

Ardren (2009, p. 1767) estimated an 

effective population size of 286. This 

estimate represents an approximation of 

abundance of breeding adults at a single 

point in time, and there are no data on 

which to base an assessment of the 

population trend. 

Mussigbrod Lake 

Mussigbrod Lake has a surface area of 

42.5 ha (105 ac), and is found in the 

middle reaches of Mussigbrod Creek, a 

tributary to the North Fork Big Hole 

River. Arctic grayling primarily reside 

in the lake. We do not know whether 

Arctic grayling spawn in the inlet 

stream or within the lake (Magee and 


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Olsen 2010, pers. comm.). Arctic 

grayling occasionally pass over a 

diversion structure downstream at the 

outlet of Mussigbrod Lake, and become 

trapped in a pool that is isolated 

because of stream dewatering. The 

MFWP periodically capture grayling in 

this pool and return them to the lake. 

Data for the Mussigbrod Lake 

population of Arctic grayling is 

minimal. The MFWP has conducted 

very limited surveys and the abundance 

of the population has not been 

estimated by traditional fishery 

methods. Genetic data indicate that 

Arctic grayling are comparatively 

abundant (see Table 4 above). Based on 

a sample from 2006, Peterson and 

Ardren (2009, p. 1767) estimated an 

effective size of 1,497. The best 

available data indicate that the 

Mussigbrod Lake population is 

comparatively large, but we have no 

data about the population trend. 

Madison River – Ennis Reservoir 

Historically, Arctic grayling were 

reported to be abundant in the middle 

and upper Madison River, but have 

undergone a dramatic decline in the 

past 100 years with the species 

becoming rare by the 1930s (Vincent 

1962, pp. 11, 85–87). Native Arctic 

grayling are thought be extirpated from 

the upper Madison River. A major 

impact to fish in that area was the 

construction of Hebgen Dam, which 

flooded Horsethief Springs, a small 

tributary that was reportedly one of the 

most important streams for Arctic 

grayling (Vincent 1962, pp. 40–41, 128). 

In the middle Madison River, Arctic 

grayling were apparently common to 

plentiful in the mainstem River near 

Ennis, Montana, and some associated 

tributaries (Jack, Meadow, and O’Dell 

Creeks) (Vincent 1962, p. 128). In 1906, 

construction of Ennis Dam blocked all 

upstream movement of fishes, and 

apparently had a large negative effect on 

Arctic grayling. Vincent (1962) noted 

that ‘‘early settlers reported scooping up 

boxes full of grayling at the base of 

Ennis Dam the year after it was 

constructed’’ (p. 128), and that the 

species apparently became quite rare by 

the late 1930s (Vincent 1962, p. 85). 

The current distribution of Arctic 

grayling in the Madison River is 

primarily restricted to the Ennis 

Reservoir and upstream into the river 

approximately 6.5 km (approximately 4 

mi) to the Valley Garden Fishing Access 

Site (Byorth and Shepard 1990, p. 21). 

Arctic grayling are occasionally 

encountered in the Madison River 

downstream and upstream from Ennis 

Reservoir (Byorth and Shepard 1990, p. 

25; Clancey 2004, p. 22; 2008, p. 21). 

Arctic grayling migrate from the 

reservoir into the river to spawn, then 

return to the reservoir (Byorth and 

Shepard 1990, pp. 21–22; Rens and 

Magee 2007, pp. 20–21). The YOY 

Arctic grayling spawned in the Madison 

River migrate downstream into Ennis 

Reservoir about 1 month after 

emergence, but while they are in the 

river, they are typically encountered in 

backwater or slackwater habitat (Jeanes 

1996, pp. 31–34). 

The MFWP has sporadically 

monitored Arctic grayling in the 

Madison River near Ennis Reservoir 

since about 1990. Despite sparse data, 

declining catches for both spawning 

adults and YOY indicate the population 

is less abundant now compared to the 

early 1990s. The highest numbers of 

YOY Arctic grayling were encountered 

in the early 1990s, and no more than 

two have been captured in any given 

year since that time. Our interpretation 

of this information is that Arctic 

grayling in the Madison River–Ennis 

Reservoir population have declined 

during the past 20 years and are 

presently at very low abundance. 

Abundance of the Madison River– 

Ennis Reservoir Arctic grayling has been 

estimated twice. In 1990, the adult 

population was estimated to be 545, but 

the authors cautioned that the accuracy 

of the estimate was questionable as it 

was based on recapturing only. From a 

sample of fish collected mostly in 1996, 

the effective size of the population 

(breeding adults) was estimated as 162 

(Peterson and Ardren 2009, p. 1767). 

The average number of Arctic grayling 

captured per unit effort (CPUE) declined 

by approximately a factor of 10 between 

the early 1990s and recent samples 

(Clancey 1998, p. 10; Clancey 2007, 

p.16; Clancey 2008, pp. ii, 21, A2-2; 

Clancey and Lohrenz 2009, pp. 30, B2; 

Clancey 2010a, pers. comm.; Clancey 

2010b, pers. comm.). Adult Arctic 

grayling may currently exist at only 10 

to 20 percent of the abundance observed 

in the early 1990s. Based on the best 

available data, we conclude that this 

Arctic grayling population has been in 

a decline during the past 20 years and 

may only consist of a few hundred 

adults. 

Red Rocks Lakes 

Arctic grayling are native to waters of 

the upper Beaverhead River system, 

including the Red Rock River drainage. 

During the past 50 to 100 years, both the 

distribution and abundance of Arctic 

grayling in the Centennial Valley, 

Beaverhead County, Montana (which 

contains the Red Rock River), has 

severely declined (Vincent 1962, pp. 

115–121; Unthank 1989, pp. 13–17; 

Mogen 1996, pp. 2–5, 75–84). As of 

about 50 years ago, Arctic grayling 

spawned in at least 12 streams in the 

Centennial Valley (Mogen 1996, p. 17), 

but they appear to have been extirpated 

from all but 2 streams (Boltz 2006, p. 6). 

Presently, Arctic grayling spawn in two 

locations within the Red Rock River 

drainage: Odell Creek, a tributary to 

Lower Red Rock Lake; and Red Rock 

Creek, the primary tributary to Upper 

Red Rock Lake (Mogen 1996, pp. 47–48; 

Boltz 2006, p. 1). Lower and Upper Red 

Rock Lakes are connected by a short 

segment of river, and both lakes are 

contained within the boundaries of the 

Red Rock Lakes National Wildlife 

Refuge (NWR). The upper lake appears 

to be the primary rearing and 

overwintering habitat for Arctic 

grayling. Red Rock Creek is the only 

stream where Arctic grayling spawn in 

appreciable numbers (Mogen 1996, pp. 

45–48). Collectively, we refer to this 

population as the Red Rocks Lakes 

Arctic grayling, and characterize it as 

having the adfluvial ecotype. 

Arctic grayling in the Red Rock Lakes 

have been monitored intermittently 

since the 1970s. Most of that effort 

focused on Red Rock Creek, but periodic 

sampling also occurred in Odell Creek. 

The MFWP and the Service occasionally 

sampled for Arctic grayling in Odell 

Creek, where grayling abundance 

declined over the past few decades. On 

average, the minimum sizes of the 

spawning runs in Red Rock Creek since 

1994 are about half of those recorded 4 

decades ago (i.e., 623 vs. 308 per year) 

(data summarized from Mogen 1996, p. 

70 and Boltz 2006, p. 7). The spawning 

runs into Red Rock Creek fluctuated 

during the 1990s and early 2000s, but 

about 450 or fewer adult Arctic grayling 

have been captured in 6 of 7 years in 

which weirs traps were operated. 

Electrofishing surveys conducted in Red 

Rock Creek by MFWP seem to 

corroborate a decline in the spawning 

population, as total catches decreased 

even as sampling effort increased (Rens 

and Magee 2007, pp. 16–18). 

Based on a sample of fish from Red 

Rock Creek in 2005, Peterson and 

Ardren (2009, pp. 1761, 1767) estimated 

an effective size of 228, which is 

interpreted as the number of breeding 

adults that produced the fish sampled in 

2005. The best available data indicate 

that the Red Rock Lakes Arctic grayling 

population has declined over the past 2 

decades. 

Population viability analysis (PVA) of 

native Missouri River Arctic grayling 

To gauge the probability that the 

different native populations of Arctic 

grayling in the upper Missouri River 


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basin will go extinct from unpredictable 

events in the foreseeable future, we 

conducted a simple population viability 

analysis (PVA) (see Dennis et al. (1991, 

entire) in Morris and Doak 2002, pp. 85– 

87 for details on the PVA model and the 

software code to run the model). We 

assumed that a population with 50 or 

fewer adults is likely influenced by 

demographic stochasticity (chance 

variation in the fates of individuals 

within a given year) and genetic 

stochasticity (random changes in a 

population’s genetic makeup), and 

would not be expected to persist long as 

a viable population. For the different 

PVA scenarios, we assume either the 

population has stabilized, or the 

estimated decline will continue at a 

constant rate. 

We considered the probability of 

extinction individually by population, 

as populations appear to be 

reproductively isolated. The relative 

risk of extinction in the foreseeable 

future (30 years based on the 

observation that the variability in 

predictions for extinction risk from the 

PVA model increases substantially after 

30 years) varies among the different 

populations, with the largest 

population, Mussigbrod Lake, having a 

very low probability of extinction (less 

than 1 percent) in the foreseeable future, 

even given a population decline. The 

other four populations have 

comparatively greater probabilities of 

extinction in the foreseeable future, 

with all being roughly similar in 

magnitude (13-55 percent across 

populations) when considering only 

stochastic (random or chance) 

processes. The Madison River has the 

greatest probability of extinction by 

stochastic processes (36-55 percent), 

followed by Big Hole (33-42 percent), 

Red Rocks (31-40 percent), and Miner 

(13-37 percent). 

Overall, the PVA analyses indicate 

that four populations (Madison, Big 

Hole, Red Rocks, and Miner) appear to 

be at risk from chance environmental 

variation because of low population 

abundance. This is a general conclusion, 

and the actual risk may vary 

substantially among populations 

(USFWS unpublished data). For 

example, Arctic grayling in the Big Hole 

River population spawn in different 

locations, which would reduce the risk 

that an environmental catastrophe 

would simultaneously kill all breeding 

adults, relative to a situation where 

adults appear to be primarily in a single 

location or reach of river (e.g., Red 

Rocks and Madison populations). 

Arctic Grayling Conservation Efforts 

Native Arctic Grayling Genetic Reserves 

and Translocation 

Given concern over the status of 

native Arctic grayling, the Montana 

Arctic Grayling Recovery Program 

(AGRP) was formed in 1987, to address 

conservation concerns for primarily the 

fluvial ecotype in Big Hole River, and to 

a lesser extent the native adflvuial 

population in Red Rock Lakes 

(Memorandum of Understanding (MOU) 

2007, p. 2). The AGW was established 

as an ad hoc technical workgroup of the 

AGRP. In 1995, the AGW finalized a 

restoration plan that outlined an agenda 

of restoration tasks and research, 

including management actions to secure 

the Big Hole River population, brood 

stock development, and a program to reestablish four additional fluvial 

populations (AGW 1995, pp. 7–17). 

Consequently, the State of Montana 

established genetic reserves of Big Hole 

River grayling (Leary 1991, entire), and 

has used the progeny from those 

reserves in efforts to re-establish 

additional fluvial populations within 

the historical native range in the 

Missouri River basin (Rens and Magee 

2007, pp. 21–38). Currently, brood 

(genetic) reserves of Big Hole River 

grayling are held in two closed-basin 

lakes in south-central Montana (Rens 

and Magee 2007, p. 22). These fish are 

manually spawned to provide gametes 

for translocation efforts in Montana 

(Rens and Magee 2007, p. 22). 

Functionally, these brood reserves are 

hatchery populations maintained in a 

natural setting, and we do not consider 

them wild populations for the purposes 

of evaluating the status of native Arctic 

grayling in the Missouri River basin. 

However, they are important to recovery 

efforts. 

For more than 13 years, MFWP has 

attempted to re-establish populations of 

fluvial Arctic grayling in various 

locations in the Missouri River basin, 

including the Ruby, Sun, Beaverhead, 

Missouri, Madison, Gallatin, and 

Jefferson Rivers (Lamothe and Magee 

2004a, pp. 2, 28). A self-sustaining 

population has not yet been established 

from these reintroductions (Lamothe 

and Magee 2004a, p. 28; Rens and 

Magee 2007, pp. 35–36, 38). Recent 

efforts have focused more intensively on 

the Ruby and Sun Rivers, and have used 

methods that should improve 

reintroduction success (Rens and Magee 

2007, pp. 24–36). Encouragingly, natural 

reproduction by Arctic grayling in the 

Ruby River was confirmed during fall 

2009 (Magee 2010b, pp. 6–7, 22). 

Monitoring will continue in subsequent 

years to determine whether the 

population has become a stable and 

viable population, as defined by the 

guidance and implementation 

documents of the translocation 

programs (AGW 1995, p. 1; 

Memorandum of Agreement (MOA) 

1996, p. 2). Consequently, we do not 

consider the Ruby River to represent a 

self-sustaining population for the 

purposes of evaluating the population 

status of Missouri River grayling in this 

finding. Arctic grayling presumably 

from previous translocations are 

occasionally encountered near 

translocation sites in other waters (Rens 

and Magee 2007, pp. 35–38; MFWP, 

unpublished data). There is no evidence 

that these individuals represent progeny 

from a re-established population, so we 

cannot consider them elements of a 

stable and viable population for the 

purposes of evaluating the population 

status of Missouri River Arctic grayling 

in this finding. 

Big Hole River Candidate Conservation 

Agreement with Assurances 

On August 1, 2006, the Service issued 

ESA section 10(a)(1)(A) enhancement of 

survival permit (TE-104415-0) to 

Montana Fish, Wildlife and Parks 

(MFWP) to implement a Candidate 

Conservation Agreement with 

Assurances for Arctic grayling in the 

upper Big Hole River (Big Hole Grayling 

CCAA) (MFWP et al. 2006, entire). This 

permit is valid through August 1, 2026. 

The goal of the Big Hole Grayling CCAA 

is to secure and enhance a population 

of fluvial Arctic grayling within the 

upper reaches of their historic range in 

the Big Hole River drainage by working 

with non-Federal property owners to 

implement conservation measures on 

their lands. The guidelines of this CCAA 

will be met by implementing 

conservation measures that improve 

stream flows, protect and restore 

riparian habitats, identify and reduce or 

eliminate entrainment (inadvertent 

capture) of grayling in irrigation ditches, 

and remove human-made barriers to 

grayling migration (MFWP et al. 2006, 

p. 3). Currently, 32 landowners 

representing 64,822 ha (160,178 ac) in 

the upper Big Hole River drainage are 

participating in the CCAA (Lamothe 

2009, p. 5). The MFWP leads the Big 

Hole Grayling CCAA implementation 

effort, and is supported by Montana 

Department of Natural Resources and 

Conservation (MDNRC), USDA Natural 

Resources Conservation Service (NRCS), 

and the Service. Other groups helping 

implement the CCAA include the Big 

Hole Watershed Committee, the Big 

Hole River Foundation, Montana Trout 

Unlimited, the Western Water Project 

(affiliated with Trout Unlimited), and 


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The Nature Conservancy (Lamothe 

2008, p. 23). Detailed information on 

conservation actions and restoration 

projects implemented under the plan 

are available in various reports (AGW 

2010, p. 4; Everett 2010, entire; Lamothe 

et al. 2007, pp. 6–35; Lamothe 2008, pp. 

7–21; Lamothe 2009, entire; Lamothe 

2010, entire; Magee 2010b, entire; 

Roberts 2010, entire). 

Biological Effectiveness of the Ongoing 

Conservation Programs 

The current and anticipated effects of 

the aforementioned conservation 

programs on the biological status and 

threats to Arctic grayling of the upper 

Missouri River are discussed elsewhere 

in the document (see Summary of 

Information Pertaining to the Five 

Factors and Finding sections, below). 

We continue to encourage and promote 

collaborative efforts to secure existing 

populations, and to increase the 

distribution of the Arctic grayling 

within its historical range in the upper 

Missouri River basin. 

Summary of Information Pertaining to 

the Five Factors 

Section 4 of the ESA (16 U.S.C. 1533) 

and implementing regulations (50 CFR 

424) set forth procedures for adding 

species to the Federal Lists of 

Endangered and Threatened Wildlife 

and Plants. Under section 4(a)(1) of the 

ESA, a species may be determined to be 

endangered or threatened based on any 

of the following five factors: (A) The 

present or threatened destruction, 

modification, or curtailment of its 

habitat or range; (B) overutilization for 

commercial, recreational, scientific, or 

educational purposes; (C) disease or 

predation; (D) the inadequacy of 

existing regulatory mechanisms; or (E) 

other natural or manmade factors 

affecting its continued existence. In 

making this finding, information 

pertaining to the Missouri River DPS of 

Arctic grayling in relation to the five 

factors provided in section 4(a)(1) of the 

Act is discussed below. 

In considering what factors might 

constitute threats to a species, we must 

look beyond the exposure of the species 

to a factor to evaluate whether the 

species may respond to the factor in a 

way that causes actual impacts to the 

species. If there is exposure to a factor 

and the species responds negatively, the 

factor may be a threat and we attempt 

to determine how significant a threat it 

is. The threat is significant if it drives, 

or contributes to, the risk of extinction 

of the species such that the species 

warrants listing as endangered or 

threatened as those terms are defined in 

the Act. 

A. The Present or Threatened 

Destruction, Modification, or 

Curtailment of Its Habitat or Range 

Curtailment of Range and Distribution 

The number of river kilometers 

(miles) occupied by the fluvial ecotype 

of Arctic grayling in the Missouri River 

has been reduced by approximately 95 

percent during the past 100 to 150 years 

(Kaya 1992, p. 51). The fluvial life 

history is only expressed in the 

population residing in the Big Hole 

River; the remnant population in the 

Madison River near Ennis Reservoir has 

apparently diverged toward an adfluvial 

life history. Arctic grayling distribution 

within the Centennial Valley in the 

upper Beaverhead River also has been 

severely curtailed during the last 50 to 

100 years, such that the only remaining 

example of the species in that drainage 

is an adfluvial population associated 

with the Red Rock Lakes. Indigenous 

populations in the Big Hole River, 

Madison River, and Red Rock Lakes all 

exist at reduced densities on both 

contemporary and historical timescales. 

The Miner Lakes and Mussigbrod Lake 

populations appear to have been 

reproductively isolated for hundreds of 

years (USFWS, unpublished data), so a 

restricted distribution may represent the 

natural historical condition for these 

populations. The curtailment of range 

and distribution is a current threat, 

because the probability of extirpation of 

the DPS is related to the number of 

populations and their resilience. Since 

the DPS currently exists as a set of 

generally small, isolated populations 

that cannot naturally re-found or 

‘rescue’ another population. Thus, the 

curtailment of range and distribution 

will remain a threat in the foreseeable 

future, absent the reestablishment of 

additional populations within the DPS’ 

historical range. Reintroduction 

attempted under the auspices of the 

1995 Restoration Plan (AGW 1995, 

entire) have been underway since 1997, 

but have not yet resulted in reestablishment of populations or the 

expansion of the DPS’ current range. 

Dams on Mainstem Rivers 

The majority of the historical range of 

the Upper Missouri River DPS of Arctic 

grayling has been altered by the 

construction of dams and reservoirs that 

created barriers obstructing migrations 

to spawning, wintering, or feeding areas; 

inundated grayling habitat; and 

impacted the historical hydrology of 

river systems (Kaya 1990, pp. 51–52; 

Kaya 1992, p. 57). The construction of 

large dams on mainstem river habitats 

throughout the upper Missouri River 

system fragmented river corridors 

necessary for the expression of 

migratory life histories. Construction of 

dams that obstructed fish passage on the 

mainstem Missouri River (Hauser, 

Holter, Canyon Ferry, and Toston), 

Madison River (Madison–Ennis, 

Hebgen), Beaverhead River and its 

tributary Red Rock River (Clark Canyon, 

Lima), Ruby River (Ruby), and Sun 

River (Gibson) all contributed to the 

rangewide decline of this DPS (Vincent 

1962, pp. 127–128; Kaya 1992, p. 57; see 

Figure 2). 

Dams also may continue to impact the 

extant population in the Madison River. 

The Madison Dam (also known as Ennis 

Dam), as with the aforementioned dams, 

is a migration barrier with no fish 

passage facilities. Anglers have reported 

encountering Arctic grayling in pools 

below the dam, implying that fish 

occasionally pass (downstream) over or 

through the dam. These fish would be 

‘‘lost’’ to the population residing above 

the dam because they cannot return 

upstream, but have apparently not 

established populations downstream. 

Operational practices of the Madison 

Dam also have been shown to affect the 

resident fishes. A population decline of 

Arctic grayling coincided with a 

reservoir drawdown in winter 1982– 

1983 that was intended to reduce the 

effects of aquatic vegetation on the 

hydroelectric operations at the dam 

(Byorth and Shepard 1990, pp. 52–53). 

This drawdown likely affected the 

forage base, rearing habitat, and 

spawning cycle of Arctic grayling in the 

reservoir. 

The presence of mainstem dams is a 

historical, current, and future threat to 

the DPS. Lack of fish passage at these 

dams contributed to the extirpation of 

Arctic grayling from some waters by 

blocking migratory corridors (Vincent 

1962, p. 128), curtailing access to 

important spawning and rearing 

habitats, and impounding water over 

former spawning locations (Vincent 

1962, p. 128). These dams are an 

impediment to fish migration and limit 

the ability of fish to disperse between 

existing populations or recolonize 

habitat fragments, and will continue to 

act in this manner for the foreseeable 

future. We believe the presence of a 

mainstem dam is an immediate and 

imminent threat to the Madison River 

population, as the remaining grayling 

habitat is adjacent to Ennis Dam (see 

Figure 2). We not aware of any plans to 

retrofit the Ennis Dam or any other 

mainstem dam to provide upstream fish 

passage, so we expect the current 

situation to continue. The Federal 

Energy Regulatory Commission (FERC) 

license for hydroelectric generation at 

Ennis Dam will not expire until the year 


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2040 (FERC 2010, entire). The upper 

Missouri River basin dam having the 

FERC license with the latest expiration 

date is Clark Canyon Dam, which will 

not expire until 2059 (FERC 2010, 

entire). Thus, mainstem dams will 

remain a threat in the foreseeable future, 

which is 30 to 50 years based on the 

duration of existing FERC licenses in 

the upper basin. 

Agriculture and Ranching 

The predominant use of private lands 

in the upper Missouri River basin is 

irrigated agriculture and ranching, and 

these activities had and continue to 

have significant effects on aquatic 

habitats. In general, these effects relate 

to changes in water availability and 

alteration to the structure and function 

of aquatic habitats. The specific 

activities and their impacts are 

discussed below. 

Smaller Dams and Fish Passage Barriers 

Smaller dams or diversions associated 

with irrigation structures within specific 

watersheds continue to pose problems 

to Arctic grayling migratory behavior, 

especially in the Big Hole River 

drainage. In the Big Hole River, 

numerous diversion structures have 

been identified as putative fish 

migration barriers (Petersen and 

Lamothe 2006, pp. 8, 12–13, 29) that 

may limit the ability of Arctic grayling 

to migrate to spawning, rearing, or 

sheltering habitats under certain 

conditions. The Divide Dam on the Big 

Hole River near the town of Divide, 

Montana, has existed for nearly 80 years 

and is believed to be at least a partial 

barrier to upstream movement by fishes 

(Kaya 1992, p. 58). As with the larger 

dams, these smaller fish passage barriers 

can reduce reproduction (access to 

spawning habitat is blocked), reduce 

growth (access to feeding habitat is 

blocked), and increase mortality (access 

to refuge habitat is blocked). A number 

of planned or ongoing conservation 

actions to address connectivity issues 

on the Big Hole River and its tributaries 

may reduce the threat posed by 

movement barriers for Arctic grayling in 

that habitat. The Divide Dam is being 

replaced with a new structure that 

provides fish passage, and construction 

began in July 2010 (Nicolai 2010, pers. 

comm.). At least 17 fish ladders have 

been installed at diversion structures in 

the Big Hole River since 2006 as part of 

the Big Hole Grayling CCAA (AGW 

2010, p. 4), and a culvert barrier at a 

road crossing on Governor Creek 

(headwaters of Big Hole River) was 

replaced with a bridge that is expected 

to provide upstream passage for aquatic 

organisms under all flow conditions 

(Everett 2010, pp. 2–6). Non-Federal 

landowners who control approximately 

50 to 70 percent of the points of 

irrigation diversion in the upper Big 

Hole River are enrolled in the CCAA 

(Roberts and Lamothe 2010, pers. 

comm.), so the threats posed by fish 

passage barriers should be substantially 

reduced in the Big Hole River during the 

next 10 to 20 years (foreseeable future) 

based on the minimum duration of sitespecific plans for landowners enrolled 

in the CCAA and the duration of the 

ESA section 10(a)(1)(A) enhancement of 

survival permit (TE 104415-0) 

associated with the CCAA (MFWP et al. 

2006, p. 75). 

Fish passage barriers also have been 

noted in the Red Rock Lakes system 

(Unthank 1989, p. 9). Henshall (1907, p. 

5) noted that spawning Arctic grayling 

migrated from the Jefferson River 

system, through the Beaverhead River 

and Red Rock River through the Red 

Rock Lakes and into the upper drainage, 

and then returned downstream after 

spawning. The construction of a water 

control structure (sill) at the outlet of 

Lower Red Rock Lake in 1930 (and 

reconstructed in 1957 (USFWS 2009, p. 

74)) created an upstream migration 

barrier that blocked these migrations 

(Unthank 1989, p. 10; Gillin 2001, p. 4- 

4). This structure, along with mainstem 

dams at Lima and Clark Canyon, 

extirpated spawning runs of Arctic 

grayling that historically migrated 

through the Beaverhead and Red Rock 

Rivers (see Figure 2; USFWS 2009, p. 

72). All of these structures preclude 

upstream movement by fishes, and 

continue to prohibit immigration of 

Arctic grayling from the Big Hole River 

(see Figure 2). Because recovery of 

Arctic grayling will necessitate 

expansion into unoccupied habitat, and 

the Big Hole River includes some of the 

best remaining habitat for the species, 

these dams constitute a threat to Arctic 

grayling now and in the foreseeable 

future, which is 30 to 50 years based on 

the duration of existing FERC licenses 

in the upper basin. 

In Mussigbrod Lake, Arctic grayling 

occasionally pass downstream over a 

diversion structure at the lake outlet, 

and become trapped in a pool that is 

isolated because of stream dewatering 

(Magee and Olsen 2010, pers. comm.). 

However, the potential for mortality in 

these fish is partially mitigated by 

MFWP, which periodically captures 

Arctic grayling in this pool and returns 

them to the lake. 

In the Red Rock Lakes system, the 

presence of fish passage barriers 

represents a past and present threat. The 

magnitude of the threat may be reduced 

in the next 15 years as a result of 

implementation of the Red Rock Lakes 

NWR Comprehensive Conservation Plan 

(CCP) (USFWS 2009, entire — see 

Factor D discussion below), but we 

conclude that not all barriers that 

potentially affect the population will 

addressed during this time (e.g., Lower 

Red Rock Lake Water Control Structure) 

(USFWS 2009, p. 43). Thus, fish passage 

barriers will remain a threat to the Red 

Rock Lakes grayling in the foreseeable 

future. 

In the Big Hole River, fish passage 

barriers represent a past and present 

threat. The magnitude of the threat in 

the Big Hole River should decrease 

appreciably during the next 10 to 20 

years, which represents the foreseeable 

future in terms of the potential for the 

Big Hole Grayling CCAA to address the 

threat. Additional projects, such as the 

replacement of the Divide Dam, also 

should reduce the threat in the 

foreseeable future. 

Dewatering From Irrigation and 

Consequent Increased Water 

Temperatures 

Demand for irrigation water in the 

semi-arid upper Missouri River basin 

has dewatered many rivers formerly or 

currently occupied by Arctic grayling. 

The primary effects of this dewatering 

are: 1) Increased water temperatures, 

and 2) reduced habitat capacity. In 

ectothermic species like salmonid 

fishes, water temperature sets basic 

constraints on species distribution and 

physiological performance, such as 

activity and growth (Coutant 1999, pp. 

32–52). Increased water temperatures 

can reduce the growth and survival of 

Arctic grayling (physiological stressor). 

Reduced habitat capacity can 

concentrate fishes and thereby increase 

competition and predation (ecological 

stressor). 

In the Big Hole River system, surfacewater (flood) irrigation has substantially 

altered the natural hydrologic function 

of the river and has led to acute and 

chronic stream dewatering (Shepard and 

Oswald 1989, p. 29; Byorth 1993, p. 14; 

1995, pp. 8–10; Magee et al. 2005, pp. 

13–15). Most of the Big Hole River 

mainstem exceeds water quality 

standards under the Clean Water Act 

(33. U.S.C. 1251 et seq.; see discussion 

under Factor D, below) because of high 

summer water temperatures (Flynn et 

al. 2008, p. 2). Stream water 

temperature is affected by flow volume, 

stream morphology, and riparian 

shading, along with other factors, but an 

inverse relationship between flow 

volume and water temperature is 

apparent in the Big Hole River (Flynn et 

al. 2008, pp. 18–19). Summer water 

temperatures exceeding 21 °C (70 °F) are 


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considered to be physiologically 

stressful for cold-water fish species, 

such as Arctic grayling (Hubert et al. 

1985, pp. 7, 9). Summer water 

temperatures consistently exceed 21 °C 

(70 °F) in the mainstem of Big Hole 

River (Magee and Lamothe 2003, pp. 

13–14; Magee et al. 2005, p. 15; Rens 

and Magee 2007, p. 11). Recently, 

summer water temperatures have 

consistently exceeded the upper 

incipient lethal temperature (UILT) for 

Arctic grayling (e.g., 25 °C or 77 °F) 

(Lohr et al. 1996) at a number of 

monitoring stations throughout the Big 

Hole River (Magee and Lamothe 2003, 

pp. 13–14; Magee et al. 2005, p. 15; Rens 

and Magee 2007, p. 11). The UILT is the 

temperature that is survivable 

indefinitely (for periods longer than 1 

week) by 50 percent of the ‘‘test 

population’’ in an experimental setting. 

Fish kills are a clear result of high water 

temperature and have been documented 

in the Big Hole River (Lohr et al. 1996, 

p. 934). Consequently, water 

temperatures that are high enough to 

cause mortality of fish in the Big Hole 

River represent a clear threat to Arctic 

grayling because of the potential to 

directly and quickly reduce the size of 

the population. 

Water temperatures below that which 

can lead to instant mortality also can 

affect individual fish. At water 

temperatures between 21 °C (70 °F) and 

25 °C (77 °F), Arctic grayling can 

survive but experience chronic stress 

that can impair feeding and growth, 

reduce physiological performance, and 

ultimately reduce survival and 

reproduction. As described above, the 

Big Hole River periodically experiences 

summer water temperatures high 

enough to cause morality and chronic 

stress to Arctic grayling. Increased water 

temperature also appears to be a threat 

to Arctic grayling in the Madison River 

and Red Rock watershed. Mean and 

maximum summer water temperatures 

can exceed 21 °C (70 °F) in the Madison 

River below Ennis Reservoir (U.S. 

Geological Survey (USGS) 2010), and 

have exceeded 22 °C (72 °F) in the 

reservoir, and 24 °C (75 °F) in the 

reservoir inlet (Clancey and Lohrenz 

2005, p. 34). Similar or higher 

temperatures have been noted at these 

same locations in recent years (Clancey 

2002, p. 17; 2003, p. 25; 2004, pp. 29– 

30). Surface water temperatures in 

Upper Red Rock Lake as high as 24 °C 

(75 °F) have been recorded (Gillin 2001, 

p. 4-6), and presence of Arctic grayling 

in the lower 100 m (328 ft) of East 

Shambow Creek in 1994 was attributed 

to fish seeking refuge from high water 

temperatures in the lake (Mogen 1996, 

p. 44). Mean summer water 

temperatures in Red Rock Creek can 

occasionally exceed 20°C or 68°F during 

drought conditions (Mogen 1996, pp. 

19, 45). Arctic grayling can survive but 

experience chronic stress that can 

impair feeding and growth, reduce 

physiological performance, and 

ultimately reduce survival and 

reproduction. 

Experimental data specifically linking 

hydrologic alteration and dewatering to 

individual and population-level effects 

for Arctic grayling is generally lacking 

(Kaya 1992, p. 54), but we can infer 

effects from observations that the 

abundance and distribution of Arctic 

grayling has declined concurrent with 

reduced streamflows (MFWP et al. 2006, 

pp. 39–40) and increased water 

temperatures associated with low 

streamflows. 

In the Big Hole River system, earlyseason (April through May) irrigation 

withdrawals may dewater grayling 

spawning sites (Byorth 1993, p. 22), 

preventing spawning or causing egg 

mortality; can prevent juvenile grayling 

from accessing cover in the vegetation 

along the shoreline; and may reduce 

connectivity between necessary 

spawning, rearing, and refuge habitats. 

Severe dewatering reduces habitat 

volume and may concentrate fish, 

increasing the probability of 

competition and predation among and 

between species. Nonnative trout 

species presently dominate the 

salmonid community in the Big Hole 

River, so dewatering would tend to 

concentrate Arctic grayling in habitats 

where interactions with these nonnative 

trout would be likely. 

Especially in the Big Hole River, 

dewatering from irrigation represents a 

past and present threat to Arctic 

grayling. Thermal loading has 

apparently been a more frequent 

occurrence in the Big Hole River than in 

other locations containing native Arctic 

grayling (e.g., Red Rock Creek and 

Madison River–Ennis Reservoir). 

Implementation of the Big Hole Grayling 

CCAA during the next 20 years, which 

requires conservation measures to 

increase stream flows and restore 

riparian habitats (MFWP 2006, pp. 22– 

48), should significantly reduce the 

threat of thermal loading for Big Hole 

River grayling in the foreseeable future. 

While we expect agricultural and 

ranching-related use of water to 

continue, we expect that the threat will 

be reduced, but not eliminated, in the 

foreseeable future in the Big Hole River 

as a consequence of the CCAA. The 

ability of the Big Hole Grayling CCAA 

to augment streamflows should be 

substantial, as non-Federal landowners 

who control approximately 50 to 70 

percent of the points of irrigation 

diversion in the upper Big Hole River 

are enrolled in the CCAA (Roberts and 

Lamothe 2010, pers. comm.). However, 

the Big Hole River constitutes one 

population in the DPS and high water 

temperatures are likely to continue to 

affect grayling in the Madison River and 

Red Rock Lakes. Thus, stream 

dewatering and high water temperatures 

are expected to remain a threat to the 

DPS in the foreseeable future. 

Entrainment 

Entrainment can permanently remove 

individuals from the natural population 

and strand them in a habitat that lacks 

the required characteristics for 

reproduction and survival. Irrigation 

ditches may dry completely when 

irrigation headgates are closed, resulting 

in mortality of entrained grayling. 

Entrainment of individual Arctic 

grayling in irrigation ditches occurs in 

the Big Hole River (Skarr 1989, p. 19; 

Streu 1990, pp. 24–25; MFWP et al. 

2006, p. 49; Lamothe 2008, p. 22). Over 

1,000 unscreened diversion structures 

occur in the upper Big Hole River 

watershed, and more than 300 of these 

are located in or near occupied grayling 

habitat (MFWP et al. 2006, pp. 48–49). 

The magnitude of entrainment at 

unscreened diversions can depend on a 

variety of physical and biological 

factors, including the volume of water 

diverted (Kennedy 2009, p. iv, 36–38; 

but see Post et al. 2007, p. 885), speciesspecific differences in the timing of 

migratory behavior relative to when 

water is being diverted (Carlson and 

Rahel 2007, pp. 1340–1341), and 

differences in vulnerability among body 

size or life-stage (Gale 2005, pp. 30–47; 

Post et al. 2006, p. 975; Carlson and 

Rahel 2007 pp. 1340–1341). Studies of 

other salmonid species in a river basin 

in southwestern Wyoming determined 

that ditches typically entrain a small 

proportion (less than 4 percent) of the 

total estimated trout in the basin 

(Carlson and Rahel 2007, p. 1335) and 

that this represented a very small 

percentage of the total mortality for 

those populations (Post et al. 2006, pp. 

875, 884; Carlson and Rahel 2007, pp. 

1335, 1339). Whether or not this amount 

of mortality can cause population 

instability is unclear (Post et al. 2006, p. 

886; Carlson and Rahel 2007, pp. 1340– 

1341). However, in some cases, even 

small vital rate changes in a trout 

population can theoretically cause 

population declines (Hilderbrand 2003, 

pp. 260–261). 

The overall magnitude and 

population-level effect of entrainment 

on Arctic grayling in the Big Hole River 


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is unknown but possibly significant 

given the large number of unscreened 

surface-water diversions in the system 

and the large volumes of water diverted 

for irrigation. Given the low abundance 

of the species, even a small amount of 

entrainment may be biologically 

significant and is unlikely to be offset by 

compensatory effects (i.e., higher 

survival in Arctic grayling that are not 

entrained). 

Entrainment also may be a problem 

for Arctic grayling at some locations 

within the Red Rock Lakes system 

(Unthank 1989, p. 10; Gillin 2001, pp. 

2-4, 3-18, 3-25), particularly outside of 

the Red Rock Lakes NWR (Boltz 2010, 

pers. comm.). 

Entrainment has been a past threat to 

Arctic grayling in the Big Hole River 

and the Red Rock Lakes system. It 

remains a current threat as most, if not 

all, irrigation diversions located in 

occupied habitat do not have any 

devices to exclude fish (i.e., fish 

screens). Entrainment will remain a 

threat in the foreseeable future unless 

diversion structures are modified to 

exclude fish. The Big Hole Grayling 

CCAA has provisions to reduce 

entrainment at diversions operated by 

enrolled landowners (MFWP et al. 2006, 

pp. 50–52). Non-Federal landowners 

enrolled in the CCAA control 

approximately 50 to 70 percent of the 

points of irrigation diversion in the 

upper Big Hole River (Roberts and 

Lamothe 2010, pers. comm.), so the 

threat of entrainment in the Big Hole 

River should be significantly reduced in 

the foreseeable future. We consider the 

foreseeable future to represent 

approximately 20 years based on the 

duration of the Big Hole Grayling 

CCAA. Under the auspices of the Red 

Rock Lakes NWR CCP, a fish screen is 

planned to be installed on at least one 

diversion on the Red Rock Creek 

(USFWS 2009, p. 72), which is the 

primary spawning tributary for Arctic 

grayling in the Red Rock Lakes system. 

Overall, we anticipate it may take years 

to design and install fish screens on all 

the diversions that can entrain grayling 

in the Big Hole River and Red Rock 

Lakes systems; thus we conclude that 

entrainment remains a current threat 

that will continue to exist, but will 

decline in magnitude during the 

foreseeable future (next 10 to 20 years) 

because of implementation of the CCAA 

and CCP. 

Degradation of Riparian Habitat 

Riparian corridors are important for 

maintaining habitat for Arctic grayling 

in the upper Missouri River basin, and 

in general are critical for the ecological 

function of aquatic systems (Gregory et 

al. 1991, entire). These riparian zones 

are important for Arctic grayling 

because of their effect on water quality 

and role in creating and maintaining 

physical habitat features (pools) used by 

the species. 

Removal of willows and riparian 

clearing concurrent with livestock and 

water management along the Big Hole 

River has apparently accelerated in 

recent decades, and, in conjunction 

with streamside cattle grazing, has led 

to localized bank erosion, channel 

instability, and channel widening 

(Confluence Consulting et al. 2003, pp. 

24–26; Petersen and Lamothe 2006, pp. 

16–17; Bureau of Land Management 

(BLM) 2009a, pp. 14–21). Arctic 

grayling abundance in the upper Big 

Hole River is positively related to the 

presence of overhanging vegetation, 

primarily willows, which are associated 

with pool habitat (Lamothe and Magee 

2004b, pp. 21–22). Degradation of 

riparian habitat in the upper Big Hole 

River has led to a shift in channel form 

(from multiple threads to a single wide 

channel), increased erosion rates, 

reduced cover, increased water 

temperatures, and reduced recruitment 

of large wood into the active stream 

channel (Confluence Consulting et al. 

2003, pp. 24–26). All of these combine 

to reduce the suitability of the habitat 

for species like Arctic grayling, and 

likely reduce grayling growth, survival, 

and reproduction. 

Livestock grazing both within the Red 

Rock Lakes NWR and on adjacent 

private lands has negatively affected the 

condition of riparian habitats on 

tributaries to the Red Rock Lakes 

(Mogen 1996, pp. 75–77; Gillin 2001, 

pp. 3-12, 3-14). In general, degraded 

riparian habitat limits the creation and 

maintenance of aquatic habitats, 

especially pools, that are preferred 

habitats for adult Arctic grayling 

(Lamothe and Magee 2004b, pp. 21–22; 

Hughes 1992, entire). Loss of pools 

likely reduces growth and survival of 

adult grayling. Loss of riparian 

vegetation increases bank erosion, 

which can lead to siltation of spawning 

gravels, which may in turn harm 

grayling by reducing the extent of 

suitable spawning habitat and reducing 

survival of Arctic grayling embryos 

already present in the stream gravels. 

The condition of riparian habitats 

upstream from the Upper and Lower 

Red Rock Lakes may have improved 

during the 1990s (Mogen 1996, p. 77), 

and ongoing efforts to improve grazing 

management and restore riparian 

habitats are ongoing both inside the Red 

Rock Lakes NWR (USFWS 2009, pp. 67, 

75) and upstream (AGW 2010, p. 7; Korb 

2010, pers. comm.). However, the 

existing condition of riparian habitats 

continues to constitute a threat to Arctic 

grayling because the loss of pool habitat 

and the deposition of fine sediments 

may take some time to be reversed after 

the recovery of riparian vegetation. 

Much of the degradation of riparian 

habitats in the Big Hole River and Red 

Rock Lakes systems has occurred within 

the past 50 to 100 years, but the 

influence of these past actions continues 

to affect the structure and function of 

aquatic habitats in these systems. Thus, 

while the actual loss of riparian 

vegetation has presumably slowed 

during the past 10 years, the effect of 

reduced riparian vegetation continues to 

promote channel widening and 

sedimentation, and limits the creation 

and maintenance of pool habitats. Thus, 

degradation of riparian habitats is a 

current threat. Degradation of riparian 

habitats will remain a threat in the 

foreseeable future until riparian 

vegetation recovers naturally or through 

direct restoration, which may occur 

during the next 20 years in the Big Hole 

River and portions of the Red Rock 

Lakes system. Protection and direct 

restoration of riparian habitats in the Big 

Hole River is occurring on a fairly large 

scale under the provisions of the Big 

Hole Grayling CCAA (Lamothe et al. 

2007, pp. 13–26; Everett 2010, pp. 10– 

23), which should substantially reduce 

threats from riparian habitat degradation 

on private lands. Protection and 

restoration of riparian habitats 

implemented under the Red Rock Lakes 

NWR’s CCP (see discussion under 

Factor D, below) should reduce threats 

from riparian habitat degradation within 

the NWR’s boundary, but similar actions 

need to be taken on private lands 

adjacent to it (AGW 2010, p. 7; Korb 

2010, pers. comm.) to appreciably 

reduce these threats in the foreseeable 

future and to expand the distribution of 

the species into formerly occupied 

habitat within that drainage. 

Sedimentation 

Sedimentation has been proposed as a 

mechanism behind the decline of Arctic 

grayling and its habitat in the Red Rock 

Lakes (Unthank 1989, p. 10; Mogen 

1996, p. 76). Livestock grazing upstream 

has led to accelerated sediment 

transport in tributary streams, and 

deposition of silt in both stream and 

lakes has likely led to loss of fish habitat 

by filling in pools, covering spawning 

gravels, and reducing water depth in 

Odell and Red Rock Creeks, where 

Arctic grayling are still believed to 

spawn (MFWP 1981, p. 105; Mogen 

1996, pp. 73–76). 

Sedimentation in the Upper and 

Lower Red Rock Lakes is believed to 


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affect Arctic grayling by, in winter, 

reducing habitat volume (e.g., lakes 

freezing to the bottom) and promoting 

hypoxia (low oxygen), which generally 

concentrates fish in specific locations 

which have suitable depth, and thus 

increases the probability of competition 

and predation, and, in summer, causing 

thermal loading stress (see Dewatering 

From Irrigation and Consequent 

Increased Water Temperatures 

discussion, above). Depths in the Red 

Rock Lakes have decreased 

significantly, with a decline in 

maximum depth from 7.6 to 5.0 m (25 

to 16.4 ft) to less than 2 m (6.5 ft) noted 

in Upper Red Rock Lake over the past 

century (Mogen 1996, p. 76). Lower Red 

Rock Lake has a maximum depth of 

approximately 0.5 m (1.6 ft), and freezes 

within a few inches of the bottom or 

freezes solid (Unthank 1989, p. 10). 

Consequently, the Lower Red Rock Lake 

does not appear to provide suitable 

overwintering habitat for adfluvial 

Arctic grayling and may be devoid of 

grayling except for the few individuals 

that may migrate between Odell Creek 

and Upper Red Rock Lake (Mogen, 

1996, p. 47). 

Dissolved oxygen levels in Upper Red 

Rock Lake during winter 1994-1995 

dropped as low as 0.5 to 0.15 parts per 

million (ppm; Gangloff 1996, pp. 41–42, 

72), well below the critical minimum of 

1.3 to 1.7 ppm measured for adult Arctic 

grayling acclimated to water 

temperatures less than or equal to 8 °C 

(46 °F) (Feldmeth and Eriksen 1978, pp. 

2042–2043). Thus, lethally low oxygen 

levels can occur during winter in Upper 

Red Rock Lake, the primary 

overwintering area for adfluvial Arctic 

grayling in the system. Winter kill of 

invertebrates and fishes (e.g., suckers 

Catostomus spp.) has been recorded in 

Upper Red Rock Lake (Gangloff 1996, 

pp. 39–40). Gangloff (1996, pp. 71, 79) 

hypothesized that Arctic grayling in 

Upper Red Rock Lake exhibit behavioral 

mechanisms or physiological 

adaptations that permit them to survive 

otherwise lethally low oxygen levels. 

Oxygen conditions in the lake during 

winter are related to the effect of 

snowpack and ice cover on light 

penetration and the density of 

macrophytes (rooted aquatic plants) 

during the preceding growing season 

(Gangloff 1996, pp. 72-74). Arctic 

grayling under winter ice seek areas of 

higher oxygen concentration (oxygen 

refugia) within the lake or near inlet 

streams of Upper Red Rock Lake 

(Gangloff 1996, pp. 78-79). 

Consequently, we expect factors leading 

to reduced lake depth due to upstream 

erosion and sedimentation within the 

lake, or factors that promote 

eutrophication due to macrophyte 

growth, to lead to more frequent winter 

hypoxia (low dissolved oxygen 

concentrations detrimental to aquatic 

organsims) in Upper Red Rock Lake, 

which is the most important 

overwintering habitat for adfluvial 

Arctic grayling in the system. 

The effects of erosion and 

sedimentation on spawning gravels and 

reduction of habitat volume in Upper 

and Lower Red Rock Lakes are past and 

current threats. Improved land use may 

be reducing the rates of erosion in 

tributary streams (USFWS 2009, pp. 75– 

76; Korb 2010, pers. comm.). However, 

sedimentation of the lakes will likely 

remain a threat (because of reduced 

overwintering habitat, and high water 

temperatures in summer) in the 

foreseeable future unless some event 

mobilizes these sediments and 

transports them out of the lakes. 

Protection and restoration of riparian 

habitats implemented under the Red 

Rock Lakes NWR’s CCP (see discussion 

under Factor D, below) should reduce 

the magnitude of sedimentation within 

the NWR’s boundaries, but similar 

actions need to be taken on private 

lands adjacent to it (AGW 2010, p. 7; 

Korb 2010, pers. comm.) to appreciably 

reduce threats in the foreseeable future. 

Summary of Factor A 

Based on the best available 

information, we find that the historical 

range of the Missouri River DPS of 

Arctic grayling has been greatly 

reduced, and the remaining native 

populations continue to face significant 

threats to their habitat. Large-scale 

habitat fragmentation by dams was 

likely a significant historical factor 

causing the range-wide decline of the 

DPS. The most significant current 

threats to the DPS are from land and 

water use activities that have affected 

the structure and function of aquatic 

systems, namely stream dewatering 

from irrigation withdrawals, which 

reduces habitat volume and increases 

summer water temperatures; potential 

loss of individuals in irrigation ditches 

(entrainment); degraded riparian 

habitats promoting erosion, 

sedimentation, increased water 

temperatures, and loss of pool habitat; 

and migration barriers that restrict 

movement to and from spawning, 

feeding, and sheltering habitats. These 

are among the significant current threats 

to Arctic grayling populations in the Big 

Hole River, Madison River–Ennis 

Reservoir, and Red Rock Lakes system. 

The habitat-related threats to the Big 

Hole River population should be 

reduced in the foreseeable future by 

implementation of the Big Hole Grayling 

CCAA, a formalized conservation plan 

with 32 private landowners currently 

enrolled. The Big Hole Grayling CCAA 

is expected to reduce threats from 

dewatering, high water temperatures, 

barriers to fish passage, and entrainment 

in irrigation ditches that are associated 

with land and water use in the upper 

Big Hole River watershed during the 

foreseeable future (next 20 years based 

on the duration of the CCAA). NonFederal landowners enrolled in the Big 

Hole Grayling CCAA control or own 

approximately 50 to 70 percent of the 

points of irrigation diversion in the 

upper Big Hole River, so these 

landowners should have the ability to 

reduce habitat-related threats to Arctic 

grayling in the Big Hole River by a 

corresponding amount. However, the 

present or threatened destruction, 

modification, or curtailment of habitat 

remains a threat to the DPS overall. This 

factor is expected to continue to be a 

threat to the species in the foreseeable 

future because it is not comprehensively 

addressed for other populations, 

especially those in the Madison River 

and Red Rock Lakes systems where 

ongoing habitat-related threats 

(described above) may be making 

unoccupied habitat unsuitable for Arctic 

grayling, and may thus limit the 

recovery potential of the DPS. 

B. Overutilization for Commercial, 

Recreational, Scientific, or Educational 

Purposes 

Arctic grayling of the upper Missouri 

River are handled for recreational 

angling; and for scientific, population 

monitoring, and restoration purposes. 

Recreational Angling 

Arctic grayling are highly susceptible 

to capture by angling (ASRD 2005, pp. 

19–20), and intense angling pressure 

can reduce densities and influence the 

demography of exploited populations 

(Northcote 1995, pp. 171–172). 

Overfishing likely contributed to the 

rangewide decline of the DPS in the 

upper Missouri River system (Vincent 

1962, pp. 49–52, 55; Kaya 1992, pp. 54– 

55). In 1994, concern over the effects of 

angling on fluvial Arctic grayling led the 

State of Montana to implement catchand-release regulations for Arctic 

grayling captured in streams and rivers 

within its native range, and those 

regulations remain in effect (MFWP 

2010, p. 52). Catch-and-release 

regulations for Arctic grayling in the Big 

Hole River have been in effect since 

1988 (Byorth 1993, p. 8). Catch-andrelease regulations also are in effect for 

Ennis Reservoir on the Madison River 

(MFWP 2010, p. 61). Angling is not 


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permitted in either of the Red Rock 

Lakes to protect breeding waterfowl and 

trumpeter swans (Cygnus buccinator) 

(USFWS 2009, p. 147), and catch-andrelease regulations remain in effect for 

any Arctic grayling captured in streams 

(e.g., Odell Creek or Red Rock Creek) in 

the Red Rock Lakes system (MFWP 

2010, p. 56). 

In Miner and Mussigbrod Lakes, 

anglers can keep up to 5 Arctic grayling 

per day and have up to 10 in possession, 

in accordance with standard daily and 

possession limits for that angling 

management district (MFWP 2010, p. 

52). The current abundance of Arctic 

grayling in Mussigbrod Lake (see Table 

4 above) suggests that present angling 

exploitation rates are not a threat to that 

population. Miner Lakes grayling are 

less abundant compared to Mussigbrod 

Lake, but we are not sure whether 

angling exploitation constitutes a threat 

to Miner Lakes grayling. 

Repeated catch-and-release angling 

may harm individual fish, causing 

physiological stress and injury (i.e., 

hooking wounds). Catch-and-release 

angling also can result in mortality at a 

rate dependent on hooking location, 

hooking duration, fish size, water 

quality, and water temperature 

(Faragher et al. 2004, entire; 

Bartholomew and Bohnsack 2005, p. 

140). Repeated hooking (up to five 

times) of Arctic grayling in Alaska did 

not result in significant additional 

mortality (rates 0 to 1.4 percent; Clark 

1991, pp. 1, 25–26). In Michigan, 

hooking mortality of Arctic grayling in 

lakes averaged 1.7 percent per capture 

event based on 355 individuals captured 

with artificial flies and lures (Nuhfer 

1992, pp. 11, 29). Higher mortality rates 

(5 percent) have been reported for Arctic 

grayling populations in the Great Slave 

Lake area, Canada (Falk and Gillman 

1975, cited in Casselman 2005, p. 23). 

Comparatively high catch rates for 

Arctic grayling have been observed in 

the Big Hole River, Montana (Byorth 

1993, pp. 26–27, 36), and average 

hooking wound rates ranged from 15 to 

30 percent among study sections 

(Byorth 1993, p. 28). However, overall 

hooking mortality from single capture 

events was low (1.4 percent), which led 

Byorth to conclude that the Big Hole 

River population was not limited by 

angling (Byorth 1994b, entire). 

Compared to the average catch-andrelease mortality rates of 4.2 to 4.5 

percent in salmonids as reported by 

Schill and Scarpella (1997, p. 873), and 

the mean and median catch-and-release 

mortality rates of 18 percent and 11 

percent from a meta-analysis of 274 

studies (Bartholomew and Bohnsack 

2005, pp. 136–137), the catch-andrelease mortality rates for Arctic 

grayling are comparatively low (Clark 

1991, pp. 1, 25–26; Nuhfer 1992, pp. 11, 

29; Byorth 1994b, entire). We are 

uncertain whether these lower observed 

rates reflect an innate resistance to 

effects of catch-and-release angling in 

Arctic grayling or whether they reflect 

differences among particular 

populations or study designs used to 

estimate mortality. Even if catch-andrelease angling mortality is low (e.g., 1.4 

percent as reported in Byorth 1994b, 

entire), the high catchability of Arctic 

grayling (ASRD 2005, pp. 19–20) raises 

some concern about the cumulative 

mortality of repeated catch-and-release 

captures. For example, based on the 

Arctic grayling catch rates and angler 

pressure reported by Byorth (1993, pp. 

25–26) and the population estimate for 

the Big Hole River reported in Byorth 

(1994a, p. ii), a simple calculation 

suggests that age 1 and older grayling 

susceptible to recreational angling may 

be captured and released 3 to 6 times 

per year. 

The MFWP closes recreational angling 

in specific reaches of the Big Hole River 

when environmental conditions are 

considered stressful. Specific 

streamflow and temperature thresholds 

initiate mandatory closure of the fishery 

(Big Hole Watershed Committee 1997, 

entire). Such closures have been 

implemented in recent years. For 

example, the upper segment of the Big 

Hole River between Rock Creek Road to 

the confluence of the North Fork Big 

Hole River has been closed to angling at 

various times during 2004 (Magee et al. 

2005, p. 7), 2005 (Magee et al. 2006, p. 

20), and 2006 (Rens and Magee 2007, p. 

8). 

In conclusion, angling harvest may 

have significantly reduced the 

abundance and distribution of the upper 

Missouri River DPS of Arctic grayling 

during the past 50 to 100 years, but 

current catch-and-release fishing 

regulations (or angling closures) in most 

waters occupied by extant populations 

have likely ameliorated the past threat 

of overharvest. Although we have some 

concerns about the potential for 

cumulative mortality caused by 

repeated catch-and-release of individual 

Arctic grayling in the Big Hole River, we 

have no strong evidence indicating that 

repeated capture of Arctic grayling 

under catch-and-release regulations is 

currently limiting that population or the 

DPS. Moreover, fishing is restricted in 

the Big Hole River, an important 

recreational fishing destination in 

southwestern Montana, when 

streamflow and temperature conditions 

are likely to increase stress to captured 

grayling. Anglers can still capture and 

keep Arctic grayling in Miner and 

Mussigbrod Lakes in accordance with 

State fishing regulations, but we have no 

evidence that current levels of angling 

are affecting these populations. We thus 

have no evidence that recreational 

angling represents a current threat to the 

DPS. If we assume that future fishing 

regulations would be at least as 

conservative as current regulations, and 

that the current levels of angling 

pressure will continue, then recreational 

angling does not represent a threat in 

the foreseeable future. 

Monitoring and Scientific Study 

The MFWP consistently monitors the 

Arctic grayling population in the Big 

Hole River and its tributaries, and to a 

lesser extent those populations in the 

Madison River and Red Rock Lakes 

system (Rens and Magee 20007, entire). 

Electrofishing (use of electrical current 

to temporarily and non-lethally 

immobilize a fish for capture) is a 

primary sampling method to monitor 

Arctic grayling in the Big Hole River, 

Madison River, and Red Rock Lakes 

(Rens and Magee 2007, pp. 13, 17, 20). 

A number of studies have investigated 

the effects of electrofishing on various 

life stages of Arctic grayling. Dwyer and 

White (1997, p. 174) found that 

electrofishing reduced the growth of 

juvenile Arctic grayling and concluded 

that long-term, sublethal effects of 

electrofishing were possible. Hughes 

(1998, pp. 1072, 1074–1075) found 

evidence that electrofishing and tagging 

affected the growth rate and movement 

behavior of Arctic grayling in the Chena 

River, Alaska. Roach (1999, p. 923) 

studied the effects of electrofishing on 

fertilized Arctic grayling eggs and found 

that while electrofishing could result in 

egg mortality, the population-level 

effects of such mortality were not likely 

to be significant. Lamothe and Magee 

(2003, pp. 16, 18–19) noted mortality of 

Arctic grayling in the Big Hole River 

during a radio-telemetry study, and 

concluded that handling stress or 

predation were possible causes of 

mortality. Population monitoring 

activities in the Big Hole River are 

curtailed when environmental 

conditions become unsuitable (Big Hole 

Watershed Committee 1997, entire), and 

recent monitoring reports (Magee and 

Lamothe 2004, entire; Magee et al. 2005, 

entire; Rens and Magee 2007, entire) 

provide no evidence that electrofishing 

is harming the Arctic grayling 

population in the Big Hole River. 

A study in the Big Hole River is 

investigating the availability and use of 

coldwater thermal refugia for Arctic 

grayling and other resident fishes 

(Vatland and Gressewell 2009, entire). 


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The study uses fish tagged with passive 

integrated transponder (PIT) tag 

technology to record movement past 

receiving antennas. The PIT tags are 

small (23 mm or less than 1 in. long) 

and implanted into the body cavity of 

the fish during a quick surgical 

procedure. During 2007–2008, a total of 

81 Arctic grayling from the Big Hole 

River and its tributaries were implanted 

with these PIT tags (Vatland and 

Gressewell 2009, p. 12). A short-term 

study on the potential effects of PIT tag 

implantation on Arctic grayling found 

100 percent retention of tags and 100 

percent survival of tagged individuals 

during a 4–day trial (Montana State 

University 2008, p. 7). Based on the 

results of the controlled trials, we have 

no evidence to indicate that PIT tagging 

the wild Arctic grayling in the Big Hole 

River constitutes a significant threat to 

the population. 

Traps, electrofishing, and radio 

telemetry have been used to monitor 

and study Arctic graying in the Red 

Rock Lakes system (Gangloff 1996, pp. 

13–14; Mogen 1996, pp. 10–13, 15; 

Kaeding and Boltz 1999, p. 4; Rens and 

Magee 2007, p. 17); however, there is no 

data to indicate these monitoring 

activities reduce the growth and 

survival of individual Arctic grayling or 

otherwise constitute a current or future 

threat to the population. 

The Arctic grayling population in the 

Madison River–Ennis Reservoir is not 

monitored as intensively as the Big Hole 

River population (Rens and Magee 2007, 

pp. 20–21). When electrofishing surveys 

targeting Arctic grayling in the Madison 

River do occur, they are conducted 

during the spawning run for that 

population (Clancey 1996, p. 6). Capture 

and handling during spawning 

migrations or during actual spawning 

could affect the reproductive success of 

individual Arctic grayling. However, 

under recent monitoring frequencies, 

any population-level effect of these 

activities is likely negligible, and we 

have no data to indicate these 

monitoring activities reduce the growth 

and survival of individual Arctic 

grayling or otherwise constitute a 

current or future threat to the Madison 

River population. 

The Miner Lakes and Mussigbrod 

Lake populations of Arctic grayling are 

infrequently monitored (Olsen 2010, 

pers. comm.). Since monitoring of these 

populations has been minimal, we do 

not believe that monitoring or scientific 

study constitutes a current or 

foreseeable threat to these particular 

populations. 

The intensity of monitoring and 

scientific investigation varies among the 

different populations in the DPS, but we 

have no evidence suggesting that 

monitoring or scientific study has 

influenced the decline of Arctic grayling 

in the Missouri River basin. We also 

have no evidence indicating these 

activities constitute a current threat to 

the DPS that would result in 

measurable, population-level effects. We 

expect similar levels of population 

monitoring and scientific study in the 

future, and we have no basis to 

conclude that these activities represent 

a threat in the foreseeable future. 

Reintroduction Efforts 

Attempts to restore or re-establish 

native populations of both fluvial and 

adfluvial Arctic grayling may result in 

the mortality of embryos and young fish. 

The MFWP attempted to restore fluvial 

Arctic graying to historic waters in the 

upper Missouri River using a 

combination of stocking and embryo 

incubating devices (remote site 

incubators) placed in target streams 

(Rens and Magee 2007, pp. 24–38). 

Currently, gametes (eggs and sperm) 

used to re-establish the fluvial ecotype 

come from captive brood reserves of Big 

Hole River grayling maintained in 

Axolotl and Green Hollow II Lakes 

(Rens and Magee 2007, pp. 22–24). 

Removal of gametes from the wild Big 

Hole River population was necessary to 

establish this brood reserve (Leary 1991, 

entire). The previous removal of 

gametes for conservation purposes may 

have reduced temporarily the 

abundance of the wild population if the 

population was unable to compensate 

for this effective mortality by increased 

survival of remaining individuals. 

However, the establishment of a brood 

reserve provides a conservation benefit 

from the standpoint that gametes from 

the reserve can be harvested to use for 

translocation efforts to benefit the 

species. Unfortunately, these 

translocations have not yet resulted in 

establishment of any fluvial 

populations. Ultimately, we do not have 

any data to indicate that past gamete 

collection from the Big Hole River 

population harmed the wild population. 

Consequently, we have no basis to 

conclude that gamete collection from 

the wild Big Hole River Arctic grayling 

population constitutes a current or 

future threat to the population. 

Efforts to re-establish native, 

genetically pure populations of 

adfluvial Arctic grayling in the Red 

Rock Lakes system and to maintain a 

brood reserve for that population have 

resulted in the direct collection of eggs 

from Arctic grayling spawning runs in 

Red Rock Creek. During 2000–2002, an 

estimated 315,000 Arctic grayling eggs 

were collected from females captured in 

Red Rock Creek (Boltz and Kaeding 

2002, pp. v, 8). The Service placed over 

180,000 of these eggs in remote site 

incubators in streams within the Red 

Rock Lakes NWR that historically 

supported Arctic grayling spawning 

runs (Boltz and Kaeding 2002, pp. v, 

10). Despite preliminary observations of 

grayling spawning in historically 

occupied waters within the Red Rock 

Lakes NWR following the use of remote 

site incubators (Kaeding and Boltz 2004, 

pp. 1036), spawning runs at these 

locations have apparently not become 

established (Boltz 2006, pers. comm.). 

Attempts to establish a brood reserve of 

adfluvial Arctic grayling within the 

NWR’s boundaries (MacDonald Pond) 

were not successful (Boltz and Kaeding 

2002, pp. 21–22). Red Rock Lakes NWR 

plans to re-establish Arctic grayling in 

Elk Springs and Picnic Creeks and 

establish a brood stock in Widgeon 

Pond as part of its CCP (USFWS 2009, 

pp. 72, 75). The MFWP and the Service 

are currently collaborating on an effort 

to re-establish an Arctic grayling 

spawning run in Elk Springs Creek and 

to establish a genetically pure brood 

reserve of Red Rock Lakes grayling in 

Elk Lake as no such population exists 

for use in conservation and recovery 

(Jordan 2010, pers. comm.). These 

actions will require the collection of 

gametes (approximately 360,000 eggs) 

from Arctic grayling captured in Red 

Rock Creek (Jordan 2010, pers. comm.). 

Approximately 10 percent of these eggs 

will be returned to Red Rock Creek and 

incubated in that stream (using a remote 

site incubation method that results in 

high survivorship of embryos) (Kaeding 

and Boltz 2004, entire) to mitigate for 

collection of gametes from the wild 

spawning population (Jordan 2010, pers. 

comm.). We presume these ongoing 

actions may necessitate the collection of 

gametes from wild Arctic grayling in 

Red Rock Creek, so the potential effect 

of such collections on the extant wild 

population should be evaluated and 

mitigation for the use of these gametes 

(e.g., using remote site incubators at the 

collection source or another method) 

should continue. 

Overall, we have no evidence to 

indicate that collection of gametes from 

the wild populations in the Big Hole 

River and Red Rock Lakes systems have 

contributed to population-level declines 

in those populations, or that the 

previous collections represent 

overexploitation. Future plans to collect 

gametes from Arctic grayling in the Big 

Hole River and Red Rock Lakes should 

be carefully evaluated in light of the 

status of those populations at the 

anticipated time of the collections. We 


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encourage the agencies involved to 

coordinate their efforts and develop a 

strategy for broodstock development 

and recovery efforts that minimizes any 

potential impacts to wild native 

populations. However, at present, we do 

not have any data indicating collection 

of gametes for conservation purposes 

represents a current threat to the Big 

Hole River and Red Rock Lakes 

populations. We have no evidence to 

indicate that gamete collection will 

increase in the future, so we have no 

basis to conclude that this represents a 

threat in the foreseeable future. 

Summary of Factor B 

Based on the information available at 

this time, we conclude that 

overexploitation by angling may have 

contributed to the historical decline of 

the upper Missouri River DPS of Arctic 

grayling, but we have no evidence to 

indicate that current levels of 

recreational angling, population 

monitoring, scientific study, or 

conservation actions constitute 

overexploitation; therefore, we do not 

consider them a threat. We expect 

similar levels of these activities to 

continue in the future, and we do not 

believe they represent a threat in the 

foreseeable future. 

C. Disease or Predation 

Disease 

Arctic grayling are resistant to 

whirling disease, which is responsible 

for population-level declines of other 

stream salmonids (Hedrick et al. 1999, 

pp. 330, 333). However, Arctic grayling 

are susceptible to bacterial kidney 

disease (BKD). Some wild populations 

in pristine habitats test positive for BKD 

(Meyers et al. 1993, pp. 186–187), but 

clinical effects of the disease are more 

likely to be evident in captive 

populations (Meyers et al. 1993, entire; 

Peterson 1997, entire). To preclude 

transmission of BKD between grayling 

during brood reserve, hatchery, and 

wild grayling translocation efforts, 

MFWP tests kidney tissue and ovarian 

fluid for the causative agent for BKD as 

well as other pathogens in brood 

populations (Rens and Magee 2007, pp. 

22–24). 

Information on the prevalence of the 

BKD or other diseases in native Arctic 

grayling populations in Montana is 

generally lacking. One reason is that 

some disease assays are invasive or 

require the sacrifice of individual fish 

(e.g., removal of kidney tissue to test for 

BKD pathogen.) Therefore, such testing 

is typically avoided in native 

populations of Missouri River Arctic 

grayling that are low in abundance. 

Arctic grayling in captive brood reserves 

(e.g., Axolotl Lake, Green Hollow Lake) 

and introduced populations (e.g., 

Sunnyslope Canal, Rogers Lake) have all 

tested negative for infectious 

hematopoietic necrosis virus (IHNV), 

infectious pancreatic necrosis virus 

(IPNV), Myxobolus cerebralis (the 

pathogen that causes whirling disease), 

Renibacterium salmoninarum (the 

pathogen that causes BKD), and 

Aeromonas salmonicida (the pathogen 

that causes furunculosis) (USFWS 

2010a). Consequently, we have no 

evidence at this time that disease 

threatens native Arctic grayling of the 

upper Missouri River. We have no basis 

to conclude that disease will become a 

future threat, so we conclude that 

disease does not constitute a threat in 

the foreseeable future. 

Predation By and Competition With 

Nonnative Trout 

Brook trout (Salvelinus fontinalis), 

brown trout (Salmo trutta), and rainbow 

trout have been introduced across the 

United States to provide recreational 

fishing opportunities, and are now 

widely distributed and abundant in the 

western United States, including the 

upper Missouri River system (Schade 

and Bonar 2005, p. 1386). One or more 

of these nonnative trout species cooccur with every native Arctic grayling 

population in the basin. Ecological 

interactions (predation and competition) 

with the brook trout, brown trout, and 

rainbow trout are among the longstanding hypotheses to explain decline 

of Arctic grayling in the upper Missouri 

River system and the extirpation of 

populations from specific waters 

(Nelson 1954, p. 327; Vincent 1962, pp. 

81–96; Kaya 1992, pp. 55–56). 

The potential for interspecific 

interactions should be greatest among 

species with similar life histories and 

ecologies that did not co-evolve (Fausch 

and White 1986, p. 364). Arctic grayling 

in the Missouri River basin have similar 

ecologies to brook trout, rainbow trout, 

and brown trout, yet they do not share 

a recent evolutionary history. The 

evidence for predation and competition 

by nonnative trout on Arctic grayling in 

the upper Missouri River basin is largely 

circumstantial, and inferred from the 

reduced abundance and distribution of 

Arctic grayling following encroachment 

by nonnative trout (Kaya 1990, pp. 52– 

54; Kaya 1992, p. 56; Magee and Byorth 

1995, p. 54), as well as the difficulty in 

establishing Arctic grayling populations 

in waters already occupied by nonnative 

trout, especially brown trout (Kaya 

2000, pp. 14–15). Presumably, 

competition with ecologically-similar 

species for food, shelter, and spawning 

locations can lead to reduced growth, 

reproduction, and survival of Arctic 

grayling (i.e., where they are 

outcompeted by nonnative trout). The 

strength of competition is very difficult 

to measure in wild trout populations 

(Fausch 1988, pp. 2238, 2243; 1998, pp. 

220, 227). Few studies have evaluated 

competition between Arctic grayling 

and these nonnative species. Brook trout 

do not appear to negatively affect 

habitat use or growth of juvenile, 

hatchery-reared Arctic grayling (Byorth 

and Magee 1998, p. 921), but further 

studies are necessary to determine 

whether competition or predation occur 

at other life stages or with brown or 

rainbow trout (Byorth and Magee 1998, 

p. 929). 

Predation represents direct mortality 

that can limit populations, and YOY 

Arctic grayling may be particularly 

susceptible to predation by other fishes 

because they are smaller and weaker 

swimmers than trout fry (Kaya 1990, pp. 

52–53). 

The incidence of competition and 

predation between nonnative trout and 

Arctic grayling likely depends on 

environmental context (e.g., habitat type 

and quality, environmental conditions 

such as temperature, and so forth). 

Nonetheless, it is widely accepted that 

biotic interactions with nonnative 

species are to some extent responsible 

for the decline of many native fishes in 

the western United States (Dunham et 

al. 2002, pp. 373–374 and references 

therein; Fausch et al. 2006, pp. 9–11 and 

references therein). 

In the Big Hole River, brook trout, 

rainbow trout, and brown trout have 

been established for some time (Kaya 

1992, pp. 50–51) and are much more 

abundant than Arctic grayling (Rens and 

Magee 2007, p. 42). In general, brook 

trout is the most abundant nonnative 

trout species in the Big Hole River 

upstream from Wisdom, Montana (Rens 

and Magee 2007, pp. 7, 42; Lamothe et 

al. 2007, pp. 35–38), whereas rainbow 

trout and brown trout are comparatively 

more abundant in the reaches 

immediately above and downstream 

from the Divide Dam (Kaya 1992, p. 56; 

Oswald 2005b, pp. 22–29; Lamothe et 

al. 2007, pp. 35–38; Rens and Magee 

2007, p. 10). Rainbow trout are 

apparently more abundant than brown 

trout above the Divide Dam (Olsen 2010, 

pers. comm.), but brown trout are more 

abundant than rainbow trout below the 

dam (Oswald 2005b, pp. 22–33). Recent 

observations of increased brown trout 

abundance and distribution in the upper 

Big Hole River indicate that the species 

may be encroaching further upstream 

(AGW 2008, p. 1). Overall, at least one 

nonnative species occurs in the 


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mainstem Big Hole River and tributary 

locations where Arctic grayling are 

present (Lamothe et al. 2007, p. 37; Rens 

and Magee 2007, p. 42). The Big Hole 

Grayling CCAA recognizes that the 

potential for competition with and 

predation by nonnative trout may limit 

the effectiveness of its conservation 

actions (MFWP et al. 2006, pp. 54–55). 

The MFWP is the lead agency 

implementing the Big Hole Grayling 

CCAA under an agreement with the 

Service, and MFWP establishes fishing 

regulations for most waters in Montana. 

Different regulations may apply on 

NWR lands administered by the Service. 

The MFWP has agreed to continue 

catch-and-release regulations for Arctic 

grayling in the Big Hole River, to 

increase daily possession limits for 

nonnative brook trout (MFWP et al. 

2006, p. 55; MFWP 2010, p. 52), and to 

consider whether additional 

management actions are necessary to 

address threats from nonnative trout 

based on recommendations of a 

technical committee of the AGW 

(MFWP et al. 2006, p. 55). However, we 

are not aware of data that shows angling 

regulations currently, or are expected to, 

reduce threats from brook trout. We also 

are not aware of any evaluations 

provided by the technical committee or 

of any additional management actions 

taken by MFWP to address potential 

threats from nonnative trout. Nonnative 

trout are widely distributed and 

abundant in the Big Hole River, and 

eradication may be impossible. The Big 

Hole Grayling CCAA focuses primarily 

on habitat-related threats (not nonnative 

trout), so we presume that nonnative 

trout will remain a threat to Arctic 

grayling for the foreseeable future. 

Arctic grayling in Miner and 

Mussigbrod Lakes co-occur with one or 

more species of nonnative trout, but we 

have no quantitative information on the 

relative abundance of the introduced 

species. Brook trout and rainbow trout 

are both characterized as ‘‘common’’ in 

lower Miner Lakes (MFISH 2010), and 

brook trout in Mussigbrod Lake are 

similarly categorized as ‘‘common’’ 

(MFISH 2010). Brook trout have been 

present in the Big Hole River for at least 

60 years (Liknes 1981, p. 34). The date 

when brook trout were introduced into 

Miner and Mussibrod Lakes is unknown 

(Liknes 1981, p. 33), but the cooccurrence of the brook trout with 

Arctic grayling in these habitats suggests 

that displacement of Arctic grayling by 

brook trout is not inevitable. 

In the Madison River in and near 

Ennis Reservoir, brown trout and 

rainbow trout are abundant and are the 

foundation of an important recreational 

fishery (e.g., Byorth and Shepard 1990, 

p. 1). Nonnative rainbow trout and 

brown trout substantially outnumber 

Arctic grayling in the Madison River 

near Ennis Reservoir (Clancey and 

Lohrenz 2005, pp. 26, 29–31; 2009, pp. 

91, 93). 

In the Red Rock Lakes system, brook 

trout and hybrid cutthroat trout 

(Yellowstone cutthroat trout 

(Oncorhynchus clarkii bouvieri) 

rainbow trout; Mogen 1996, p. 42) have 

well-established populations and 

dominate the abundance and biomass of 

the salmonid community (Katzman 

1998, pp. 2–3; Boltz 2010, pp. 2–3). 

Competition and predation risk for the 

Arctic grayling may be particularly 

acute in the shallow Upper Red Rock 

Lake when all fish species are forced to 

congregate in a few discrete deeper sites 

in response to environmental 

conditions, such as ice formation in 

winter (Boltz 2010, pers. comm.). 

Removal of nonnative trout from certain 

waters on the Red Rock Lakes NWR is 

part of the CCP (USFWS 2009, pp. 72, 

75), so the frequency of predation of and 

competition with Arctic grayling by 

these species may be reduced at a 

limited spatial scale during the 15–year 

timeframe of the CCP. 

Studies attempting to specifically 

measure the strength of competition 

with and magnitude of predation by 

nonnative trout on Arctic grayling in 

Montana have yielded mixed results. 

Only one study attempted to measure 

competition between brook trout and 

Arctic grayling (Byorth and Magee 1998, 

entire), and their study did not find 

strong evidence for presumed effects of 

competition, such as differences in 

microhabitat use or growth rate (Byorth 

and Magee 1998, p. 1998). However, the 

authors cautioned that further studies 

were needed to determine whether or 

not competition may be occurring 

between fish of different sizes or ages 

(other than those tested) or whether 

competition with or predation by 

rainbow trout or brown trout is 

occurring (Byorth and Magee, 1998, p. 

929). Measuring the strength of 

competition and determining the 

relevant mechanisms (e.g., competition 

for food vs. space) is difficult to measure 

in fish populations (Fausch 1998, pp. 

220, 227), so the lack of definitive 

evidence for the mechanisms of 

competition may simply be due to the 

inherent difficulties in measuring these 

effects and determining their influence 

on the population. Similarly, predation 

by brook trout on Arctic grayling eggs 

and fry has been observed in both the 

Big Hole River and Red Rock Lakes 

systems (Nelson 1954, entire; Streu 

1990, p. 17; Katzman 1998, pp. 35, 47, 

114), but such observations have not 

been definitively linked with a 

population decline of Arctic grayling. 

To our knowledge, no studies have 

investigated or attempted to measure 

predation by brown trout or rainbow 

trout on Arctic grayling in Montana. 

Experimental evidence 

notwithstanding, the decline of Arctic 

grayling concurrent with encroachment 

by nonnative trout, combined with the 

difficulty in establishing grayling 

populations where nonnatives trout are 

present (Kaya 1992, pp. 55–56, 61; Kaya 

2000, pp. 14–16), provides strong 

circumstantial evidence that a 

combination of predation and 

competition by nonnative trout has 

negatively affected Arctic grayling 

populations in the upper Missouri 

River. The lack of direct evidence for 

competition (e.g., with brook trout) or 

predation (e.g., by brown trout) most 

likely indicates that these mechanisms 

can be difficult to detect and measure in 

wild populations and that additional 

scientific investigation is needed. We 

recognize that displacement of Arctic 

grayling is not a certain outcome where 

the species comes into contact with 

brook trout (e.g., Big Hole River), but the 

circumstances that facilitate long-term 

co-existence vs. transitory co-existence 

are unknown. Ultimately, circumstantial 

evidence from Montana and the western 

United States suggests that the presence 

of nonnative trout species represents a 

substantial threat to native fishes 

including Arctic grayling. At least one 

species of nonnative trout is present in 

all waters occupied by native Arctic 

grayling populations in the upper 

Missouri River, so the threat is 

widespread and imminent, and we 

expect that nonnative trout will remain 

a part of the biological community. 

Thus, we expect that nonnative trout are 

a threat to Missouri River Arctic 

grayling in the foreseeable future. 

Predation by Birds and Mammals 

In general, the incidence and effect of 

predation by birds and mammals on 

Arctic grayling is not well understood 

because few detailed studies have been 

completed (Northcote 1995, p. 163). 

Black bear (Ursus americanus), mink 

(Neovison vison), and river otter (Lontra 

canadensis) are present in southwestern 

Montana, but direct evidence of 

predatory activity by these species is 

often lacking (Kruse 1959, p. 348). 

Osprey (Pandion halaietus) can capture 

Arctic grayling during the summer 

(Kruse 1959, p. 348). In the Big Hole 

River, Byorth and Magee (1998, p. 926) 

attributed the loss of Arctic grayling 

from artificial enclosures used in a 

competition experiment to predation by 

minks, belted kingfisher (Ceryl alcyon), 


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osprey, and great blue heron (Ardea 

herodia). In addition, American white 

pelican (Pelecanus erythrorhynchos) are 

seasonally present in the Big Hole River, 

and they also may feed on grayling. The 

aforementioned mammals and birds can 

be effective fish predators, but we have 

no data demonstrating any of these 

species historically or currently 

consume Arctic grayling at levels 

sufficient to exert a measureable, 

population-level impact on native 

Arctic grayling in the upper Missouri 

River system. We expect the current 

situation to continue, so we conclude 

that predation by birds and mammals 

does not constitute a substantial threat 

to Missouri River Arctic grayling in the 

foreseeable future. 

Summary of Factor C 

Based on the information available at 

this time, we conclude disease does not 

represent a past or current threat to the 

Missouri River DPS of Arctic grayling. 

We have no factual basis for concluding 

that disease may become a future threat, 

but anticipate that the likelihood of 

disease in native populations will 

depend on and interact with other 

factors (e.g., habitat condition, climate 

change) that may cumulatively stress 

individual fish and reduce their ability 

to withstand infection by diseasecausing pathogens. 

Circumstantial evidence indicates that 

ecological interactions with nonnative 

trout species have led to the 

displacement of Arctic grayling from 

portions of its historic range in the 

upper Missouri River basin. Nonnative 

trout species, such as brook trout, brown 

trout, and rainbow trout, remain widely 

distributed and abundant in habitats 

currently occupied by native Arctic 

grayling populations. Consequently, we 

determined that the presence of 

nonnative trout represents a substantial 

current and foreseeable threat to native 

Arctic grayling of the upper Missouri 

River. 

Little is known about the effect of 

predation on Arctic grayling by birds 

and mammals. Such predation likely 

does occur, but in contrast to the pattern 

of displacement observed concurrent 

with encroachment by nonnative trout, 

we are not aware of any situation where 

an increase in fish-eating birds or 

mammals has coincided with the 

decline of Arctic grayling. 

Consequently, the available information 

does not support a conclusion that 

predation by birds or mammals 

represents a substantial past, present, or 

foreseeable threat to native Arctic 

grayling in the upper Missouri River. 

D. Inadequacy of Existing Regulatory 

Mechanisms 

The ESA requires us to examine the 

adequacy of existing regulatory 

mechanisms with respect to those extant 

threats that place the species in danger 

of becoming either endangered or 

threatened. Thus, the scope of this 

analysis generally focuses on the extant 

native populations of Arctic grayling 

and potential current and foreseeable 

threats based on the inadequacy of 

existing regulatory mechanisms. 

Federal Laws and Regulations 

Native Arctic grayling are present in 

or adjacent to land managed by the U.S. 

Forest Service (USFS) (Big Hole River, 

Miner, and Mussigbrod Lakes: 

Beaverhead–Deerlodge National Forest), 

National Park Service (NPS) (Big Hole 

River: Big Hole National Battlefield), 

Bureau of Land Management (BLM) (Big 

Hole River: Dillon Resource Area), 

USFWS (Red Rock Lakes NWR); and the 

Federal Energy Regulatory Commission 

(Madison River–Ennis Reservoir: Ennis 

Dam, operated under Project 2188 

license). 

National Environmental Policy Act 

All Federal agencies are required to 

adhere to the National Environmental 

Policy Act (NEPA) of 1970 (42 U.S.C. 

4321 et seq.) for projects they fund, 

authorize, or carry out. The Council on 

Environmental Quality’s regulations for 

implementing NEPA (40 CFR 1500– 

1518) state that, when preparing 

environmental impact statements, 

agencies shall include a discussion on 

the environmental impacts of the 

various project alternatives, any adverse 

environmental effects which cannot be 

avoided, and any irreversible or 

irretrievable commitments of resources 

involved (40 CFR 1502). The NEPA 

itself is a disclosure law, and does not 

require subsequent minimization or 

mitigation measures by the Federal 

agency involved. Although Federal 

agencies may include conservation 

measures for Arctic grayling as a result 

of the NEPA process, any such measures 

are typically voluntary in nature and are 

not required by NEPA. 

Federal Land Policy and Management 

Act 

The BLM’s Federal Land Policy and 

Management Act (FLPMA) of 1976 (43 

U.S.C. 1701 et seq.), as amended, states 

that the public lands shall be managed 

in a manner that will protect the quality 

of scientific, scenic, historical, 

ecological, environmental, air and 

atmospheric, water resource, and 

archeological values. 

The BLM considers the fluvial Arctic 

grayling a sensitive species requiring 

special management consideration for 

planning and environmental analysis 

(BLM 2009b, entire). The BLM has 

recently developed a Resource 

Management Plan (RMP) for the Dillon 

Field Office Area that provides guidance 

for the management of over 900,000 

acres of public land administered by 

BLM in southwest Montana (BLM 

2006a, p. 2). The Dillon RMP area thus 

includes the geographic area that 

contains the Big Hole, Miner, 

Mussigbrod, Madison River, and Red 

Rock populations of Arctic grayling. A 

RMP planning area encompasses all 

private, State, and Federal lands within 

a designated geographic area (BLM 

2006a, p. 2), but the actual 

implementation of the RMP focuses on 

lands administered by the BLM that 

typically represent only a fraction of the 

total land area within that planning area 

(BLM 2006b, entire). Restoring Arctic 

grayling habitat and ensuring the longterm persistence of both fluvial and 

adfluvial ecotypes are among the RMP’s 

goals (BLM 2006a, pp. 30–31). However, 

there is little actual overlap between the 

specific parcels of BLM land managed 

by the Dillon RMP and the current 

distribution of Arctic grayling (BLM 

2006b, entire). 

The BLM also has a RMP for the Butte 

Field Office Area, which includes more 

than 300,000 acres in south-central 

Montana (BLM 2008, entire), including 

portions of the Big Hole River in 

Deerlodge and Silver Bow counties 

(BLM 2008, p. 8; 2009c, entire). The 

Butte RMP considers conservation and 

management strategies and agreements 

for Arctic grayling in its planning 

process and includes a goal to 

opportunistically enhance or restore 

habitat for Arctic grayling (BLM 2008, 

pp. 10, 30, 36). However, the Butte RMP 

does not mandate specific actions to 

improve habitat for Arctic grayling in 

the Big Hole River. 

National Forest Management Act 

Under the USFS’ National Forest 

Management Act (NFMA) of 1976, as 

amended (16 U.S.C. 1600–1614), the 

USFS shall strive to provide for a 

diversity of plant and animal 

communities when managing national 

forest lands. Individual national forests 

may identify species of concern that are 

significant to each forest’s biodiversity. 

The USFS Northern Rocky Mountain 

Region (R1) considers fluvial Arctic 

grayling a sensitive species (USFS 2004, 

entire) for which population viability is 

a concern, as evidenced by a significant 

downward trend in population or a 


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significant downward trend in habitat 

capacity. 

Much of the headwaters of the Big 

Hole River drainage are within the 

boundary of the Beaverhead–Deerlodge 

National Forest. The Miner and 

Mussigbrod Lakes Arctic grayling 

populations are entirely within Forest 

boundaries. The Beaverhead–Deerlodge 

National Forest is currently revising its 

forest plan. The USFS does not propose 

to designate key fish watersheds solely 

to benefit grayling, but fluvial Arctic 

grayling will remain a sensitive species 

with Forest-wide standards and 

objectives to meet the species’ habitat 

requirements (USFS 2009a, p. 19). With 

respect to fluvial Arctic grayling, the 

USFS is proposing a Controlled Surface 

Use (CSU) stipulation in the Ruby River 

(an ongoing reintroduction site) and 

certain tributaries of the Big Hole River 

(USFS 2009b, pp. 29, B-13) to avoid 

impacts from mineral, gas, and oil 

extraction (USFS 2009b, pp. 27–28). 

These CSU stipulations define the 

minimum extent of buffer areas adjacent 

to streams. In general, the preferred 

forest plan alternative (Alternative 6, 

USFS 2009a, p. 6) is deemed by the 

USFS to provide management direction 

designed to ensure the persistence of 

grayling populations Forest-wide, and to 

meet viability requirements of this 

species (USFS 2009a, p. 146). The forest 

plan revision has not yet been finalized 

through a record of decision (ROD), so 

we are unable to specifically evaluate its 

potential effect on native Arctic grayling 

populations. 

National Park Service Organic Act 

The NPS Organic Act of 1916 (16 

U.S.C. 1 et seq.), as amended, states that 

the NPS ‘‘shall promote and regulate the 

use of the Federal areas known as 

national parks, monuments, and 

reservations ... to conserve the scenery 

and the national and historic objects 

and the wild life therein and to provide 

for the enjoyment of the same in such 

manner and by such means as will leave 

them unimpaired for the enjoyment of 

future generations.’’ Native populations 

of Arctic grayling have been extirpated 

from Yellowstone National Park, but the 

Big Hole National Battlefield is adjacent 

to the North Fork of the Big Hole River 

(NPS 2006, entire), and Arctic grayling 

are occasionally encountered 

downstream from the Battlefield (Rens 

and Magee 2007, pp. 7, 13). 

Consequently, a very small amount of 

currently occupied grayling habitat is in 

the vicinity of lands managed by the 

NPS; therefore, the NPS Organic Act is 

not thought to have any significant 

effect on native Arctic grayling 

populations. 

National Wildlife Refuge System 

Improvement Act of 1997 

The National Wildlife Refuge Systems 

Improvement Act (NWRSIA) of 1997 

(Pub. L. 105-57) amends the National 

Wildlife Refuge System Administration 

Act of 1966 (16 U.S.C. 668dd et seq.). 

The NWRSIA directs the Service to 

manage the Refuge System’s lands and 

waters for conservation. The NWRSIA 

also requires monitoring of the status 

and trends of refuge fish, wildlife, and 

plants. The NWRSIA requires 

development of a Comprehensive 

Conservation Plan (CCP) for each refuge 

and management of each refuge 

consistent with its plan. 

The Service has developed a final 

CCP to provide a foundation for the 

management and use of Red Rock Lakes 

NWR (USFWS 2009, entire). Red Rocks 

NWR is 2,033-2,865 m (6,670-9,400 ft) 

above sea level, comprises 48,955 ac, 

and lies east of the Continental Divide 

near the uppermost reach of the 

Missouri drainage (USFWS 2009, pp. v, 

2). The Red Rocks NWR encompasses 

Lower and Upper Red Rock Lakes, 

which contain native grayling. The Red 

Rocks NWR CCP outlines a set of broad 

goals and specific objectives or 

strategies with respect to conservation 

of Arctic grayling that focuses on habitat 

improvements, reestablishment of 

populations, and removal of nonnative 

trout where necessary (USFWS 2009, 

pp. 67, 75–76). We expect that 

implementation of the CCP during the 

next 15 years will address a number of 

significant resource issues that affect 

grayling (e.g., riparian habitat condition, 

entrainment in irrigation ditches, 

increasing the extent of occupancy in 

the system). Nonetheless, actions 

similar to those planned inside the 

NWR will be needed on adjacent 

properties to reduce threats to the 

existing population of grayling in the 

Red Rock Lakes system. 

Federal Power Act 

The Federal Power Act of 1920 (16 

U.S.C. 791-828c, as amended) provides 

the legal authority for the Federal 

Energy Regulatory Commission (FERC), 

as an independent agency, to regulate 

hydropower projects. In deciding 

whether to issue a license, FERC is 

required to give equal consideration to 

mitigation of damage to, and 

enhancement of, fish and wildlife (16 

U.S.C. 797(e)). A number of FERClicensed dams exist in the Missouri 

River basin in current (i.e., Ennis Dam 

on the Madison River) and historical 

Arctic grayling habitat (e.g., Hebgen 

Dam on the Madison River; Hauser, 

Holter, and Toston dams on the 

mainstem Missouri River; and Clark 

Canyon Dam on the Beaverhead River). 

The FERC license expiration dates for 

these dams range from 2024 (Toston) to 

2059 (Clark Canyon) (FERC 2010, 

entire). None of these structures provide 

upstream passage of fish, and such dams 

are believed to be one of the primary 

factors leading to the decline of Arctic 

grayling in the Missouri River basin (see 

discussion under Factor A, above). 

Consequently, we conclude that 

historically the Federal Power Act has 

not adequately protected Arctic grayling 

or its habitat. We anticipate this will 

remain a threat it in the foreseeable 

future because of future expiration dates 

of the FERC-licensed dams in the upper 

Missouri River basin. 

Clean Water Act 

The Clean Water Act (CWA) of 1972 

(33 U.S.C. 1251 et seq.) establishes the 

basic structure for regulating discharges 

of pollutants into the waters of the 

United States and regulating quality 

standards for surface waters. The CWA’s 

general goal is to ‘‘restore and maintain 

the chemical, physical, and biological 

integrity of the Nation’s waters’’ (33 

U.S.C. 1251 (a)). The CWA requires 

States to adopt standards for the 

protection of surface water quality and 

establishment of Total Maximum Daily 

Load (TMDL) guidelines for rivers. The 

Big Hole River has approved TMDL 

plans for its various reaches (MDEQ 

2009a, entire; 2009b, entire); thus, 

complete implementation of this plan 

should improve water quality (by 

reducing water temperatures, and 

reducing sediment and nutrient inputs) 

in the Big Hole River in the foreseeable 

future. As of November 2009, the Red 

Rocks watershed was in the pre-TMDL 

planning and assessment phase, but 

there was no significant TMDL plan 

development activity in the Madison 

River (see MDEQ 2010). Consequently, 

implementation of the CWA through an 

EPA-approved TMDL plan began in 

2009 for the Big Hole River watershed, 

but has yet to begin in other waters 

occupied by native Arctic grayling in 

the upper Missouri River. The CWA 

does not appear to be adequate to 

protect the Missouri River DPS of Arctic 

grayling, but implementation of TMDL 

plans should improve habitat conditions 

for Big Hole River grayling in the 

foreseeable future. 

Montana State Laws and Regulations 

Arctic grayling is considered a species 

of special concern by Montana, but this 

is not a statutory or regulatory 

classification (Montana Natural Heritage 

Program 2010). 


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State Comprehensive Wildlife 

Conservation Strategies 

These strategies, while not State or 

national legislation, can help prioritize 

conservation actions within each State. 

Species and habitats named within each 

Comprehensive Wildlife Conservation 

Strategy (CWCS) may receive focused 

attention. The MFWP considers Arctic 

grayling as a Tier I conservation species 

under its CWCS and the Big Hole River 

also is a Tier I Aquatic Conservation 

Focus Area (Montana’s Comprehensive 

Fish and Wildlife Conservation Strategy 

(MCFWCS) 2005, pp. 75–76). 

Montana Environmental Policy Act 

The legislature of Montana enacted 

the Montana Environmental Policy Act 

(MEPA) as a policy statement to 

encourage productive and enjoyable 

harmony between humans and their 

environment, to protect the right to use 

and enjoy private property free of undue 

government regulation, to promote 

efforts that will prevent or eliminate 

damage to the environment and 

biosphere and stimulate the health and 

welfare of humans, to enrich the 

understanding of the ecological systems 

and natural resources important to the 

State, and to establish an environmental 

quality council (MCA 75-1-102). Part 1 

of the MEPA establishes and declares 

Montana’s environmental policy. Part 1 

has no legal requirements, but the 

policy and purpose provide guidance in 

interpreting and applying statutes. Part 

2 requires State agencies to carry out the 

policies in Part 1 through the use of 

systematic, interdisciplinary analysis of 

State actions that have an impact on the 

human environment. This is 

accomplished through the use of a 

deliberative, written environmental 

review. In practice, MEPA provides a 

basis for the adequate review of State 

actions in order to ensure that 

environmental concerns are fully 

considered (MCA 75-1-102). Similar to 

NEPA, the MEPA is largely a disclosure 

law and a decision-making tool that 

does not specifically require subsequent 

minimization or mitigation measures. 

Laws Affecting Physical Aquatic 

Habitats 

A number of Montana State laws have 

a permitting process applicable to 

projects that may affect stream beds, 

river banks, or floodplains. These 

include the Montana Stream Protection 

Act (SPA), the Streamside Management 

Zone Law (SMZL), and the Montana 

Natural Streambed and Land 

Preservation Act (Montana Department 

of Natural Resources (MDNRC) 2001, 

pp. 7.1–7.2). The SPA requires that a 

permit be obtained for any project that 

may affect the natural and existing 

shape and form of any stream or its 

banks or tributaries (MDNRC 2001, p. 

7.1). The Montana Natural Streambed 

and Land Preservation Act (i.e., 

MNSLPA or 310 permit) requires 

private, nongovernmental entities to 

obtain a permit for any activity that 

physically alters or modifies the bed or 

banks of a perennially-flowing stream 

(MDNRC 2001, p. 7.1). The SPA and 

MNSLPA laws do not mandate any 

special recognition for species of 

concern, but in practice, biologists that 

review projects permitted under these 

laws usually stipulate restrictions to 

avoid harming such species (Horton 

2010, pers. comm.). The SMZL regulates 

forest practices near streams (MDNRC 

2001, p. 7.2). The Montana Pollutant 

Discharge Elimination System (MPDES) 

Stormwater Permit applies to all 

discharges to surface water or 

groundwater, including those related to 

construction, dewatering, suction 

dredges, and placer mining, as well as 

to construction that will disturb more 

than 1 acre within 100 ft (30.5 m) of 

streams, rivers, or lakes (MDNRC 2001, 

p. 7.2). 

Review of applications by MFWP, 

MTDEQ, or MDNRC is required prior to 

issuance of permits under the above 

regulatory mechanisms (MDNRC 2001, 

pp. 7.1–7.2). Although these regulatory 

mechanisms would be expected to limit 

impacts to aquatic habitats in general, 

the decline of Arctic grayling in the Big 

Hole River, Madison River, and certain 

waters in the Red Rock Lakes system 

does not provide evidence that past 

implementation of these laws, 

regulations, and permitting processes 

has effectively limited impacts to Arctic 

grayling habitat. Thus, we have no basis 

for concluding that these same 

regulatory mechanisms are adequate to 

protect the Arctic grayling and its 

habitat now or in the foreseeable future. 

Montana Water Use Act 

The implementation of Montana 

Water Use Act (Title 85: Chapter 2, 

Montana Codes Annotated) may not 

adequately address threats to Arctic 

grayling in basins where the allocation 

of water rights exceeds the available 

water (overallocation) and the water 

rights holders fully execute their rights 

(i.e., use all water legally available for 

diversion). The Missouri River system is 

generally believed to be 

overappropriated, and water for 

additional consumptive uses is only 

available for a few months during very 

wet years (MDNRC 1997, p. 12). The 

Upper Missouri River basin and 

Madison River basin have been closed 

to new water appropriations because of 

water availability problems, 

overappropriation, and a concern for 

protecting existing water rights (MDNRC 

2009, p. 45). In addition, recent 

compacts (a legal agreement between 

Montana, a Federal agency, or an Indian 

tribe determining the quantification of 

federally or tribally claimed water 

rights) have been signed that close 

appropriations in specific waters in or 

adjacent to Arctic grayling habitats. For 

example, the USFWS–Red Rock Lakes– 

Montana Compact includes a closure of 

appropriations for consumptive use in 

the drainage basins upstream of the 

most downstream point on the Red Rock 

Lakes NWR and the Red Rock Lakes 

Wilderness Area (MDNRC 2009, pp. 18, 

47). The NPS–Montana Compact 

specifies that certain waters will be 

closed to new appropriations when the 

total appropriations reach a specified 

level, and it applies to Big Hole National 

Battlefield and adjacent waters (North 

Fork of the Big Hole River and its 

tributaries including Ruby and Trail 

Creeks), and the portion of Yellowstone 

National Park that is in Montana 

(MDNRC 2009, p. 48). 

The State of Montana is currently 

engaged in a state-wide effort to 

adjudicate (finalize) water rights 

claimed before July 1, 1973. The final 

product of adjudication in a river basin 

is a final decree. To reach completion, 

a decree progresses through several 

stages: (1) Examination, (2) temporary 

preliminary decree, (3) preliminary 

decree, (4) public notice, (5) hearings, 

and (6) final decree (MDNRC 2009, pp. 

9–14). As of February 2010, the Red 

Rock River system is currently being 

examined, and the Big Hole and 

Madison Rivers have temporary decrees 

(MDNRC 2010, entire). We anticipate 

the final adjudication of all the river 

basins in Montana that currently 

contain native Arctic grayling will be 

completed in the foreseeable future, but 

we do not know if this process will 

eliminate the overallocation of water 

rights. 

Fishing Regulations 

Arctic grayling is considered a game 

fish (MFWP 2010, p. 16), but is subject 

to special catch-and-release regulations 

in streams and rivers within its native 

range (MFWP 2010, p. 52). Catch-andrelease regulations also are in effect for 

Ennis Reservoir on the Madison River 

(MFWP 2010, p. 61). Arctic grayling in 

Miner and Mussigbrod Lakes are subject 

to more liberal regulations; anglers can 

keep up to 5 per day and have up to 10 

in possession in accordance with 

standard daily and possession limits for 

that angling management district 


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(MFWP 2010, p. 52). We have no 

evidence to indicate that current fishing 

regulations are inadequate to protect 

native Arctic grayling in the Missouri 

River basin (see discussion under Factor 

B, above). 

Summary of Factor D 

We infer that current Federal and 

State regulatory mechanisms are 

inadequate to protect native Arctic 

grayling of the upper Missouri River. 

We conclude this because the regulatory 

mechanisms may only apply to specific 

populations (or parts of populations) 

depending on land ownership and 

jurisdiction, they have no track record 

of addressing significant threats to 

habitat, and they do not address the 

threat posed by nonnative trout. 

Regulatory mechanisms on Federal 

lands may be adequate to protect certain 

fragments of Arctic grayling habitat or 

isolated populations (e.g., Miner and 

Mussigbrod Lakes). However, the 

extirpation of more than one lake 

population within the Beaverhead– 

Deerlodge National Forest (e.g., Elk Lake 

– Oswald 2000, p. 10; Hamby Lake – 

Oswald 2005a, pers. comm.) suggests 

the existing regulatory mechanisms may 

not be sufficient. Difficulties in 

coordinating land and water use across 

jurisdictional boundaries (State, 

Federal, private) within a watershed 

also present challenges for coordinated 

management of Arctic grayling. In the 

Big Hole River, fluvial Arctic grayling 

generally occupy waters adjacent to 

private lands (MFWP et al. 2006, p. 13; 

Lamothe et al. 2007, p. 4), so Federal 

regulations may have limited scope to 

protect the species. 

Conceivably, application of existing 

regulations concerning occupied Arctic 

grayling habitat in the upper Missouri 

River basin (e.g., CWA, FLPMA, NFMA, 

SMZL, SPA) should promote and ensure 

the persistence of Arctic grayling 

because these regulations were 

promulgated, to some extent, to limit 

impacts of human activity on the 

environment. However, based on the 

current status of the DPS and the 

degradation of habitat and declines in 

populations observed in the past 20 to 

30 years, during which time many of the 

above regulatory mechanisms have been 

in place, we have no basis to conclude 

that they have adequately protected 

grayling up to this time. In other words, 

existing regulations theoretically limit 

threats to Arctic grayling, but in practice 

have not done so. We suspect that 

incomplete or inconsistent application 

of these regulatory mechanisms and 

jurisdictional difficulties (State vs. 

Federal regulations, private vs. public 

lands) relative to the distribution of 

Arctic grayling may be partially 

responsible. Other regulatory 

mechanisms simply require disclosure 

(e.g., NEPA) and do not necessarily 

mandate protection for a species or its 

habitat. Consequently, we believe that 

existing regulatory mechanisms that 

deal with land and water management 

have not demonstrably reduced threats 

to Arctic grayling in the past, and we 

have no basis to conclude that they are 

adequate now or will be in the future. 

Existing regulatory mechanisms do 

not directly address threats posed by 

nonnative brook trout, brown trout, or 

rainbow trout (see Factor C discussion, 

above). One exception is that the Red 

Rock Lakes NWR CCP does consider 

removal of nonnative trout to be a 

possible action to benefit Arctic 

grayling, but this may not apply to 

occupied habitat outside the NWR, so 

the CCP is likely to only address this 

threat for a portion of the population. 

For the reasons described above, we 

conclude that the inadequacy of existing 

regulatory mechanisms poses a current 

threat to native Arctic grayling of the 

upper Missouri River. We do not 

anticipate any changes to the existing 

regulatory mechanisms, thus we 

conclude that the inadequacy of existing 

regulatory mechanisms is a threat in the 

foreseeable future. 

E. Other Natural or Manmade Factors 

Affecting Its Continued Existence 

Drought 

Drought appears to be a significant 

natural factor that threatens Arctic 

grayling populations in streams and 

rivers in the upper Missouri River basin. 

Drought can affect fish populations by 

reducing stream flow volumes. This 

leads to dewatering and high 

temperatures that can limit connectivity 

among spawning, rearing, and sheltering 

habitats; to a reduced volume of 

thermally suitable habitat; and to an 

increased frequency of water 

temperatures above the physiological 

limits for optimum growth and survival 

in Arctic grayling. Drought is a natural 

occurrence in the interior western 

United States (see National Drought 

Mitigation Center 2010). The duration 

and severity of drought in Montana 

appears to have increased during the 

last 50 years, and precipitation has 

tended to be lower than average in the 

last 20 years (National Climatic Data 

Center 2010). In addition, drought can 

interact with human-caused stressors 

(e.g., irrigation withdrawals, riparian 

habitat degradation) to further reduce 

stream flows and increase water 

temperatures. 

Reduced stream flows and elevated 

water temperatures during drought have 

been most apparent in the Big Hole 

River system (Magee and Lamothe 2003, 

pp. 10-14; Magee et al. 2005, pp. 23-25; 

Rens and Magee 2007, pp. 11-12, 14). 

Although the response of stream and 

river habitats to drought is expected to 

be most pronounced because of the 

strong seasonality of flows in those 

habitats, effects in lake environments do 

occur. For example, both the Upper and 

Lower Red Rock Lakes are very shallow 

(Mogen 1996, p. 7). Reduced water 

availability during drought would result 

in further shallowing (loss of habitat 

volume) that can lead to increased 

temperatures in summer and the 

likelihood of complete freezing or 

anoxia (lack of oxygen) in winter. 

In the Big Hole River, evidence for the 

detrimental effects of drought on Arctic 

grayling populations is primarily 

inferential; observed declines in fluvial 

Arctic grayling and nonnative trout 

abundances in the Big Hole River 

coincide with periods of drought (Magee 

and Lamothe 2003, pp. 22–23, 28) and 

fish kills (Byorth 1995, pp. 10–11, 31). 

Similarly, lack of success with fluvial 

Arctic grayling restoration efforts 

elsewhere in the upper Missouri River 

basin also has been attributed, in part, 

to drought (Lamothe and Magee 2004a, 

p. 28). 

Given the climate of the 

intermountain West, we conclude that 

drought has been and will continue to 

be a natural occurrence. We assume that 

negative effects of drought on Arctic 

grayling populations, such as reduced 

connectivity among habitats or 

increased water temperatures at or 

above physiological thresholds for 

growth and survival, are more frequent 

in stream and river environments and in 

very shallow lakes relative to larger, 

deeper lakes. Therefore, we expect the 

threat of drought to be most pronounced 

for Arctic grayling populations in the 

Big Hole River, Madison River–Ennis 

Reservoir, and Red Rock Lakes. We do 

not know whether drought has or is 

currently limiting Arctic grayling 

populations in Miner and Mussigbrod 

Lakes, as there are few monitoring data 

for these populations. Arctic grayling in 

Miner and Mussigbrod Lakes 

presumably use inlet or outlet streams 

for spawning; thus, if severe drought 

occurs during spawning and before 

subsequent emigration of YOY grayling 

to the rearing lakes, then populationlevel effects are possible. Overall, we 

conclude that drought has been a past 

threat, is a current threat, and will 

continue to be a threat to Arctic grayling 

of the upper Missouri River basin, 

especially for those populations in the 


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Big Hole River, Madison River–Ennis 

Reservoir, and Red Rock Lakes. 

Successful implementation of the Big 

Hole Grayling CCAA may partially 

ameliorate the effects of drought in the 

Big Hole River, by reducing the 

likelihood that human-influenced 

actions or outcomes (irrigation 

withdrawals, destruction of riparian 

habitats, and fish passage barriers) will 

interact with the natural effects of 

drought (reduced stream flows and 

increased water temperatures) to 

negatively affect suitable habitat for 

Arctic grayling. We expect the 

magnitude of the threat from drought to 

increase in the foreseeable future under 

the anticipated air temperature and 

precipitation trends projected by 

climate change models (discussed in 

detail below). 

Climate Change 

Climate is influenced primarily by 

long-term patterns in air temperature 

and precipitation. The 

Intergovernmental Panel on Climate 

Change (IPCC) has concluded that 

climate warming is unequivocal, and is 

now evident from observed increases in 

global average air and ocean 

temperatures, widespread melting of 

snow and ice, and rising global mean 

sea level (IPCC 2007, pp. 30–31). 

Continued greenhouse gas emissions at 

or above current rates are expected to 

cause further warming (IPCC 2007, p. 

30). Eleven of the 12 years from 1995 

through 2006 rank among the 12 

warmest years in the instrumental 

record of global average near-surface 

temperature since 1850 (ISAB 2007, p.7; 

IPCC 2007, p. 30). During the last 

century, mean annual air temperature 

increased by approximately 0.6 °C (1.1 

°F) (IPCC 2007, p. 30). Warming appears 

to be accelerating in recent decades, as 

the linear warming trend over the 50 

years from 1956 to 2005 (average 0.13 °C 

or 0.24 °F per decade) is nearly twice 

that for the 100 years from 1906 to 2005 

(IPCC 2007, p. 30). Climate change 

scenarios estimate that the mean air 

temperature could increase by over 3 °C 

(5.4 °F) by 2100 (IPCC 2007, pp. 45–46). 

The IPCC also projects that there will 

likely be regional increases in the 

frequency of hot extremes, heat waves, 

and heavy precipitation, as well as 

greater warming in high northern 

latitudes (IPCC 2007, p. 46). We 

recognize that there are scientific 

differences of opinion on many aspects 

of climate change, including the role of 

natural variability in climate. In our 

analysis, we rely primarily on synthesis 

documents (IPCC 2007; ISAB 2007; Karl 

et al. 2009) that present the consensus 

view of a large number of experts on 

climate change from around the world. 

We found that these synthesis reports, 

as well as the scientific papers used in 

those reports, or resulting from those 

reports, represent the best available 

scientific information we can use to 

inform our decision. Where possible, we 

used empirical data or projections 

specific to the western United States, 

which includes the range of Arctic 

grayling in the Missouri River basin, 

and focused on observed or expected 

effects on aquatic systems. 

Water temperature and hydrology 

(stream flow) are sensitive to climate 

change, and influence many of the basic 

physical and biological processes in 

aquatic systems. For ectothermic 

organisms like fish, temperature sets 

basic constraints on species’ 

distribution and physiological 

performance, such as activity and 

growth (Coutant 1999, pp. 32–52). 

Stream hydrology not only affects the 

structure of aquatic systems across 

space and time, but influences the lifehistory and phenology (timing of lifecycle events) of aquatic organisms, such 

as fishes. For example, the timing of 

snowmelt runoff can be an 

environmental cue that triggers 

spawning migrations in salmonid fishes 

(Brenkman et al. 2001, pp. 981, 984), 

and the timing of floods relative to 

spawning and emergence can strongly 

affect population establishment and 

persistence (Fausch et al. 2001, pp. 

1438, 1450). Significant trends in water 

temperature and stream flow have been 

observed in the western United States 

(Stewart et al. 2005, entire; Kaushal et 

al. 2010, entire), and climatic forcing 

caused by increased air temperatures 

and changes in precipitation are 

partially responsible. 

Warming patterns in the western 

United States are not limited to streams. 

In California and Nevada, water surface 

temperatures have increased by an 

average of 0.11 °C (0.2 °F) per year since 

1992 and at a rate twice that of the 

average minimum air surface 

temperature (Schneider et al. 2009, p. 

L22402). In the western United States, 

runoff from snowmelt occurs 1 to 4 

weeks earlier (Regonda et al. 2005, p. 

380; Stewart et al. 2005, pp. 1136, 1141; 

Hamlett et al. 2007, p. 1468), 

presumably as a result of increased 

temperatures (Hamlet et al. 2007, p. 

1468), increased frequency of melting 

(Mote et al. 2005, p. 45), and decreased 

snowpack (Mote et al. 2005, p. 41). 

Trends in decreased water availability 

also are apparent across the Pacific 

Northwest. For example, Luce and 

Holden (2009, entire) found a tendency 

toward more extreme droughts at 72 

percent of the stream flow gages they 

examined across Idaho, Montana, 

Oregon, and Washington. 

Climate forcing may be directly or 

indirectly altering those habitats. Longterm water temperature data are not 

available for sites currently occupied by 

native Arctic grayling populations (e.g., 

Big Hole River, Red Rock Creek); 

however, if trends in air temperature are 

consistently related to increases in 

water temperature (Isaak et al. 2010, p. 

1), then a regional pattern of increased 

water temperature is likely, and it is 

reasonable to assume that Arctic 

grayling in the Big Hole River, Red Rock 

Creek, and Madison River near Ennis 

Reservoir also have experienced the 

same trend. Mean annual air 

temperature recorded at Lakeview, 

Montana, near the Red Rock Lakes 

between 1948 and 2005 did not increase 

significantly, although mean 

temperatures in March and April did 

show a statistically significant increase 

consistent with earlier spring warming 

observed elsewhere in North America 

during recent decades (USFWS 2009, 

pp. 36–39). 

The effect of such warming would be 

similar to that described for increased 

temperatures associated with stream 

dewatering (see discussion under Factor 

A), namely there has been an increased 

frequency of high water temperatures 

that may be above the physiological 

limits for survival or optimal growth for 

Arctic grayling, which is considered a 

cold-water (stenothermic) species 

(Selong et al. 2001, p. 1032). Changes in 

water temperature also may influence 

the distribution of nonnative trout 

species (Rahel and Olden 2008, p. 524) 

and the outcome of competitive 

interactions between those species and 

Arctic grayling. Brown trout are 

generally considered to be more tolerant 

of warm water than many salmonid 

species common in western North 

America (Coutant 1999, pp. 52–53; 

Selong et al. 2001, p. 1032), and higher 

water temperatures may favor brown 

trout where they compete against 

salmonids with lower thermal 

tolerances (Rahel and Olden 2008, p. 

524). Recently observed increases in the 

abundance and distribution of brown 

trout in the upper reaches of the Big 

Hole River may be consistent with the 

hypothesis that stream warming is 

facilitating encroachment. Further study 

is needed to evaluate this hypothesis. 

Observations on flow timing in the 

Big Hole River, upper Madison River, 

and Red Rock Creek indicate a tendency 

toward earlier snowmelt runoff (USFWS 

2010b). These hydrologic alterations 

may be biologically significant for 

Arctic grayling in the Missouri River 

basin because they typically spawn 


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prior to the peak of snowmelt runoff 

(Shepard and Oswald 1989, p. 7; Mogen 

1996, pp. 22–23; Rens and Magee 2007, 

pp. 6–7). A trend toward earlier 

snowmelt runoff could thus result in 

earlier average spawning dates, with 

potential (and presently unknown) 

implications for spawning success and 

growth and survival of fry. Water 

availability has measurably decreased in 

some watersheds occupied by Arctic 

grayling. For example, mean annual 

precipitation recorded at Lakeview, 

Montana, near the Red Rock Lakes, 

decreased significantly between 1948 

and 2005 (USFWS 2009, pp. 36–39). 

The western United States appears to 

be warming faster than the global 

average. In the Pacific Northwest, 

regionally averaged temperatures have 

risen 0.8 °C (1.5 °F) over the last century 

and as much as 2 °C (4 °F) in some 

areas. They are projected to increase by 

another 1.5 to 5.5 °C (3 to 10 °F) over 

the next 100 years (Karl et al. 2009, p. 

135). For the purposes of this finding, 

we consider the foreseeable future for 

anticipated climate changes as 

approximately 40 years, because various 

global climate models (GCM) and 

emissions scenarios give consistent 

predictions within that timeframe (Ray 

et al. 2010, p. 11). We used a similar 

foreseeable future to consider climate 

change projects in other 12–month 

findings (see American pika (Ochotona 

princeps) – 75 FR 6448, February 9, 

2010). While projected patterns of 

warming across North America are 

generally consistent across different 

GCMs and emissions scenarios (Ray et 

al. 2010, p. 22), there tends to be less 

agreement among models for whether 

mean annual precipitation will increase 

or decrease, but the models seem to 

indicate an increase in precipitation in 

winter and a decrease in summer (Ray 

et al. 2010, pp. 22–23). In the 

foreseeable future, natural variation will 

likely confound a clear prediction for 

precipitation based on current climate 

models (Ray et al. 2010, p. 29). 

Although there is considerable 

uncertainty about how climate will 

evolve at any specific location, 

statistically downscaled climate 

projection models (models that predict 

climate at finer spatial resolution than 

GCMs) for the Pacific Northwest also 

support widespread warming, with 

warmer temperature zones shifting to 

the north and upward in elevation (Ray 

et al. 2010, pp. 23–24). 

The land area of the upper Missouri 

River basin also is predicted to warm 

(Ray et al. 2010, p. 23), although 

currently occupied Arctic grayling 

habitat tends be in colder areas of 

moderate-to-high elevation. Four out of 

five populations are at approximately 

1,775 to 2,125 m (5,860 to 7,012 ft) 

(Peterson and Ardren 2009, p. 1761). 

Presumably, any existing trends in 

water temperature increase and earlier 

snowmelt runoff in streams and rivers 

that is being forced by increases in air 

temperature should continue. To the 

extent that these trends in water 

temperature and hydrology already exist 

in habitats occupied by native Arctic 

grayling, they should continue into the 

foreseeable future. In general, climate 

change is expected to substantially 

reduce the thermally suitable habitat for 

coldwater fish species (Keleher and 

Rahel 1996, pp. 1, 6–11; Mohseni et al. 

2003, pp. 389, 401; Flebbe et al. 2006, 

p. 1371, 1378; Rieman et al. 2007, pp. 

1552, 1559). The range of native Arctic 

grayling in the upper Missouri River has 

already contracted significantly during 

the past 50 to 100 years (Vincent 1962, 

pp. 96–121; Kaya 1992, pp. 49–51). The 

currently occupied native Arctic 

grayling habitat tends be in colder areas 

of moderate-to-high elevation that may, 

to some extent, be more resistant to 

large or rapid changes in hydrology 

(Regonda et al. 2005, p. 380; Stewart et 

al. 2005, p. 1142) or perhaps stream 

warming. 

Nonetheless, we do not expect these 

habitats to be entirely immune from 

effects of climate warming, so we expect 

that climate change could lead to further 

range contractions of Arctic grayling of 

the upper Missouri River and may 

increase the species’ risk of extinction 

over the next 30 to 40 years as climate 

impacts interact with existing stressors 

(Karl et al. 2009, p. 81), such as habitat 

degradation, stream dewatering, 

drought, and interactions with 

nonnative trout that are already 

affecting the DPS. We anticipate that 

implementation of the Big Hole Grayling 

CCAA may partially compensate for, or 

reduce the severity of, likely effects of 

climate change on Arctic grayling in the 

Big Hole River. However, if current 

projections are realized, climate change 

is likely to exacerbate the existing 

primary threats to Arctic grayling 

outside the Big Hole River. The IPCC 

projects that the changes to the global 

climate system in the 21st century will 

likely be greater than those observed in 

the 20th century (IPCC 2007, p. 45); 

therefore, we anticipate that these 

effects will continue and likely increase 

into the foreseeable future. We do not 

consider climate change in and of itself 

to be a significant factor in our 

determination of whether Arctic 

grayling of the upper Missouri River is 

warranted for listing because of the 

greater imminence and magnitude of 

other threats (e.g., Factor A: habitat 

degradation, Factor C: nonnative trout). 

However, we expect the severity and 

scope of key threats (habitat degradation 

and fragmentation, stream dewatering, 

and nonnative trout) to increase in the 

foreseeable future because of climate 

change effects that are already 

measureable (i.e., increased water 

temperature, increased frequency of 

extreme drought, changes in runoff 

patterns). Thus, we consider that 

climate change will potentially intensify 

some of the significant current threats to 

all Arctic grayling populations in the 

DPS. After approximately 40 years, the 

variation in GCM projections based on 

the various emissions scenarios begins 

to increase dramatically (Ray et al. 2010 

pp. 12–13), so 40 years represents the 

foreseeable future in terms of the extent 

to which the effects of climate change (a 

major environmental driver) can reliably 

be modeled or predicted. Thus we 

conclude that climate change 

constitutes a threat in the Missouri DPS 

of Arctic grayling in the foreseeable 

future. 

Stochastic (Random) Threats 

A principle of conservation biology is 

that the presence of larger and more 

productive (resilient) populations can 

reduce overall extinction risk. To 

minimize extinction risk due to 

(random) stochastic threats, life-history 

diversity should be maintained, 

populations should not all share 

common catastrophic risks, and both 

widespread and spatially close 

populations are needed (Fausch et al. 

2006, p. 23; Allendorf et al. 1997, 

entire). Based on these principles, the 

upper Missouri River DPS of Arctic 

grayling may face current and future 

threats from stochastic processes that 

act on small, reproductively isolated 

populations. 

The upper Missouri River DPS of 

Arctic grayling exists as a collection of 

small, isolated populations (Figure 2; 

Peterson and Ardren 2009, entire). 

Patterns of dispersal among extant 

Arctic grayling populations have been 

constrained dramatically by the 

presence of dams. The inability of fish 

to move between populations limits 

genetic exchange, the maintenance of 

local populations (demographic 

support; Hilderbrand 2003, p. 257), and 

recolonization of habitat fragments 

(reviewed by Fausch et al. 2006, pp. 8- 

9). Isolated populations cannot offset 

the random loss of genetic variation 

(Fausch et al. 2006, p. 8). This in turn 

can lead to loss of phenotypic variation 

and evolutionary potential (Allendorf 

and Ryman 2002, p. 54). Relative to the 

presumed historical condition of 


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connectivity among most of the major 

rivers in the upper Missouri River basin, 

the extant native Arctic grayling 

populations face both genetic and 

demographic threats from isolation, 

both currently and in the foreseeable 

future. 

Four of the five individual 

populations in the upper Missouri River 

DPS of Arctic grayling are at low-tomoderate abundance (see Population 

Status and Trends for Native Arctic 

Grayling of the Upper Missouri River, 

above). Individually, small populations 

need to maintain enough adults to 

minimize loss of variability through 

genetic drift and inbreeding (Rieman 

and McIntyre 1993, pp. 10–11). The 

point estimates for genetic effective 

population sizes observed in the Big 

Hole River, Miner Lakes, Madison River, 

and Red Rock Lakes populations are 

above the level at which inbreeding is 

an immediate concern, but below the 

level presumed to provide the genetic 

variation necessary to conserve longterm adaptive potential (Peterson and 

Ardren 2009, pp. 1767, 1769). 

Historically, effective population sizes 

of Arctic grayling in the Missouri River 

were estimated to be 1 or 2 orders of 

magnitude greater (10 to 100 times) than 

those currently observed (Peterson and 

Ardren 2009, pp. 1767). Loss of genetic 

variation relative to the historical 

condition thus represents a threat to 

Arctic grayling in the foreseeable future. 

Only the Big Hole River population 

expresses the migratory fluvial ecotype 

that presumably dominated in the upper 

Missouri River basin (Kaya 1992, pp. 

47–50); therefore, the DPS lacks 

functional redundancy in ecotypes. 

Conservation of life-history diversity is 

important to the persistence of species 

confronted by habitat change and 

environmental perturbations (Beechie et 

al. 2006, entire). Therefore, the lack of 

additional fluvial populations 

represents a current threat to the upper 

Missouri River DPS. Reintroduction 

efforts have been ongoing to reduce this 

threat, but have not yet produced a selfsustaining population at any of the 

reintroduction sites (Rens and Magee 

2007, pp. 21–38). Future successful 

reintroductions may reduce this threat, 

but at the present time we consider the 

threat to extend into the foreseeable 

future. 

Populations of Arctic grayling in the 

upper Missouri River DPS are for the 

most part widely separated from one 

another, particularly those populations 

in the Big Hole, Madison, and Red Rock 

drainages (see Figure 2). Thus, they do 

not appear to all share a common risk 

of being extirpated by a rare, highmagnitude environmental disturbance 

(i.e., catastrophe). Three of the five 

populations are within the same 

watershed (Big Hole River, Miner Lakes, 

and Mussigbrod Lake populations), so 

collectively these three populations 

would be at greater risk. Individually, 

each population appears to be at 

substantial risk of extirpation by 

catastrophe from one or more factor, 

such as restricted distribution (Miner 

Lakes, Mussigbrod Lake), low 

population abundance (Madison Lake, 

Red Rocks Lakes , Big Hole River), and 

concentration of spawning primarily in 

a single, discrete location (Red Rock 

Lakes). The Big Hole River population 

may be at a comparatively lower risk 

from catastrophe because individuals 

still spawn at multiple locations within 

the drainage (Rens and Magee 2007, p. 

13). 

The population viability analysis 

(PVA) demonstrates that four of the five 

extant populations in the upper 

Missouri River DPS of Arctic grayling 

are at moderate (at least 13 percent) to 

high risk (more than 50 percent) of 

extinction from random environmental 

variation. In this context, random 

environmental variation is simply 

considered to be common 

environmental fluctuations, such as 

drought, floods, debris flows, changes in 

food availability, etc. that affect 

population size and population growth. 

These PVA analyses assume that 

variation in annual population growth 

increases as population size decreases 

(Rieman and McIntyre 1993, pp. 43–46), 

which seems a reasonable assumption 

given the large inter-annual variability 

in relative abundance and recruitment 

observed in some Arctic grayling 

populations in Montana (e.g., Big Hole 

River) (Magee et al. 2005, pp. 27–28). 

Simply stated, smaller populations are 

more likely to go extinct even if they are 

stable because they are already close to 

the extinction threshold, and random 

environmental events can drive their 

abundance below that threshold. 

Consequently, we believe that 

extinction risk from random 

environmental variation (droughts, 

floods, etc.) represents a significant 

threat in the foreseeable future based on 

the PVA. 

We are unsure whether chance 

variation in the fates of individuals 

within a given year (demographic 

stochasticity) is a current threat to the 

upper Missouri River DPS of Arctic 

grayling. The magnitude of demographic 

stochasticity is inversely related to 

population size (Morris and Doak 2002, 

pp. 22–23), but we do not know whether 

any of the Arctic grayling populations 

currently exist at or below an 

abundance where demographic 

stochasticity is likely. 

Overall, we conclude that the upper 

Missouri River DPS of Arctic grayling 

faces threats from population isolation, 

loss of genetic diversity, and small 

population size, which all interact to 

increase the likelihood that random 

environmental variation or a catastrophe 

can extirpate an individual population. 

The uncertainty of PVA predictions 

increases dramatically after about 25 to 

30 years, so we feel this represents a 

foreseeable future in terms of stochastic 

threats to the DPS. Lack of connectivity 

among extant populations and lack of 

replicate populations for the fluvial 

ecotype represent current threats. 

Threats from reduced genetic diversity, 

environmental variation, or catastrophe 

are threats in the foreseeable future, 

because their effects may take longer to 

play out (i.e., link between genetic 

diversity and adaptation) and are based 

on probabilistic inference concerning 

the magnitude of variation in 

population growth, environmental 

fluctuation, and periodic disturbance. 

Summary of Factor E 

Based on the information available at 

this time, we conclude that drought 

represents a current and future threat to 

native Arctic grayling in the upper 

Missouri River system. Drought can 

affect fish populations by reducing 

stream flow volumes, which leads to 

dewatering and high temperatures that 

can limit connectivity among spawning, 

rearing, and sheltering habitats; a 

reduced volume of thermally suitable 

habitat; and an increased frequency of 

water temperatures above the 

physiological limits for optimum growth 

and survival. 

Climate projections suggest that the 

frequency and severity of drought is 

expected to increase; thus the 

magnitude of drought-related threats 

and impacts also may increase. We 

anticipate the effects of drought to be 

most pronounced in streams, rivers, and 

shallow lakes; therefore, the Big Hole 

River, Madison River–Ennis Reservoir, 

and Red Rock Lakes populations are 

likely to be most threatened by drought. 

There is evidence for increasing air 

temperatures and changing hydrologic 

pattern resulting from climate change in 

the Pacific Northwest and 

intermountain West, and we conclude 

that climate change is a secondary threat 

that can interact with and magnify the 

effects of primary threats, such as 

drought, stream dewatering from 

irrigation withdrawals, and the outcome 

of interactions with nonnative trout 

species that have higher thermal 

tolerances. We anticipate that climate 


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change will remain a threat in the 

foreseeable future, but that conservation 

programs that increase connectivity 

among refuge habitats and improve 

stream flows (e.g., Big Hole Grayling 

CCAA) will to some extent mitigate or 

lessen the effects of climate change. 

Climate change effects should be most 

pronounced in those same habitats and 

populations most strongly affected by 

water availability (Big Hole River, 

Madison River–Ennis Reservoir, Red 

Rock Lakes), but lake habitats also can 

be affected (Schneider et al. 2009, 

entire), so threats likely extend to the 

other populations in the DPS (Miner 

and Mussigbrod Lakes). 

The Missouri River DPS of Arctic 

grayling currently exists as a collection 

of small, isolated populations that face 

some current and foreseeable threats 

from a collection of random (stochastic) 

processes characteristic of small 

populations, such as loss of genetic 

diversity because of habitat 

fragmentation and isolation, and 

individual populations face increased 

risk of extirpation from random 

environmental variation (results of PVA) 

and catastrophe. 

Finding 

As defined by the DPS Policy, we 

determined that the native Arctic 

grayling of the upper Missouri River 

constitutes a listable entity under the 

ESA. We also considered the 

appropriateness of listing separate 

distinct population segments based on 

each of the ecotypes (fluvial and 

adfluvial) that occur naturally in Arctic 

grayling populations in the Missouri 

River basin. The best scientific 

information indicates these ecotypes 

share a recent evolutionary history and 

the populations do not cluster 

genetically by life-history type. 

Maintaining life-history diversity 

increases the likelihood that a species 

(or DPS) will maintain both the genetic 

diversity and evolutionary flexibility to 

deal with future environmental 

challenges. Consequently we feel that 

preservation of both native ecotypes in 

their native habitats is essential to 

conservation of the DPS; thus we have 

determined that a single DPS that 

includes both ecotypes is most 

appropriate from both a practical 

management and conservation 

perspective. We refer to this DPS as the 

Missouri River DPS of Arctic grayling. 

As discussed above, we do not include 

the nonnative Arctic grayling in the 

DPS, based on intent of the Act, IUCN 

guidelines, and NMFS policy. The 

Service does not currently have a 

specific policy concerning nonnative 

species, therefore we will investigate 

this topic in more detail during the 

proposed rulemaking process. 

As required by the ESA, we 

considered the five factors in assessing 

whether the Missouri River DPS of 

Arctic grayling is endangered or 

threatened throughout all or a 

significant portion of its range. We 

carefully examined the best scientific 

and commercial information available 

regarding the past, present, and future 

threats faced by the DPS. We reviewed 

the petition, information available in 

our files, other available published and 

unpublished information, and we 

consulted with recognized species 

experts and other Federal, State, and 

tribal agencies. On the basis of the best 

scientific and commercial information 

available, we find that listing the DPS as 

endangered or threatened is warranted. 

We will make a determination on the 

status of the species as endangered or 

threatened when we do a proposed 

listing determination. However, as 

explained in more detail below (see 

Preclusion and Expeditious Progress 

section), an immediate proposal of a 

regulation implementing this action is 

precluded by higher priority listing 

actions, and progress is being made to 

add or remove qualified species from 

the Lists of Endangered and Threatened 

Wildlife and Plants. 

The historical range of Arctic grayling 

in the upper Missouri River basin has 

declined dramatically in the past 

century. The five remaining indigenous 

populations are isolated from one 

another by dams or other factors. 

Moreover, three of these five 

populations (Big Hole, Madison–Ennis, 

Red Rocks) appear to be at low 

abundance (perhaps no more than 650 

to 2,000 adults per population) and have 

declined in abundance during the past 

few decades. The Big Hole River 

contains the only remaining example of 

the fluvial ecotype in the DPS, and the 

effective number of breeding adults 

declined by half during the past 15 

years. Populations of Arctic grayling in 

two small lakes in the Big Hole River 

drainage (Miner and Mussigbrod) 

appear to be more abundant, and 

perhaps more secure than the other 

native populations. 

This status review identified threats 

to the DPS related to Factors A, C, D, 

and E (see Table 5). All populations face 

potential threats from competition with 

and predation by nonnative trout 

(Factor C) now and in the foreseeable 

future. The magnitude of this threat 

likely varies by Arctic grayling 

population, and is greater in locations 

where multiple species of nonnative 

trout are present, abundant, and 

comprise a large proportion of the 

salmonid biomass (e.g., Big Hole River, 

Madison River–Ennis Reservoir, Red 

Rock Lakes). Most populations face 

threats that result from the alteration of 

their habitats (Factor A), such as habitat 

fragmentation from large dams or 

smaller irrigation diversion structures, 

stream dewatering, high summer water 

temperatures, loss of riparian habitats, 

and entrainment in irrigation ditches 

(see Table 5). Severe drought (Factor E) 

likely affects all populations by 

reducing water availability and reducing 

the extent of thermally suitable habitat, 

but we presume the effects of drought 

are most pronounced for Arctic grayling 

that reside primarily in streams and 

rivers (Big Hole River) or shallow lakes 

(Madison River–Ennis Reservoir, Red 

Rock Lakes). We did not consider 

climate change (Factor E) in and of itself 

to be a significant current threat, but if 

current climate changes projections are 

realized, we expect that climate change 

will influence severity and scope of key 

threats (habitat degradation and 

fragmentation, stream dewatering, 

interactions with nonnative trout, 

drought). As applied, existing regulatory 

mechanisms (Factor D) do not appear to 

be adequate to address primary threats 

to grayling (e.g., stream dewatering, loss 

of riparian habitats), as at least three 

native Arctic grayling populations have 

continued to decline in abundance in 

recent decades. 


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TABLE 5. CURRENT AND FORESEEABLE THREATS TO INDIVIDUAL POPULATIONS OF NATIVE ARCTIC GRAYLING IN THE

UPPER MISSOURI RIVER DPS. 

Threat 

Factor Big Hole River Miner Lakes Mussigbrod Lake Madison River–Ennis Reservoir Red Rocks Lakes 

A Dams/habitat 

fragmentationa

Dewateringa

Thermal stressa

Entrainmenta

Riparian habitat lossa

Dams/habitat 

fragmentation 

Dams/habitat 

fragmentation 

Thermal stress 

Dams/habitat 

fragmentation 

Dewatering 

Thermal stress 

Entrainment 

Riparian habitat loss 

Sediments 

C Predation & competition 

with nonnative trout 

Predation & competition 

with nonnative trout 

Predation & competition 

with nonnative trout 

Predation & competition 

with nonnative trout 

Predation & competition 

with nonnative trout 

D Inadequate regulationsb

(nonnative trout, 

continued population 

decline) 

Inadequate regulationsb

(nonnative trout, 

extirpation of other lake 

populations of 

grayling) 

Inadequate regulationsb

(nonnative trout, 

extirpation of other lake 

populations of 

grayling) 

Inadequate regulationsb

(nonnative trout, 

federally-permitted dam, 

continued population 

decline) 

Inadequate regulationsb

(nonnative trout, 

continued population 

decline) 

E Reduced genetic 

diversity, low 

abundance, random 

events 

Drought 

Climate changec

No replicate of fluvial 

ecotype 

Reduced genetic 

diversity, low 

abundance, random 

events 

Drought 

Climate changec

Drought 

Climate changec

Reduced genetic 

diversity, low 

abundance, random 

events 

Drought 

Climate changec

Reduced genetic 

diversity, low 

abundance, random 

events 

Drought 

Climate changec

a The magnitude of current threats to the majority of the extant population or its habitat are expected be reduced in the foreseeable future from 

implementation of a formalized conservation plan (i.e., Big Hole Grayling CCAA). b Terms in parenthesis characterize the inadequacy of the regulatory mechanisms in terms of not addressing specific threats (e.g., nonnative 

trout, Factor C; dams, Factor A) or having no observed record of success with protecting existing populations (continued population decline, extirpation of other similarly situated populations). c Threats believed to be of secondary importance or that interact with primary threats. 

In the Big Hole River, ongoing 

implementation of a formalized 

conservation program (Big Hole 

Grayling CCAA) with substantial 

participation from non-Federal 

landowners and State and Federal 

agency partners should significantly 

reduce many of the habitat-related 

threats to that population in the 

foreseeable future. In the Red Rock 

Lakes NWR, implementation of a CCP 

should reduce many of the primary 

threats to Arctic grayling that occur 

within the NWR’s boundary, but threats 

to Arctic grayling and its habitat also 

exist outside the administrative 

boundary of the CCP. 

Four of five populations appear to be 

at risk of extirpation in the foreseeable 

future (next 20 to 30 years) from random 

fluctuations in environmental 

conditions (e.g., precipitation, food 

availability, density of competitors, 

etc.), simply because they are at low 

abundance and cannot receive 

demographic support from other native 

populations (Factor E). Low abundance 

and isolation also raises concerns that 

the loss of genetic variation from chance 

events (genetic drift) also may be a 

threat in some populations. Maintaining 

life-history diversity is important for 

species conservation given anticipated 

environmental challenges such as those 

anticipated under climate change, so 

having only a single population of the 

fluvial ecotype represents a significant 

threat to that ecotype’s long-term 

persistence. A reintroduction program 

designed to address this threat has been 

implemented for more than a decade 

and has made some recent technical 

advances in the production of Arctic 

grayling fry. Natural reproduction by 

grayling has been observed at a reintroduction site in the Ruby River. At 

least 5 to 10 more years of monitoring 

is needed for us to establish that the 

reintroduced fish in the Ruby River 

constitute a viable population. 

We reviewed the available 

information to determine if the existing 

and foreseeable threats render the 

species at risk of extinction now such 

that issuing an emergency regulation 

temporarily listing the species under 

section 4(b)(7) of the ESA is warranted. 

We determined that issuing an 

emergency regulation temporarily 

listing the DPS is not warranted at this 

time because there are five populations 

in the DPS and the probability of 

simultaneous extinction of all five 

populations is low, as the populations 

are physically discrete and isolated from 

one another such that a natural or 

human-caused catastrophe is not likely 

to extirpate all populations at once. In 

addition, the remaining population that 

expresses the fluvial ecotype (Big Hole 

River) is subject to ongoing 

implementation of a formalized 

conservation agreement (Big Hole 

Grayling CCAA) with adaptive 

management stipulations if Arctic 

grayling population goals are not being 

met (MFWP et al. 2006, pp. 60–61), and 

provisions to rescue Arctic grayling or 

address alteration to habitat in the event 

of a large-magnitude disturbance such 

as a debris flow or flood (MFWP 2006, 

pp. 85–86). 

Listing Priority Number 

The Service adopted guidelines on 

September 21, 1983 (48 FR 43098), to 

establish a rational system for utilizing 

available resources for the highest 

priority species when adding species to 

the Lists of Endangered or Threatened 

Wildlife and Plants or reclassifying 

species listed as threatened to 

endangered status. These guidelines, 

titled ‘‘Endangered and Threatened 

Species Listing and Recovery Priority 

Guidelines’’ address the immediacy and 

magnitude of threats, and the level of 

taxonomic distinctiveness by assigning 

priority in descending order to 


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monotypic genera (genus with one 

species), full species, and subspecies (or 

equivalently, distinct population 

segments of vertebrates). 

As a result of our analysis of the best 

available scientific and commercial 

information, we assigned the native 

Arctic grayling of the upper Missouri 

River a Listing Priority Number (LPN) of 

3 based on our finding that the DPS 

faces threats that are of high magnitude 

and are imminent. These primary 

threats include the present or threatened 

destruction, modification, or 

curtailment of its habitat; competition 

with and predation by nonnative trout; 

inadequacy of existing regulatory 

mechanisms to address all threats; 

extinction risk from small population 

size and isolation; drought; and lack of 

replication of the fluvial life history. 

Under the Service’s guidelines, the 

magnitude of threat is the first criterion 

we look at when establishing a listing 

priority. The guidance indicates that 

species with the highest magnitude of 

threat are those species facing the 

greatest threats to their continued 

existence. These species receive the 

highest listing priority. We consider the 

threats that the native Arctic grayling of 

the upper Missouri River faces to be 

high in magnitude because many of the 

threats that we analyzed are present 

throughout the range and currently 

impact the DPS to varying degrees (e.g., 

habitat fragmentation, nonnative trout, 

inadequate regulatory mechanisms), and 

will continue to impact the DPS into the 

future. The threats that are of high 

magnitude include present or 

threatened destruction, modification, or 

curtailment of its habitat; competition 

with and predation by nonnative trout; 

inadequacy of existing regulatory 

mechanisms to address all threats; 

extinction risk from small population 

size and isolation and vulnerability to 

catastrophes; drought; and lack of 

replication of the fluvial life-history. 

Also, the small number (five) and size 

and isolation of the populations may 

magnify the impact of the other threats 

under Factors A and C. 

The DPS consists of only five 

populations, so loss of any individual 

population would incrementally 

increase the risk that the DPS will not 

persist. However, we presume that loss 

of the Big Hole River population would 

create the highest risk, as this 

population contains much of the genetic 

diversity present in the species within 

the Missouri River basin (Peterson and 

Ardren 2009, pp. 1763, 1768, 1770) and 

is the only example of the fluvial 

ecotype. A conservation program (Big 

Hole Grayling CCAA) is being 

implemented to address habitat-related 

threats to the Big Hole River population, 

but the scope of the threat posed by 

nonnative trout remains high. Due to the 

scope and scale of the high magnitude 

threats and current isolation of already 

small populations, we conclude that the 

magnitude of threats to native Arctic 

grayling of the upper Missouri River is 

high. 

Under our LPN guidelines, the second 

criterion we consider in assigning a 

listing priority is the immediacy of 

threats. This criterion is intended to 

ensure that the species facing actual, 

identifiable threats are given priority 

over those for which threats are only 

potential or that are intrinsically 

vulnerable but are not known to be 

presently facing such threats. Not all the 

threats facing the DPS are imminent. For 

example, threats from climate change 

and catastrophe are reasonably certain 

to occur, and their effects may be 

particularly acute for small, isolated 

populations, but the specific nature and 

influence of these effects, although 

ongoing, are uncertain at this point. 

With relative certainty, we can project 

that climate change effects will 

exacerbate other ongoing effects 

throughout the DPS. In contrast, we 

have factual information that some 

threats are imminent because we have 

factual information that the threats are 

identifiable and that the DPS is 

currently facing them in many areas of 

its range. These other threats are 

covered in detail in the discussions 

under Factors A and C of this finding 

and include habitat fragmentation, 

stream dewatering, and riparian 

degradation from agriculture and 

ranching; dams; and competition with 

and predation by nonnative trout. 

Therefore, based on our LPN Policy, the 

threats are imminent (ongoing). 

The third criterion in our LPN 

guidelines is intended to devote 

resources to those species representing 

highly distinctive or isolated gene pools 

as reflected by taxonomy. We 

determined the native Arctic grayling of 

the upper Missouri River to be a valid 

DPS according to our DPS Policy. 

Therefore, under our LPN guidance, the 

native Arctic grayling of the upper 

Missouri River is assigned a lower 

priority than a species in a monotypic 

genus or a full species that faces the 

same magnitude and imminence of 

threats. Therefore, we assigned the 

native Arctic grayling of the upper 

Missouri River an LPN of 3 based on our 

determination that the DPS faces threats 

that are overall of high magnitude and 

are imminent. An LPN of 3 is the 

highest priority that can be assigned to 

a distinct population segment. We will 

continue to monitor the threats to the 

native Arctic grayling of the upper 

Missouri River, and the DPS’ status on 

an annual basis, and should the 

magnitude or the imminence of the 

threats change, we will revisit our 

assessment of LPN. 

Preclusion and Expeditious Progress 

Preclusion is a function of the listing 

priority of a species in relation to the 

resources that are available and 

competing demands for those resources. 

Thus, in any given fiscal year (FY), 

multiple factors dictate whether it will 

be possible to undertake work on a 

proposed listing regulation or whether 

promulgation of such a proposal is 

warranted but precluded by higher 

priority listing actions. 

The resources available for listing 

actions are determined through the 

annual Congressional appropriations 

process. The appropriation for the 

Listing Program is available to support 

work involving the following listing 

actions: Proposed and final listing rules; 

90–day and 12–month findings on 

petitions to add species to the Lists of 

Endangered and Threatened Wildlife 

and Plants (Lists) or to change the status 

of a species from threatened to 

endangered; annual determinations on 

prior ‘‘warranted but precluded’’ petition 

findings as required under section 

4(b)(3)(C)(i) of the ESA; critical habitat 

petition findings; proposed and final 

rules designating critical habitat; and 

litigation-related, administrative, and 

program-management functions 

(including preparing and allocating 

budgets, responding to congressional 

and public inquiries, and conducting 

public outreach regarding listing and 

critical habitat). The work involved in 

preparing various listing documents can 

be extensive and may include, but is not 

limited to: Gathering and assessing the 

best scientific and commercial data 

available and conducting analyses used 

as the basis for our decisions; writing 

and publishing documents; and 

obtaining, reviewing, and evaluating 

public comments and peer review 

comments on proposed rules and 

incorporating relevant information into 

final rules. The number of listing 

actions that we can undertake in a given 

year also is influenced by the 

complexity of those listing actions; that 

is, more complex actions generally are 

more costly. For example, during the 

past several years, the cost (excluding 

publication costs) for preparing a 12– 

month finding, without a proposed rule, 

has ranged from approximately $11,000 

for one species with a restricted range 

and involving a relatively 

uncomplicated analysis to $305,000 for 


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another species that is wide-ranging and 

involving a complex analysis. 

We cannot spend more than is 

appropriated for the Listing Program 

without violating the Anti-Deficiency 

Act (see 31 U.S.C. 1341(a)(1)(A)). In 

addition, in FY 1998 and for each FY 

since then, Congress has placed a 

statutory cap on funds which may be 

expended for the Listing Program, equal 

to the amount expressly appropriated 

for that purpose in that FY. This cap 

was designed to prevent funds 

appropriated for other functions under 

the ESA (for example, recovery funds 

for removing species from the Lists), or 

for other Service programs, from being 

used for Listing Program actions (see 

House Report 105-163, 105th Congress, 

1st Session, July 1, 1997). 

Recognizing that designation of 

critical habitat for species already listed 

would consume most of the overall 

Listing Program appropriation, Congress 

also put a critical habitat subcap in 

place in FY 2002 and has retained it 

each subsequent year to ensure that 

some funds are available for other work 

in the Listing Program: ‘‘The critical 

habitat designation subcap will ensure 

that some funding is available to 

address other listing activities’’ (House 

Report No. 107 - 103, 107th Congress, 1st 

Session, June 19, 2001). In FY 2002 and 

each year until FY 2006, the Service has 

had to use virtually the entire critical 

habitat subcap to address courtmandated designations of critical 

habitat, and consequently none of the 

critical habitat subcap funds have been 

available for other listing activities. In 

FY 2007, we were able to use some of 

the critical habitat subcap funds to fund 

proposed listing determinations for 

high-priority candidate species. In FY 

2009, while we were unable to use any 

of the critical habitat subcap funds to 

fund proposed listing determinations, 

we did use some of this money to fund 

the critical habitat portion of some 

proposed listing determinations so that 

the proposed listing determination and 

proposed critical habitat designation 

could be combined into one rule, 

thereby being more efficient in our 

work. In FY 2010, we are using some of 

the critical habitat subcap funds to fund 

actions with statutory deadlines. 

Thus, through the listing cap, the 

critical habitat subcap, and the amount 

of funds needed to address courtmandated critical habitat designations, 

Congress and the courts have in effect 

determined the amount of money 

available for other listing activities. 

Therefore, the funds in the listing cap, 

other than those needed to address 

court-mandated critical habitat for 

already listed species, set the limits on 

our determinations of preclusion and 

expeditious progress. 

Congress also recognized that the 

availability of resources was the key 

element in deciding, when making a 12– 

month petition finding, whether we 

would prepare and issue a listing 

proposal or instead make a ‘‘warranted 

but precluded’’ finding for a given 

species. The Conference Report 

accompanying Public Law 97-304, 

which established the current statutory 

deadlines and the warranted-butprecluded finding, states (in a 

discussion on 90–day petition findings 

that by its own terms also covers 12– 

month findings) that the deadlines were 

‘‘not intended to allow the Secretary to 

delay commencing the rulemaking 

process for any reason other than that 

the existence of pending or imminent 

proposals to list species subject to a 

greater degree of threat would make 

allocation of resources to such a petition 

[that is, for a lower-ranking species] 

unwise.’’ 

In FY 2010, expeditious progress is 

that amount of work that can be 

achieved with $10,471,000, which is the 

amount of money that Congress 

appropriated for the Listing Program 

(that is, the portion of the Listing 

Program funding not related to critical 

habitat designations for species that are 

already listed). However these funds are 

not enough to fully fund all our courtordered and statutory listing actions in 

FY 2010, so we are using $1,114,417 of 

our critical habitat subcap funds in 

order to work on all of our required 

petition findings and listing 

determinations. This brings the total 

amount of funds we have for listing 

actions in FY 2010 to $11,585,417. Our 

process is to make our determinations of 

preclusion on a nationwide basis to 

ensure that the species most in need of 

listing will be addressed first and also 

because we allocate our listing budget 

on a nationwide basis. The $11,585,417 

is being used to fund work in the 

following categories: compliance with 

court orders and court-approved 

settlement agreements requiring that 

petition findings or listing 

determinations be completed by a 

specific date; section 4 (of the ESA) 

listing actions with absolute statutory 

deadlines; essential litigation-related, 

administrative, and listing programmanagement functions; and highpriority listing actions for some of our 

candidate species. In 2009, the 

responsibility for listing foreign species 

under the ESA was transferred from the 

Division of Scientific Authority, 

International Affairs Program, to the 

Endangered Species Program. Starting 

in FY 2010, a portion of our funding is 

being used to work on the actions 

described above as they apply to listing 

actions for foreign species. This has the 

potential to further reduce funding 

available for domestic listing actions, 

although there are currently no foreign 

species issues included in our highpriority listing actions at this time. The 

allocations for each specific listing 

action are identified in the Service’s FY 

2010 Allocation Table (part of our 

administrative record). 

In FY 2007, we had more than 120 

species with an LPN of 2, based on our 

September 21, 1983, guidance for 

assigning an LPN for each candidate 

species (48 FR 43098). Using this 

guidance, we assign each candidate an 

LPN of 1 to 12, depending on the 

magnitude of threats (high vs. moderate 

to low), immediacy of threats (imminent 

or nonimminent), and taxonomic status 

of the species (in order of priority: 

monotypic genus (a species that is the 

sole member of a genus); species; or part 

of a species (subspecies, distinct 

population segment, or significant 

portion of the range)). The lower the 

listing priority number, the higher the 

listing priority (that is, a species with an 

LPN of 1 would have the highest listing 

priority). Because of the large number of 

high-priority species, we further ranked 

the candidate species with an LPN of 2 

by using the following extinction-risk 

type criteria: IUCN Red list status/rank, 

Heritage rank (provided by 

NatureServe), Heritage threat rank 

(provided by NatureServe), and species 

currently with fewer than 50 

individuals, or 4 or fewer populations. 

Those species with the highest IUCN 

rank (critically endangered), the highest 

Heritage rank (G1), the highest Heritage 

threat rank (substantial, imminent 

threats), and currently with fewer than 

50 individuals, or fewer than 4 

populations, comprised a group of 

approximately 40 candidate species 

(‘‘Top 40’’). These 40 candidate species 

have had the highest priority to receive 

funding to work on a proposed listing 

determination. As we work on proposed 

and final listing rules for these 40 

candidates, we are applying the ranking 

criteria to the next group of candidates 

with an LPN of 2 and 3 to determine the 

next set of highest priority candidate 

species. 

To be more efficient in our listing 

process, as we work on proposed rules 

for these species in the next several 

years, we are preparing multi-species 

proposals when appropriate, and these 

may include species with lower priority 

if they overlap geographically or have 

the same threats as a species with an 

LPN of 2. In addition, available staff 

resources also are a factor in 


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determining high-priority species 

provided with funding. Finally, 

proposed rules for reclassification of 

threatened species to endangered are 

lower priority, since as listed species, 

they are already afforded the protection 

of the ESA and implementing 

regulations. 

We assigned the upper Missouri River 

DPS of Arctic grayling an LPN of 3, 

based on our finding that the DPS faces 

immediate and high magnitude threats 

from the present or threatened 

destruction, modification, or 

curtailment of its habitat; competition 

with and predation by nonnative trout; 

and the inadequacy of existing 

regulatory mechanisms. One or more of 

the threats discussed above occurs in 

each known population in the Missouri 

River basin. These threats are ongoing 

and, in some cases (e.g., nonnative 

species), considered irreversible. Under 

our 1983 Guidelines, a ‘‘species’’ facing 

imminent high-magnitude threats is 

assigned an LPN of 1, 2, or 3, depending 

on its taxonomic status. Work on a 

proposed listing determination for the 

upper Missouri River DPS of Arctic 

grayling is precluded by work on higher 

priority candidate species (i.e., species 

with LPN of 2); listing actions with 

absolute statutory, court ordered, or 

court-approved deadlines; and final 

listing determinations for those species 

that were proposed for listing with 

funds from previous FYs. This work 

includes all the actions listed in the 

tables below under expeditious 

progress. 

As explained above, a determination 

that listing is warranted but precluded 

also must demonstrate that expeditious 

progress is being made to add or remove 

qualified species to and from the Lists 

of Endangered and Threatened Wildlife 

and Plants. (Although we do not discuss 

it in detail here, we also are making 

expeditious progress in removing 

species from the Lists under the 

Recovery program, which is funded by 

a separate line item in the budget of the 

Endangered Species Program. As 

explained above in our description of 

the statutory cap on Listing Program 

funds, the Recovery Program funds and 

actions supported by them cannot be 

considered in determining expeditious 

progress made in the Listing Program.) 

As with our ‘‘precluded’’ finding, 

expeditious progress in adding qualified 

species to the Lists is a function of the 

resources available and the competing 

demands for those funds. Given that 

limitation, we find that we are making 

progress in FY 2010 in the Listing 

Program. This progress included 

preparing and publishing the 

determinations presented in Table 6. 

TABLE 6. FY2010 COMPLETED LISTING ACTIONS

Publication Date Title Actions FR Pages 

10/08/2009 Listing Lepidium papilliferum (Slickspot Peppergrass) as a 

Threatened Species Throughout Its Range 

Final Listing, 

Threatened 

74 FR 52013-52064 

10/27/2009 90-day Finding on a Petition To List the American Dipper in the 

Black Hills of South Dakota as Threatened or Endangered 

Notice of 90–day Petition Finding, Not 

Substantial 

74 FR 55177-55180 

10/28/2009 Status Review of Arctic Grayling (Thymallus arcticus) in the Upper 

Missouri River System 

Notice of Intent to 

Conduct Status Review 

74 FR 55524-55525 

11/03/2009 Listing the British Columbia Distinct Population Segment of the 

Queen Charlotte Goshawk Under the ESA: Proposed rule. 

Proposed Listing 

Threatened 

74 FR 56757-56770 

11/03/2009 Listing the Salmon-Crested Cockatoo as Threatened Throughout 

Its Range with Special Rule 

Proposed Listing 

Threatened 

74 FR 56770-56791 

11/23/2009 Status Review of Gunnison sage-grouse (Centrocercus minimus) Notice of Intent to 

Conduct Status Review 

74 FR 61100-61102 

12/03/2009 12-Month Finding on a Petition to List the Black-tailed Prairie Dog 

as Threatened or Endangered 

Notice of 12–month 

Petition Finding, Not 

warranted 

74 FR 63343-63366 

12/03/2009 90-Day Finding on a Petition to List Sprague’s Pipit as Threatened 

or Endangered 

Notice of 90–day Petition Finding, Substantial 74 FR 63337-63343 

12/15/2009 90-Day Finding on Petitions To List 9 Species of Mussels From 

Texas as Threatened or Endangered With Critical Habitat 

Notice of 90–day Petition Finding, Substantial 74 FR 66260-66271 

12/16/2009 Partial 90-Day Finding on a Petition to List 475 Species in the 

Southwestern United States as Threatened or Endangered With 

Critical Habitat 

Notice of 90–day Petition Finding, Not 

Substantial & Substantial 

74 FR 66865-66905 

12/17/2009 12–month Finding on a Petition To Change the Final Listing of the 

Distinct Population Segment of the Canada Lynx To Include New 

Mexico 

Notice of 12–month 

Petition Finding, 

Warranted but Precluded 

74 FR 66937-66950 

01/05/2010 Listing Foreign Bird Species in Peru & Bolivia as Endangered 

Throughout Their Range 

Proposed Listing, Endangered 75 FR 605-649 


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TABLE 6. FY2010 COMPLETED LISTING ACTIONS—Continued 

Publication Date Title Actions FR Pages 

01/05/2010 Listing Six Foreign Birds as Endangered Throughout Their Range Proposed Listing, Endangered 75 FR 286-310 

01/05/2010 Withdrawal of Proposed Rule to List Cook’s Petrel Proposed rule, Withdrawal 75 FR 310-316 

01/05/2010 Final Rule to List the Galapagos Petrel & Heinroth’s Shearwater as 

Threatened Throughout Their Ranges 

Final Listing, Threatened 75 FR 235-250 

01/20/2010 Initiation of Status Review for Agave eggersiana & Solanum 

conocarpum 

Notice of Intent to 

Conduct Status Review 

75 FR 3190-3191 

02/09/2010 12–month Finding on a Petition to List the American Pika as 

Threatened or Endangered 

Notice of 12–month 

Petition Finding, Not 

Warranted 

75 FR 6437-6471 

02/25/2010 12-Month Finding on a Petition To List the Sonoran Desert 

Population of the Bald Eagle as a Threatened or Endangered Distinct Population Segment 

Notice of 12–month 

Petition Finding, Not 

Warranted 

75 FR 8601-8621 

02/25/2010 Withdrawal of Proposed Rule To List the Southwestern Washington/Columbia River Distinct Population Segment of Coastal 

Cutthroat Trout (Oncorhynchus clarki clarki) as Threatened 

Withdrawal of Proposed Rule to List 75 FR 8621-8644 

03/18/2010 90-Day Finding on a Petition to List the Berry Cave salamander as 

Endangered 

Notice of 90–day Petition Finding, Substantial 75 FR 13068-13071 

03/23/2010 90-Day Finding on a Petition to List the Southern Hickorynut Mussel (Obovaria jacksoniana) as Endangered or Threatened Notice of 90–day Petition Finding, Not 

Substantial 

75 FR 13717-13720 

03/23/2010 90-Day Finding on a Petition to List the Striped Newt as Threatened Notice of 90–day Petition Finding, Substantial 75 FR 13720-13726 

03/23/2010 12-Month Findings for Petitions to List the Greater Sage-Grouse 

(Centrocercus urophasianus) as Threatened or Endangered 

Notice of 12–month 

Petition Finding, 

Warranted but Precluded 

75 FR 13910-14014 

03/31/2010 12-Month Finding on a Petition to List the Tucson Shovel-Nosed 

Snake (Chionactis occipitalis klauberi) as Threatened or Endangered with Critical Habitat 

Notice of 12–month 

Petition Finding, 

Warranted but Precluded 

75 FR 16050-16065 

04/05/2010 90-Day Finding on a Petition To List Thorne’s Hairstreak Butterfly 

as or Endangered 

Notice of 90–day Petition Finding, Substantial 75 FR 17062-17070 

04/06/2010 12–month Finding on a Petition To List the Mountain Whitefish in 

the Big Lost River, Idaho, as Endangered or Threatened 

Notice of 12–month 

Petition Finding, Not 

Warranted 

75 FR 17352-17363 

04/06/2010 90-Day Finding on a Petition to List a Stonefly (Isoperla jewetti) & a 

Mayfly (Fallceon eatoni) as Threatened or Endangered with Critical Habitat 

Notice of 90–day Petition Finding, Not 

Substantial 

75 FR 17363-17367 

04/07/2010 12-Month Finding on a Petition to Reclassify the Delta Smelt From 

Threatened to Endangered Throughout Its Range 

Notice of 12–month 

Petition Finding, 

Warranted but Precluded 

75 FR 17667-17680 

04/13/2010 Determination of Endangered Status for 48 Species on Kauai & 

Designation of Critical Habitat 

Final Listing, Endangered 75 FR 18959-19165 

04/15/2010 Initiation of Status Review of the North American Wolverine in the 

Contiguous United States 

Notice of Initiation of 

Status Review 

75 FR 19591-19592 


srobinson on DSKHWCL6B1PROD with PROPOSALS2
54748 Federal Register / Vol. 75, No. 173 / Wednesday, September 8, 2010 / Proposed Rules 

TABLE 6. FY2010 COMPLETED LISTING ACTIONS—Continued 

Publication Date Title Actions FR Pages 

04/15/2010 12-Month Finding on a Petition to List the Wyoming Pocket Gopher 

as Endangered or Threatened with Critical Habitat 

Notice of 12–month 

Petition Finding, Not 

Warranted 

75 FR 19592-19607 

04/16/2010 90-Day Finding on a Petition to List a Distinct Population Segment 

of the Fisher in Its United States Northern Rocky Mountain 

Range as Endangered or Threatened with Critical Habitat 

Notice of 90–day Petition Finding, 

Substantial 

75 FR 19925-19935 

04/20/2010 Initiation of Status Review for Sacramento splittail (Pogonichthys 

macrolepidotus) 

Notice of Initiation of 

Status Review 

75 FR 20547-20548 

04/26/2010 90-Day Finding on a Petition to List the Harlequin Butterfly as Endangered Notice of 90–day Petition Finding, 

Substantial 

75 FR 21568-21571 

04/27/2010 12-Month Finding on a Petition to List Susan’s Purse-making 

Caddisfly (Ochrotrichia susanae) as Threatened or Endangered 

Notice of 12–month 

Petition Finding, Not 

Warranted 

75 FR 22012-22025 

04/27/2010 90–day Finding on a Petition to List the Mohave Ground Squirrel 

as Endangered with Critical Habitat 

Notice of 90–day Petition Finding, Substantial 75 FR 22063-22070 

05/04/2010 90-Day Finding on a Petition to List Hermes Copper Butterfly as 

Threatened or Endangered 

Notice of 90–day Petition Finding, Substantial 75 FR 23654-23663 

6/1/2010 90-Day Finding on a Petition To List Castanea pumila var. 

ozarkensis 

Notice of 90–day Petition Finding, Substantial 75 FR 30313-30318 

6/1/2010 12–month Finding on a Petition to List the White-tailed Prairie Dog 

as Endangered or Threatened 

Notice of 12–month 

petition finding, Not 

warranted 

75 FR 30338-30363 

6/9/2010 90-Day Finding on a Petition To List van Rossem’s Gull-billed Tern 

as Endangered orThreatened. 

Notice of 90–day Petition Finding, Substantial 75 FR 32728-32734 

6/16/2010 90-Day Finding on Five Petitions to List Seven Species of Hawaiian Yellow-faced Bees as Endangered Notice of 90–day Petition Finding, Substantial 75 FR 34077-34088 

6/22/2010 12-Month Finding on a Petition to List the Least Chub as Threatened or Endangered Notice of 12–month 

petition finding, 

Warranted but precluded 

75 FR 35398-35424 

6/23/2010 90-Day Finding on a Petition to List the Honduran Emerald Hummingbird as Endangered Notice of 90–day Petition Finding, Substantial 75 FR 35746-35751 

6/23/2010 Listing Ipomopsis polyantha (Pagosa Skyrocket) as Endangered 

Throughout Its Range, and Listing Penstemon debilis (Parachute 

Beardtongue) and Phacelia submutica (DeBeque Phacelia) as 

Threatened Throughout Their Range 

Proposed Listing Endangered Proposed 

Listing Threatened 

75 FR 35721-35746 

6/24/2010 Listing the Flying Earwig Hawaiian Damselfly and Pacific Hawaiian 

Damselfly As Endangered Throughout Their Ranges 

Final Listing Endangered 75 FR 35990-36012 

6/24/2010 Listing the Cumberland Darter, Rush Darter, Yellowcheek Darter, 

Chucky Madtom, and Laurel Dace as Endangered Throughout 

Their Ranges 

Proposed Listing Endangered 75 FR 36035-36057 

6/29/2010 Listing the Mountain Plover as Threatened Reinstatement of Proposed Listing 

Threatened 

75 FR 37353-37358 

7/20/2010 90-Day Finding on a Petition to List Pinus albicaulis (Whitebark 

Pine) as Endangered or Threatened with Critical Habitat 

Notice of 90–day Petition Finding, Substantial 75 FR 42033-42040 


srobinson on DSKHWCL6B1PROD with PROPOSALS2
Federal Register / Vol. 75, No. 173 / Wednesday, September 8, 2010 / Proposed Rules 54749 

TABLE 6. FY2010 COMPLETED LISTING ACTIONS—Continued 

Publication Date Title Actions FR Pages 

7/20/2010 12-Month Finding on a Petition to List the Amargosa Toad as 

Threatened or Endangered 

Notice of 12–month 

petition finding, Not 

warranted 

75 FR 42040-42054 

7/20/2010 90-Day Finding on a Petition to List the Giant Palouse Earthworm 

(Driloleirus americanus) as Threatened or Endangered 

Notice of 90–day Petition Finding, Substantial 75 FR 42059-42066 

7/27/2010 Determination on Listing the Black-Breasted Puffleg as Endangered 

Throughout its Range; Final Rule 

Final Listing Endangered 75 FR 43844-43853 

7/27/2010 Final Rule to List the Medium Tree-Finch (Camarhynchus pauper) 

as Endangered Throughout Its Range 

Final Listing Endangered 75 FR 43853-43864 

8/3/2010 Determination of Threatened Status for Five Penguin Species Final Listing Threatened 75 FR 45497- 45527 

8/4/2010 90-Day Finding on a Petition To List the Mexican Gray Wolf as an 

Endangered Subspecies With Critical Habitat 

Notice of 90–day Petition Finding, Substantial 75 FR 46894- 46898 

8/10/2010 90-Day Finding on a Petition to List Arctostaphylos franciscana as 

Endangered with Critical Habitat 

Notice of 90–day Petition Finding, Substantial 75 FR 48294-48298 

8/17/2010 Listing Three Foreign Bird Species from Latin America and the 

Caribbean as Endangered Throughout Their Range 

Final Listing Endangered 75 FR 50813-50842 

8/17/2010 90-Day Finding on a Petition to List Brian Head Mountainsnail as 

Endangered or Threatened with Critical Habitat 

Notice of 90–day Petition Finding, Not 

substantial 

75 FR 50739-50742 

8/24/2010 90-Day Finding on a Petition to List the Oklahoma Grass Pink Orchid as Endangered or Threatened Notice of 90–day Petition Finding, Substantial 75 FR 51969-51974 

Our expeditious progress also 

includes work on listing actions that we 

funded in FY 2010 but have not yet 

been completed to date (Table 7). These 

actions are listed below. Actions in the 

top section of the table are being 

conducted under a deadline set by a 

court. Actions in the middle section of 

the table are being conducted to meet 

statutory timelines, that is, timelines 

required under the ESA. Actions in the 

bottom section of the table are highpriority listing actions. These actions 

include work primarily on species with 

an LPN of 2, and selection of these 

species is partially based on available 

staff resources, and when appropriate, 

include species with a lower priority if 

they overlap geographically or have the 

same threats as the species with the 

high priority. Including these species 

together in the same proposed rule 

results in considerable savings in time 

and funding, as compared to preparing 

separate proposed rules for each of them 

in the future. 

TABLE 7. ACTIONS FUNDED IN FY 2010 BUT NOT YET COMPLETED

Species Action 

Actions Subject to Court Order/Settlement Agreement 

6 Birds from Eurasia Final listing determination 

African penguin Final listing determination 

Flat-tailed horned lizard Final listing determination 

Mountain plover4 Final listing determination 

6 Birds from Peru Proposed listing determination 

Sacramento splittail 12–month petition finding 

Pacific walrus 12–month petition finding 

Gunnison sage-grouse 12–month petition finding 

Wolverine 12–month petition finding 


srobinson on DSKHWCL6B1PROD with PROPOSALS2
54750 Federal Register / Vol. 75, No. 173 / Wednesday, September 8, 2010 / Proposed Rules 

TABLE 7. ACTIONS FUNDED IN FY 2010 BUT NOT YET COMPLETED—Continued 

Species Action 

Arctic grayling 12–month petition finding 

Agave eggergsiana 12–month petition finding 

Solanum conocarpum 12–month petition finding 

Jemez Mountains salamander 12–month petition finding 

Sprague’s pipit 12–month petition finding 

Desert tortoise – Sonoran population 12–month petition finding 

Pygmy rabbit (rangewide)1 12–month petition finding 

Thorne’s Hairstreak butterfly4 12–month petition finding 

Hermes copper butterfly4 12–month petition finding 

Actions with Statutory Deadlines 

Casey’s june beetle Final listing determination 

Georgia pigtoe, interrupted rocksnail, and rough hornsnail Final listing determination 

7 Bird species from Brazil Final listing determination 

Southern rockhopper penguin – Campbell Plateau population Final listing determination 

5 Bird species from Colombia and Ecuador Final listing determination 

Queen Charlotte goshawk Final listing determination 

5 species southeast fish (Cumberland Darter, Rush Darter, 

Yellowcheek Darter, Chucky Madtom, and Laurel Dace) 

Final listing determination 

Salmon crested cockatoo Proposed listing determination 

CA golden trout 12–month petition finding 

Black-footed albatross 12–month petition finding 

Mount Charleston blue butterfly 12–month petition finding 

Mojave fringe-toed lizard1 12–month petition finding 

Kokanee – Lake Sammamish population1 12–month petition finding 

Cactus ferruginous pygmy-owl1 12–month petition finding 

Northern leopard frog 12–month petition finding 

Tehachapi slender salamander 12–month petition finding 

Coqui Llanero 12–month petition finding 

Dusky tree vole 12–month petition finding 

3 MT invertebrates (mist forestfly(Lednia tumana), Oreohelix sp.3, 

Oreohelix sp. 31) from 206 species petition 

12–month petition finding 

5 UT plants (Astragalus hamiltonii, Eriogonum soredium, Lepidium 

ostleri, Penstemon flowersii, Trifolium friscanum) from 206 species 

petition 

12–month petition finding 

2 CO plants (Astragalus microcymbus, Astragalus schmolliae) from 

206 species petition 

12–month petition finding 

5 WY plants (Abronia ammophila, Agrostis rossiae, Astragalus 

proimanthus, Boechere (Arabis) pusilla, Penstemon gibbensii) from 

206 species petition 

12–month petition finding 

Leatherside chub (from 206 species petition) 12–month petition finding 


srobinson on DSKHWCL6B1PROD with PROPOSALS2
Federal Register / Vol. 75, No. 173 / Wednesday, September 8, 2010 / Proposed Rules 54751 

TABLE 7. ACTIONS FUNDED IN FY 2010 BUT NOT YET COMPLETED—Continued 

Species Action 

Frigid ambersnail (from 206 species petition) 12–month petition finding 

Gopher tortoise – eastern population 12–month petition finding 

Wrights marsh thistle 12–month petition finding 

67 of 475 southwest species 12–month petition finding 

Grand Canyon scorpion (from 475 species petition) 12–month petition finding 

Anacroneuria wipukupa (a stonefly from 475 species petition) 12–month petition finding 

Rattlesnake-master borer moth (from 475 species petition) 12–month petition finding 

3 Texas moths (Ursia furtiva, Sphingicampa blanchardi, Agapema 

galbina) (from 475 species petition) 

12–month petition finding 

2 Texas shiners (Cyprinella sp., Cyprinella lepida) (from 475 species 

petition) 

12–month petition finding 

3 South Arizona plants (Erigeron piscaticus, Astragalus hypoxylus, 

Amoreuxia gonzalezii) (from 475 species petition) 

12–month petition finding 

5 Central Texas mussel species (3 from 474 species petition) 12–month petition finding 

14 parrots (foreign species) 12–month petition finding 

Berry Cave salamander1 12–month petition finding 

Striped Newt1 12–month petition finding 

Fisher – Northern Rocky Mountain Range1 12–month petition finding 

Mohave Ground Squirrel1 12–month petition finding 

Puerto Rico Harlequin Butterfly 12–month petition finding 

Western gull-billed tern 12–month petition finding 

Ozark chinquapin (Castanea pumila var. ozarkensis) 12–month petition finding 

HI yellow-faced bees 12–month petition finding 

Giant Palouse earthworm 12–month petition finding 

Whitebark pine 12–month petition finding 

OK grass pink (Calopogon oklahomensis)1 12–month petition finding 

Southeastern pop snowy plover & wintering pop. of piping plover1 90–day petition finding 

Eagle Lake trout1 90–day petition finding 

Smooth-billed ani1 90–day petition finding 

Bay Springs salamander1 90–day petition finding 

32 species of snails and slugs1 90–day petition finding 

42 snail species (Nevada & Utah) 90–day petition finding 

Red knot roselaari subspecies 90–day petition finding 

Peary caribou 90–day petition finding 

Plains bison 90–day petition finding 

Spring Mountains checkerspot butterfly 90–day petition finding 

Spring pygmy sunfish 90–day petition finding 

Bay skipper 90–day petition finding 


srobinson on DSKHWCL6B1PROD with PROPOSALS2
54752 Federal Register / Vol. 75, No. 173 / Wednesday, September 8, 2010 / Proposed Rules 

TABLE 7. ACTIONS FUNDED IN FY 2010 BUT NOT YET COMPLETED—Continued 

Species Action 

Unsilvered fritillary 90–day petition finding 

Texas kangaroo rat 90–day petition finding 

Spot-tailed earless lizard 90–day petition finding 

Eastern small-footed bat 90–day petition finding 

Northern long-eared bat 90–day petition finding 

Prairie chub 90–day petition finding 

10 species of Great Basin butterfly 90–day petition finding 

6 sand dune (scarab) beetles 90–day petition finding 

Golden-winged warbler 90–day petition finding 

Sand-verbena moth 90–day petition finding 

404 Southeast species 90–day petition finding 

High Priority Listing Actions3

19 Oahu candidate species3 (16 plants, 3 damselflies) (15 with LPN = 

2, 3 with LPN = 3, 1 with LPN =9) 

Proposed listing 

19 Maui-Nui candidate species3 (16 plants, 3 tree snails) (14 with 

LPN = 2, 2 with LPN = 3, 3 with LPN = 8) 

Proposed listing 

Dune sagebrush lizard (formerly Sand dune lizard)3 (LPN = 2) Proposed listing 

2 Arizona springsnails3 (Pyrgulopsis bernadina (LPN = 2), Pyrgulopsis 

trivialis (LPN = 2)) 

Proposed listing 

New Mexico springsnail3 (Pyrgulopsis chupaderae (LPN = 2) Proposed listing 

2 mussels3 (rayed bean (LPN = 2), snuffbox No LPN) Proposed listing 

2 mussels3 (sheepnose (LPN = 2), spectaclecase (LPN = 4),) Proposed listing 

Ozark hellbender2 (LPN = 3) Proposed listing 

Altamaha spinymussel3 (LPN = 2) Proposed listing 

8 southeast mussels (southern kidneyshell (LPN = 2), round 

ebonyshell (LPN = 2), Alabama pearlshell (LPN = 2), southern 

sandshell (LPN = 5), fuzzy pigtoe (LPN = 5), Choctaw bean (LPN = 

5), narrow pigtoe (LPN = 5), and tapered pigtoe (LPN = 11)) 

Proposed listing 

1 Funds for listing actions for these species were provided in previous FYs. 2 We funded a proposed rule for this subspecies with an LPN of 3 ahead of other species with LPN of 2, because the threats to the species 

were so imminent and of a high magnitude that we considered emergency listing if we were unable to fund work on a proposed listing rule in FY 

2008. 3 Although funds for these high-priority listing actions were provided in FY 2008 or 2009, due to the complexity of these actions and competing 

priorities, these actions are still being developed. 4Partially funded with FY 2010 funds; also will be funded with FY 2011 funds. 

We have endeavored to make our 

listing actions as efficient and timely as 

possible, given the requirements of the 

relevant law and regulations, and 

constraints relating to workload and 

personnel. We are continually 

considering ways to streamline 

processes or achieve economies of scale, 

such as by batching related actions 

together. Given our limited budget for 

implementing section 4 of the ESA, 

these actions described above 

collectively constitute expeditious 

progress. 

The upper Missouri River DPS of 

Arctic grayling will be added to the list 

of candidate species upon publication of 

this 12–month finding. We will 

continue to monitor the status of this 

species as new information becomes 

available. This review will determine if 

a change in status is warranted, 

including the need to make prompt use 

of emergency listing procedures. 

We intend that any proposed listing 

action for the upper Missouri River DPS 

of Arctic grayling will be as accurate as 

possible. Therefore, we will continue to 

accept additional information and 

comments from all concerned 

governmental agencies, the scientific 

community, industry, or any other 

interested party concerning this finding. 

References Cited 

A complete list of references cited is 

available on the Internet at http:// 


srobinson on DSKHWCL6B1PROD with PROPOSALS2
Federal Register / Vol. 75, No. 173 / Wednesday, September 8, 2010 / Proposed Rules 54753 

www.regulations.gov and upon request 

from the Montana Field Office (see 

ADDRESSES section). 

Authors 

The primary authors of this notice are 

the staff members of the Montana Field 

Office. 

Authority 

The authority for this action is section 

4 of the Endangered Species Act of 

1973, as amended (16 U.S.C. 1531 et 

seq.). 

Dated: August 30, 2010 

Daniel M. Ashe, 

Acting Director, Fish and Wildlife Service. 

[FR Doc. 2010–22038 Filed 9–7–10; 8:45 am] 

BILLING CODE 4310–55–S 


srobinson on DSKHWCL6B1PROD with PROPOSALS2