[Federal Register Volume 72, Number 78 (Tuesday, April 24, 2007)]
[Proposed Rules]
[Pages 20305-20314]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: E7-7484]


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DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17


Endangered and Threatened Wildlife and Plants; Revised 12-Month 
Finding for Upper Missouri River Distinct Population Segment of Fluvial 
Arctic Grayling

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Notice of revised 12-month finding.

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SUMMARY: We, the Fish and Wildlife Service (Service), announce our 
revised 12-month finding on a petition to list the upper Missouri River 
Distinct Population Segment (DPS) of fluvial Arctic grayling (Thymallus 
arcticus) as threatened or endangered under the Endangered Species Act 
of 1973, as amended (Act). After a review of the best available 
scientific and commercial information, we find that fluvial Arctic 
grayling of the upper Missouri River does not constitute a species, 
subspecies, or distinct population segment under the Act. Therefore, we 
find that the petition to list the upper Missouri River DPS of fluvial 
Arctic grayling is not warranted, and we withdraw the fluvial Arctic 
grayling from the candidate list. The Service continues to seek new 
information on the taxonomy, biology, ecology, and status of fluvial 
Arctic grayling and to support cooperative conservation of fluvial 
Arctic grayling in the upper Missouri River system.

DATES: This finding was made on April 24, 2007.

ADDRESSES: The complete file for this finding is available for 
inspection, by appointment, during normal business hours, at the U.S. 
Fish and Wildlife Service, Montana Field Office, 585 Shepard Way, 
Helena, MT 59601; telephone (406) 449-5225. Submit new information, 
materials, comments, or questions concerning this species to us at this 
address (Attention: Arctic grayling).

FOR FURTHER INFORMATION CONTACT: Mark Wilson, Field Supervisor, Montana 
Field Office, at the address and telephone listed above.

SUPPLEMENTARY INFORMATION:

Species Information

Description

    The Arctic grayling (Thymallus arcticus) belongs to the family 
Salmonidae (salmon, trout, charr, whitefishes), subfamily Thymallinae 
(graylings), and is represented by a single genus, Thymallus, which 
contains three other recognized species in addition to T. arcticus 
(Scott and Crossman 1973, pp. 301-302; Behnke 2002, pp. 327-331). 
Arctic grayling have elongate, laterally compressed bodies with deeply 
forked tails, and adults typically average 254 to 330 millimeters (10 
to 13 inches) in length. Coloration varies from silvery or iridescent 
blue and lavender, to dark blue (Behnke 2002, pp. 327-328). 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. Dark spots are often evident on the body towards 
the head (Behnke 2002, pp. 327-328).

[[Page 20306]]

Distribution

    Arctic grayling have a primarily holarctic distribution and are 
native to Arctic Ocean drainages of northwestern Canada and Alaska, 
from the Peace, Saskatchewan, and Athabasca River drainages in Alberta 
eastward to Hudson Bay and westward to the Bering Straits and eastern 
Siberia and northern Eurasia (Scott and Crossman 1973, pp. 301-302). 
Arctic grayling also are native to Pacific coast drainages of Alaska 
and Canada as far south as the Stikine River in British Columbia (Scott 
and Crossman 1973, pp. 301-302; Nelson and Paetz 1991, pp. 253-256; 
Behnke 2002, pp. 327-331). Arctic grayling generally occur throughout 
their native range though the species is extirpated in some locations 
(Michigan) and has experienced local range contraction in others (e.g., 
Peace-Willison watershed in British Columbia (Blackman et al. (1990, 
pp. 15, 17, 34), portions of Alberta (Alberta Sustainable Resource 
Development (2005; pp. iv, 5-18), and Montana).
    In North America, two populations of Arctic grayling, believed to 
have been isolated by Pleistocene glaciations, have been recorded 
outside of Canada and Alaska (Vincent 1962, pp. 23-31). One population 
was found in streams and rivers of the Great Lakes region of northern 
Michigan, but those grayling were extirpated in the 1930s (Hubbs and 
Lagler 1949, p. 44; Scott and Crossman 1973, p. 301). The second 
population historically inhabited watersheds in the upper Missouri 
River basin upstream of Great Falls, Montana (Figure 1).
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    Genetic data indicate Arctic grayling native to the Missouri River 
system were most likely isolated geographically from Hudson Bay and 
Arctic Ocean drainages by the onset of Wisconsin glaciation 
approximately 70,000 years ago (Redenbach and Taylor 1999, p. 32). 
Arctic grayling native to the upper Missouri River system are 
genetically diverged from Arctic grayling in the northern part of the 
species' range (Lynch and Vyse 1979, pp. 268-270, 275; Everett 1986, 
pp. 15-16, 79-80; Redenbach and Taylor 1999, pp. 23, 28-29, 32-33; 
reviewed by Leary 2005, pp. 1-3; reviewed by Campton 2006, pp. 5-6), 
and appear to be most closely related evolutionarily to populations in 
the Fond du Lac area of northeastern Saskatchewan, Canada (Stamford and 
Taylor 2004, p. 1538). Genetic divergence happens when two or more 
genetic characteristics that have occurred naturally over time are 
passed from one generation to subsequent generations. Arctic grayling 
in the upper Missouri River basin are commonly referred to as ``Montana 
grayling'' and have been variously categorized as a separate species 
(Thymallus montanas; Scott and Crossman 1973, p. 301) or subspecies (T. 
arcticus montanus; Williams et al. 1989, p. 4), but these designations 
are of uncertain validity (Scott and Crossman 1973, p. 301) and not 
widely accepted (Kaya 1990, pp. 3-4; Integrated Taxonomic Information 
System 2006). The lack of accepted subspecific designations is based on 
morphological similarity among disjunct populations (Kaya 1990, p. 4).
    Arctic grayling in the upper Missouri River basin currently 
represent the southern extent of the species' range (Scott and Crossman 
1973, pp. 301-302), and both migratory, river-dwelling (fluvial) and 
lake-dwelling (adfluvial and lacustrine) populations are native to the 
upper Missouri River. For simplicity, the term ``adfluvial'' will be 
used to refer to all Arctic grayling populations associated with lakes 
or reservoirs. The migratory, stream- and river-dwelling form of Arctic 
grayling native to the upper Missouri River is hereafter referred to as 
``fluvial'' Arctic grayling of the upper Missouri River.

Arctic Grayling Distribution in the Upper Missouri River Basin

    Fluvial Arctic grayling reside in the Big Hole River and the lower 
reaches of connected tributaries (see Figure 1 above). Adfluvial Arctic 
grayling native to the upper Missouri River system are known to reside 
in the Red Rock Lakes system, in the upper reaches of the Beaverhead 
River within the Centennial Valley, Montana (Vincent 1962, p. 120; see 
Figure 1 above). An indigenous Arctic grayling population exhibiting 
adfluvial characteristics also is present in the Madison River upstream 
from Ennis Reservoir (see Figure 1 above). The adfluvial 
characteristics expressed by the Madison River-Ennis Reservoir 
population may reflect recent divergence away from the presumed 
ancestral fluvial form resulting from the construction of Ennis Dam 
(Kaya 1990, p. 33; Kaya 1992a, p. 53). A few adfluvial populations 
found in small lakes within the Big Hole River system (in particular 
Miner and Mussigbrod Lakes; see Figure 1 above) may be remnant native 
populations derived from fluvial Arctic grayling from the Big Hole 
River and isolated by recent habitat fragmentation, but widespread 
stocking of these and other locations with hatchery-reared Arctic 
grayling during the 1930s-1950s (e.g., Everett 1986, p. 4, 16; Kaya 
1990, pp. 31, 75-80) also makes it possible that these fish are 
introduced populations or that the existing populations are a mixture 
of native and introduced Arctic grayling.

Ecology

    Northcote (1995) and Kaya (1990) reviewed the ecology of Arctic 
grayling and fluvial Arctic grayling of the upper Missouri River, 
respectively. Much of the information on fluvial Arctic grayling in the 
upper Missouri River system comes from the Big Hole River, Montana (see 
Figure 1 above), which contains a fluvial population. Arctic grayling 
exhibit life history and migratory forms present in other species of 
inland trout and charr, including fluvial and adfluvial. Fluvial 
populations are characterized by a cycle of migratory behavior over 
their lifespan between spawning, feeding, and overwintering habitats 
within rivers or streams (Northcote 1995, pp. 156-160). Fluvial Arctic 
grayling typically migrate upstream to spawn in tributary or mainstem 
river locations and downstream to overwintering habitats. Such movement 
patterns have been observed in fluvial Arctic grayling in Big Hole 
River, Montana (Shepard and Oswald 1989, pp. 18, 27-28). Migrations to 
feeding habitats may occur if these locations differ from spawning or 
overwintering habitats (Kaya 1990, pp. 9-11). Overall, movements by 
fluvial populations within and among tributaries and mainstem rivers 
may cover hundreds of kilometers (Armstrong 1986, p. 7). Fluvial Arctic 
grayling in the Big Hole River system have been shown to migrate in 
excess of 80 km (50 mi) between spawning, feeding and wintering areas 
(Shepard and Oswald 1989, pp. 18, 21; Lamothe and Magee 2003, pp. 7, 
11, 17). Adfluvial Arctic grayling feed and overwinter in lakes, but 
migrate to inlet or outlet streams to spawn (Northcote 1995, p. 148-
149; Northcote 1997, pp. 1030-1034).
    Age at maturity and longevity in Arctic grayling varies among 
systems and is probably related to growth rate, with populations in 
colder, less productive habitats maturing at later ages and having a 
greater lifespan (Northcote 1995, pp. 155-157). Fluvial Arctic grayling 
in the Big Hole River system typically mature at 2 years of age (males) 
or 3 years of age (females), and individuals older than 6 years of age 
are rare (Liknes 1981, pp. 16-18; Kaya 1990, pp. 18-20; Magee and 
Lamothe 2003, p. 22). Arctic grayling are spring spawners. In Montana, 
Arctic grayling typically spawn from late April to mid-May by 
depositing adhesive eggs over gravel substrate without excavating a 
nest or redd (Shepard and Oswald 1989, pp. 24-25, 29; Kaya 1990, pp. 
15-16). In general, the reproductive ecology of Arctic grayling is 
somewhat different from other salmonid species (trout and salmon) in 
that Arctic grayling eggs tend to be comparatively small (Behnke 2002, 
p. 328), and males establish and defend spawning territories rather 
than defending access to females (Northcote 1995, p. 150). The time 
required for development of eggs from embryo until they emerge from 
stream gravel and become swim-up fry varies with water temperature, but 
averages about 3 weeks for Arctic grayling in the upper Missouri River 
basin (Kaya 1990, pp. 16-17). Small, weakly swimming fry of fluvial 
Arctic grayling prefer low velocity stream habitats (Kaya 1990, pp. 23-
24; Northcote 1995, pp. 152-153).
    Arctic grayling of all ages feed primarily on aquatic and 
terrestrial invertebrates captured on or near the water surface 
(Northcote 1995, pp. 153-154; Behnke 2002, p. 328). They also will feed 
opportunistically on fish and fish eggs (Northcote 1995, p. 154; Behnke 
2002, p. 328). Feeding locations for individual fish are typically 
established and maintained through size-mediated dominance hierarchies 
(e.g., Hughes 1992, pp. 1994-1995).
    Although fluvial Arctic grayling may have specific habitat 
requirements depending on their life stage (e.g., fry) and ecological 
activity (e.g., spawning), individuals inhabiting streams and rivers 
often exhibit a preference for pool habitats (Liknes 1981, pp. 22, 28; 
Kaya 1990, pp. 20-21; Lamothe and Magee 2003, pp. 13-14, 17; Lamothe 
and Magee 2004, p. 24). Vincent (1962, pp. 39, 42) concluded that 
fluvial Arctic grayling in Montana typically reside in

[[Page 20309]]

streams with low-to-moderate gradient (<4 percent) and prefer low-to-
moderate water velocities (<60 centimeters/sec). Observations of 
fluvial Arctic grayling habitat use in the Big Hole River by Liknes 
(1981, p. 28) and Liknes and Gould (1987, p. 128) are consistent with 
these generalizations.
    Arctic grayling generally prefer cool or coldwater habitats (Hubert 
et al. 1985, pp. 9, 14, 25, 27). Selong et al. (2001, p. 1032) placed 
Arctic grayling in a ``coldwater'' group of salmonids, along with 
Arctic charr and bull trout, based on critical thermal maximum values.

Genetic Relationships Among Arctic Grayling Populations in the Upper 
Missouri River Basin

    Discussion of genetic divergence among Arctic grayling populations 
is complicated by the extensive hatchery propagation and 
transplantation of stocks from location to location (Everett 1986, p. 
40). Over 10 million grayling of unknown origin were stocked in the Big 
Hole River over a 30-year period from the 1930s to the 1950s (Kaya 
1990, pp. 31, 75-80). Everett (1986 pp. 42, 43, 47) concluded that the 
effect of grayling introductions on local genetics appears stronger in 
lake populations than in the Big Hole River. Nonetheless, the limited 
available genetic data suggest the presence of two or more groups--
clusters or sets of populations that are genetically more closely 
related to each other than they are to other populations of the same 
species--of Arctic grayling within the upper Missouri River that may 
not be strictly delineated by geography and life history (Leary 2005, 
p. 3; Campton 2006, pp. 6-9, 12).
    Inferences about genetic differences among Arctic grayling 
populations within the upper Missouri River basin are primarily based 
on data collected by Everett (1986) and Leary (1990). These two studies 
examined how a particular form (allele) of a protein molecule 
(allozyme) varied in frequency across Arctic grayling populations in 
Montana. Allozymes are gene products coded by DNA, so allozyme 
variation can be used to infer genetic relationships among populations, 
subspecies or species. Campton (2006, pp. 6, 12), in his review of 
those data, suggested the existence of two possible genetic groups: (a) 
A Big Hole-Madison River group that includes the fluvial population in 
the Big Hole River, certain populations in adjoining waters of the Big 
Hole River system (e.g., Bobcat, Miner, and Mussigbrod Lakes, and Steel 
Creek; see Figure 1 above; see Everett 1986, p. 7; Leary 1990, pp. 6-
8), and fish from the Madison River-Ennis Reservoir; and (b) a Red Rock 
Lakes group that includes native adfluvial populations from the Red 
Rock and Elk Lakes system in the upper Beaverhead River system, and a 
number of introduced adfluvial populations (Agnes, Grebe, Rogers, 
Odell, and Elizabeth Lakes; see Leary 1990, pp. 7-8) believed to be 
derived from human introductions of Red Rock Lakes grayling and/or 
associated hatchery stocks. The two groups (Big Hole-Madison and Red 
Rock Lakes) are differentiated by divergent allele frequencies for two 
allozymes (Campton 2006, p. 6). The relative genetic difference between 
these two groups within the upper Missouri River basin is less than the 
difference between upper Missouri River Arctic grayling and sample 
populations from Alaska and Canada (Everett 1986, p. 80; Leary 1990, 
pp. 1, 7-8). The level of genetic divergence observed among populations 
within the upper Missouri River is consistent with what would be 
expected for populations within a geographic area that share a recent 
ancestry but have since diverged, as compared with the greater 
divergence observed among populations from different geographic areas 
or river systems that have been separated from each other for a much 
longer period of time (i.e., upper Missouri River versus Alaskan and 
Canadian populations).
    Campton (2006, p. 12) also noted that a few adfluvial populations 
of Arctic grayling in the Big Hole River drainage, including Miner Lake 
(see Figure 1 above), appear to share recent ancestry with the mainstem 
Big Hole River fluvial population.
    Like Campton, Leary also concluded that Big Hole River and Madison 
River grayling samples appear to be quite similar (Leary 2005, p. 3). 
Leary's interpretation of the genetic relationships among Miner Lake, 
Red Rock Lakes, and Elk Lake populations was different from Campton's. 
Leary found Miner Lake to be very divergent from all the others, but 
also concluded that there was significant divergence between the Red 
Rock Lakes and Elk Lake samples (Leary 2005, p. 3). He interpreted the 
allozyme data to mean that the adfluvial samples do not appear to form 
a genetically distinct group and consequently concluded that the data 
do not support the premise that the fluvial and adfluvial life 
histories fall into two distinct genetic lineages (Leary 2005, p. 3). 
Rather, he contended the data represent divergence among populations 
regardless of life history (Leary 2005, p. 3). In his review, Campton 
(2006) concurred that the apparent genetic divergence between the two 
groups (Big Hole-Madison River and Red Rock Lakes) was not completely 
consistent with life histories because several adfluvial populations 
belonged to the Big Hole River-Madison River genetic group.
    An Arctic grayling population residing in the Sunnyslope irrigation 
canal in Teton County, Montana, is thought to be derived from an 
introduction into Pishkin Reservoir (Kaya 1990, p. 41; see Figure 1 
above) and is not easily assigned to either of the two genetic groups 
suggested by Campton. These fish appear to be genetic outliers relative 
to the two other native genetic groups of Arctic grayling (Leary 1990, 
p. 8; Campton 2006, p. 7).
    Overall, both Campton and Leary observe that: (a) Fluvial Arctic 
grayling from the Big Hole River are genetically different from native 
adfluvial Arctic grayling in Red Rock Lakes based on observed 
differences in allozyme allele frequencies even if the genetic 
divergence between these populations appears to be low (average Nei's 
genetic distance of the cluster containing these populations equals 
0.0132 (Leary 1990, pp. 1,8)); (b) the existing genetic data do not 
strongly support the hypothesis that the fluvial form of Arctic 
grayling in the upper Missouri River represents a unique genetic 
lineage, because it is genetically similar to adfluvial populations in 
Miner Lake and in the Madison River (Leary 2005, pp. 3-4; Campton 2006, 
p. 12); and (c) the low allozyme variability in upper Missouri River 
Arctic grayling samples results in a weak dataset for resolving 
ancestries among recently diverged populations (Leary 2005, pp. 3-4; 
Campton 2006, p. 10). The Service views Campton's and Leary's 
conclusions about the ancestral relationships among Arctic grayling 
populations in the upper Missouri River as tentative, given the 
inherent limitations of the existing genetic data. However, it is the 
best available scientific information at this time. Further 
investigations with more variable genetic markers, such as 
microsatellite DNA, may clarify genetic relationships (Campton 2006, 
pp. 10, 14).

Heritable, Behavioral Differences Between Fluvial and Adfluvial Arctic 
Grayling in the Upper Missouri River Basin

    Arctic grayling exhibit at least two life histories in the upper 
Missouri River system--a river-dwelling fluvial form and a lake-
dwelling adfluvial form. Life history variation in salmonid fishes 
(trout and salmon) may or may not be related to genetic differentiation 
(e.g., Fausch and Young 1995, p. 365). However, experiments designed to 
determine whether behavioral

[[Page 20310]]

differences were due to genetic or environmental influences found that 
the behavioral differences between fluvial and adfluvial Arctic 
grayling in Montana were heritable. In tests of swimming behavior of 
young-of-year Arctic grayling raised in common conditions in captivity, 
progeny of fluvial Big Hole River fish behaved significantly 
differently, on average, than adfluvial progeny from Red Rock Lakes and 
Madison River-Ennis Reservoir populations (Kaya 1989, 1991; Kaya and 
Jeanes 1995). The Big Hole River progeny exhibited a greater tendency 
to hold position in flowing water (Kaya and Jeanes 1995, pp. 453-456). 
Because the test fish from the Big Hole River population were progeny 
of parents reared in a non-fluvial environment, retention of this 
rheotactic behavior (behavior in response to flowing water) was taken 
as evidence that such behavior has a genetic (heritable) basis (Kaya 
and Jeanes 1995, p. 456), consistent with conclusions of previous 
investigations (Kaya 1989, pp. 474, 478-479; Kaya 1991, pp. 53, 55-58).
    Expression of rheotactic characteristics in Arctic grayling also 
can be influenced by ontogeny, or the developmental history of an 
individual (in this case, time from emergence from gravel as fry until 
maturity; Kaya 1991, pp. 53, 55-57), and environmental conditions, such 
as time of day (Kaya 1989, p. 56), light intensity (Kaya 1989, p. 478; 
Kaya 1991, p. 56), or water temperature (Kaya 1989, p. 478). However, 
the collective results are nonetheless consistent with the hypothesis 
that heritable, behavioral differences in the test populations exist 
between the fluvial and adfluvial populations and those associated with 
lakes or reservoirs.
    Adfluvial Arctic grayling repeatedly introduced into rivers have 
failed to establish viable populations (Kaya 1992b, pp. 12-14). 
Adaptive divergence and lack of ecological exchangeability between life 
history types are among the factors that may have contributed to these 
failures (Campton 2006, p. 13). However, introductions of fluvial 
grayling into other rivers within the native range have not been 
successful either, so success may be due to other factors (e.g., 
habitat degradation or competition with nonnative fish (Kaya 1992b, pp. 
10-12, 60)). In general, life history expression in salmonid species 
can be flexible, and Arctic grayling exhibit variation in migratory 
behavior across the range of the species (Northcote 1997, p. 1030). 
Geography may be a stronger determinant of ancestral relationships than 
life history for Arctic grayling. Native Arctic grayling populations 
within the upper Missouri River basin may be similar based on genetics, 
because they reside in the same river basin and presumably share a 
recent evolutionary ancestry (Campton 2006, p. 12), while at the same 
time expressing different life histories in response to local habitat 
conditions.

Previous Federal Action

    The Service initiated a status review for the Montana Arctic 
grayling (Thymallus arcticus montanus) through a notice of review 
published on December 30, 1982 (47 FR 58454). In that notice, Montana 
Arctic grayling was designated a Category 2 species, which included 
taxa for which information in possession of the Service at that time 
indicated that proposing to list the species as Endangered or 
Threatened was possibly appropriate, but for which substantial data 
were not currently available to biologically support a proposed rule 
(47 FR 58454). We received a petition, dated October 2, 1991, from the 
Biodiversity Legal Foundation and George Wuerthner on October 9, 1991. 
The petition requested that the ``fluvial Arctic grayling'' be listed 
as an endangered species throughout its historic range ``in the 
conterminous United States.''
    We published a notice of a 90-day finding in the January 19, 1993, 
Federal Register (58 FR 4975). In that 90-day finding we found that 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. We also found that because the 
Michigan population of Arctic grayling is extinct and, therefore, by 
definition cannot be listed, the finding would address only the fluvial 
population of the Arctic grayling in the upper Missouri River drainage.
    On July 25, 1994, we published a notice of a 12-month petition 
finding in the Federal Register concluding that listing the fluvial 
Arctic grayling indigenous to the upper Missouri River was warranted 
but precluded by other higher priority listing actions (59 FR 37738). 
This finding stated that the Service viewed adfluvial Arctic grayling 
as not under consideration in the Service's finding as it was believed 
to be a distinct population from the fluvial Arctic grayling. This 1994 
status review identified the fluvial form of Arctic grayling in the 
upper Missouri River drainage as a DPS based on its geographic 
isolation and behavioral distinctiveness (59 FR 37738-37741, July 25, 
1994). This status review occurred prior to the finalization of the 
Service and the National Marine Fisheries Service's joint DPS policy in 
1996 (61 FR 4722, February 7, 1996).
    Since 1994, and based on the best available information and the 
assessment that we conduct during our candidate review process, we have 
continued to preliminarily recognize the fluvial Arctic grayling of the 
upper Missouri River as a DPS, and has maintained it as a candidate 
species through the annual Candidate Notice of Review. In 2004, the 
Service elevated the listing priority number of the fluvial Arctic 
grayling to 3 (69 FR 24881, May 4, 2004) because the abundance of the 
remnant population in the Big Hole River declined substantially and 
reestablishment efforts had not yet produced self-sustaining 
populations elsewhere in the upper Missouri River.
    On May 31, 2003, the Center for Biological Diversity and Western 
Watersheds Project (collectively plaintiffs) filed a complaint in 
United States District Court in Washington, DC (1:03-cv-01110), 
challenging the Service's continuing ``warranted but precluded'' 
determination for fluvial Arctic grayling contained in the 2002 
Candidate Notice of Review (67 FR 40657, June 13, 2002). Plaintiffs 
filed an amended complaint on July 22, 2004, challenging the Service's 
failure to use its emergency listing authority to protect the fluvial 
Arctic grayling under the Act (16 U.S.C. 1531 et seq.). The litigation 
with plaintiffs was settled in August 2005. In this settlement 
agreement, the Service agreed that on or before April 16, 2007, it 
shall submit for publication in the Federal Register a final 
determination made pursuant to the Act as to whether or not the 
``Montana fluvial Arctic grayling'' is an endangered or threatened 
species. During the evaluation of the petition, the Service considered 
the term ``Montana fluvial Arctic grayling'' as synonymous with 
``fluvial Arctic grayling of the upper Missouri River.'' In this 
finding, as in the past, the fluvial form of the indigenous Arctic 
grayling from the upper Missouri River drainage in Montana and Wyoming 
is referred to as the fluvial Arctic grayling. This revised 12-month 
finding is being published as a final listing determination in 
accordance with the settlement agreement.

Distinct Vertebrate Population Segment

    Pursuant to the Act, we must consider for listing any species, 
subspecies, or, for vertebrates, any DPS of these taxa if there is 
sufficient information to indicate that such action may be warranted. 
The petition we received

[[Page 20311]]

concerns a potential DPS of fluvial Arctic grayling. Under our Policy 
Regarding the Recognition of Distinct Vertebrate Population Segments 
(61 FR 4722, February 7, 1996) (known as the DPS Policy), three 
elements are considered in a decision regarding the status of a 
possible DPS as endangered or threatened under the Act. These factors 
are applied similarly for additions to the Lists of Endangered and 
Threatened Wildlife and Plants (Lists), reclassification, and removal 
from the Lists. They are: (1) Discreteness of the population segment in 
relation to the remainder of the species to which it belongs; (2) the 
significance of the population segment to the species to which it 
belongs; and (3) the population segment's conservation status in 
relation to the Act's standards for listing (i.e., is the population 
segment, when treated as if it were a species, endangered or 
threatened?). Discreteness refers to the isolation of a population from 
other members of the species, and we evaluate this based on specific 
criteria that are also contained in the DPS Policy and are listed 
below. If the population segment is determined to be discrete, then we 
evaluate significance by using the available scientific information to 
determine the population segment's importance to the taxon to which it 
belongs. If we determine that a population segment is discrete and 
significant, we subsequently evaluate it for endangered or threatened 
status based on the Act's standards.

Discreteness

    Under our DPS Policy, a population segment of a vertebrate species 
may be considered discrete if it satisfies either one of the following 
conditions: (1) It is markedly separated from other populations of the 
same taxon as a consequence of physical, physiological, ecological, or 
behavioral factors. Quantitative measures of genetic or morphological 
discontinuity may provide evidence of this separation; or (2) It is 
delimited by international 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 Act.
    The subject of this DPS evaluation is the fluvial Arctic grayling 
of the upper Missouri River. In response to a petition, the fluvial 
Arctic grayling was the subject of a status review by the Service in 
1994, which identified Arctic grayling indigenous to the Big Hole and 
Madison Rivers as elements of a fluvial DPS in the upper Missouri River 
(59 FR 37738-37741, July 25, 1994). However, this status review 
occurred prior to the finalization of the Service and the National 
Marine Fisheries Service's joint DPS policy in 1996 (61 FR 4722, 
February 7, 1996). Since 1994, and most recently in 2004 and 2005, the 
Service reviewed the available information concerning the taxonomic 
status of the species in relation to the DPS policy and again 
preliminarily determined that the fluvial Arctic grayling of the upper 
Missouri River was a valid DPS (Service 2004, 2005). This DPS 
evaluation considers the information used in the previous assessments 
as well as a solicited review (Campton 2006) and unsolicited review 
(Leary 2005) of the available genetic data for Arctic grayling in 
Montana.

(1) Fluvial Arctic Grayling Are Discrete as a Consequence of Physical 
Features

    Fluvial arctic grayling native to the upper Missouri River are 
``markedly separated'' from other grayling, both those in Canada and 
Alaska, and from the adfluvial form in the Missouri River drainage 
because of physical and reproductive isolation. Fluvial actic grayling 
are geographically disjunct and reproductively isolated from 
populations inhabiting Arctic Ocean and Hudson Bay drainages in Canada 
and Alaska (Scott and Crossman 1973, p. 301). Arctic grayling in the 
upper Missouri River are reproductively isolated from their nearest 
conspecifics by at least 800 kilometers (km) (500 miles (mi)) (Nelson 
and Paetz 1991, p. 255) and have been separated from Arctic Ocean 
populations for perhaps 70,000 years as a result of glacial activity 
(Lynch and Vyse 1979, p. 263; Redenbach and Taylor 1999, p. 32). This 
long period of reproductive isolation coupled with genetic drift and 
environmental selection pressures has resulted in genetic differences 
between Arctic grayling from the Missouri River and elsewhere based on 
analyses of allozymes and mitochondrial DNA (Lynch and Vyse 1979, pp. 
263, 268, 275; Everett and Allendorf 1985, pp. 22-23, 26; Everett 1986, 
pp. 79-80; Redenbach and Taylor 1999, p. 23; reviewed by Campton 2006, 
pp. 5-6; reviewed by Leary 2005, pp. 1-3).
    Fluvial and adfluvial Arctic grayling within the upper Missouri 
River basin are ``markedly separated'' from each other as a result of 
physical features. The fluvial form was once widespread in the upper 
Missouri River basin, but the adfluvial form was native only to the Red 
Rocks Lakes and possible Elk Lake in the headwaters of the Beaverhead 
River (Kaya 1990). Extant populations of native fluvial and adfluvial 
Arctic grayling within the upper Missouri River are reproductively 
isolated, and the available genetic data are consistent with the 
hypothesis of two genetic groups of Arctic grayling (the Big Hole--
Madison River and Red Rock Lakes genetic groups) within the upper 
Missouri River (Leary 2005, p. 3; Campton 2006, pp. 6-9, 12)

(2) Fluvial Arctic Grayling Are Not Discrete as a Consequence of 
Physiological Features

    We do not believe that fluvial Arctic grayling are discrete because 
of unique or different physiological characteristics. Lohr et al. 
(1996) examined the thermal tolerance of juvenile fluvial Arctic 
grayling from the Big Hole River to elevated temperatures in laboratory 
tests. However, grayling from the Big Hole River did not appear to be 
more tolerant of warm stream temperatures than grayling from Alaska 
(Lohr et al. 1996, p. 937).
    Arctic grayling from the upper Missouri River tend to grow more 
quickly than individuals from northern populations (Northcote 1995, pp. 
156-157). However, experimental data are lacking that permit these 
differences to be attributed to environmental versus genetic 
influences.

(3) Fluvial Arctic Grayling Are Not Discrete as a Consequence of 
Ecological Features

    The Arctic grayling of the upper Missouri River represent the only 
natural example of the taxon inhabiting an Atlantic Ocean drainage (via 
the Missouri and Mississippi Rivers and Gulf of Mexico). All other wild 
populations of Arctic grayling inhabit drainages of the Arctic Ocean, 
Hudson Bay, or north Pacific Ocean (USFWS 2005, p. 10). However, 
fluvial Arctic grayling of the upper Missouri River basin are not 
discrete from adfluvial Arctic grayling of the upper Missouri River 
basin as a consequence of ecological features as they exist within a 
common drainage.

(4) Fluvial Arctic Grayling Are Discrete as a Consequence of Behavioral 
Features

    Under historical conditions within the upper Missouri River basin, 
native fluvial and adfluvial populations of Arctic grayling spawned in 
different locations (Vincent 1962, pp. 98-121; Kaya 1990, pp. 24-30; 
Kaya 1992a, pp. 47-53). Homing behavior to natal (birth) habitats that 
is typically expressed by Arctic grayling (e.g., Carl et al. 1992, p. 
245) would presumably result in the reproductive isolation of 
historical fluvial and adfluvial populations even if occasional 
exchange was possible. In

[[Page 20312]]

addition, genetic differences between the extant fluvial population in 
the Big Hole River and the native adfluvial population in Red Rock 
Lakes (e.g., Everett 1986, pp. 79-30; Leary 1990, pp. 7-8) are 
consistent with reproductive isolation between those populations based 
on observed differences in allozyme allele frequencies.
    Fluvial and adfluvial Arctic grayling do not appear to represent 
distinct lineages based strictly on life histories within the upper 
Missouri River system (e.g., Leary 2005, p. 3; Campton 2006, p. 12); 
there are clearly some heritable differences in juvenile swimming 
behavior among fluvial Arctic grayling and the native adfluvial 
populations in terms of rheotactic response to flowing water (Kaya 
1989, pp. 474, 478-479; Kaya 1991, pp. 53, 55-58; Kaya and Jeanes 1995, 
pp. 453-456). These differences in behavior are sufficient to satisfy 
the discreteness criterion of the DPS policy.
    On the basis of the available information, we conclude that the 
fluvial Arctic grayling of the upper Missouri River drainage is 
discrete from other populations of the same taxon as a consequence of 
physical and behavioral factors. Since a population segment of a 
vertebrate species may be considered discrete if the first factor is 
met (marked separateness), we need not address the second factor 
(delimitation by an international boundary). Therefore, we considered 
the potential significance of this discrete population to the remainder 
of the taxon.

Significance

    If a population segment is determined to be discrete, the Service 
considers the available scientific evidence of its significance to the 
taxon to which it belongs. Our policy states that this consideration 
may include, but is not limited to, the following:
    (1) Persistence of the discrete population segment in an ecological 
setting unusual or unique for the taxon;
    (2) Evidence that loss of the discrete population 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 a taxon that may be more abundant 
elsewhere as an introduced population outside its historic range; or
    (4) Evidence that the discrete population segment differs markedly 
from other populations of the species in its genetic characteristics.
    A population segment needs to satisfy only one of these criteria to 
be considered significant. Furthermore, the list of criteria is not 
exhaustive; other criteria may be used, as appropriate.

(1) Fluvial Arctic Grayling Do Not Persist in an Ecological Setting 
Unusual or Unique for the Taxon

    As discussed above, Arctic grayling generally occur throughout 
their native range in the holarctic region of Canada and Alaska to 
eastern Siberia and northern Eurasia (Scott and Crossman 1973, pp. 301-
302). In our 2005 candidate assessment, we asserted that the fluvial 
Arctic grayling of the upper Missouri River persist in an ecological 
setting unusual or unique for the taxon as they represent the only 
natural example of the taxon inhabiting an Atlantic Ocean drainage via 
the Missouri and Mississippi Rivers and Gulf of Mexico. We noted that 
all other wild populations of Arctic grayling inhabit drainages of the 
Arctic Ocean, Hudson Bay, or north Pacific Ocean (USFWS 2005, p. 10). 
However, as established above, we now note that adfluvial Arctic 
grayling also persist in the upper Missouri River drainage. Our prior 
finding did not take these fish into account in its discussion of 
ecological setting. Because both the fluvial and adfluvial forms are 
found in the upper Missouri drainage, we cannot find that the 
population persists in an ecological setting unique or unusual to the 
taxon as a whole.
    Further, existence of the species in a different drainage, or 
different rivers and lakes, from those grayling found in Canada and 
Alaska is not necessarily evidence of a unique ecological setting. 
Arctic grayling in the neararctic region are found in the same habitat 
type as those in Montana. Grayling inhabit clear water streams, rivers, 
and lakes. Riverine populations depend on large streams, deep pools of 
small streams, or spring-fed reaches that are not completely frozen in 
winter for overwinter survival. Populations not associated with lakes 
are found in both Alaska and Montana (Hubert 1985, p. 1). For this 
reason also, we find that fluvial Arctic grayling do not persist in an 
ecological setting unique or unusual for the taxon.

(2) The Loss of the Fluvial Arctic Grayling Would Not Result in a 
Significant Gap in the Range of the Taxon

    Loss of the fluvial Arctic grayling in the upper Missouri River, 
when considered in relation to grayling throughout the remainder of the 
nearctic region, would mean the loss of a small percentage of the 
entire range of the taxon. Due to the broad geographic range of Arctic 
grayling, the gap in the range of Arctic grayling resulting from the 
loss of fluvial Arctic grayling in the upper Missouri River basin would 
not result in a significant gap in the range of the taxon as a whole.
    In our 2005 candidate assessment, we asserted that the loss of the 
fluvial Arctic grayling of the upper Missouri River would result in a 
significant gap in the range of the taxon as these fish are the only 
extant fluvial grayling population in the contiguous United States and 
represent the southernmost extent of the species (USFWS 2005, p. 10). 
However, the Ninth Circuit Court has rejected this argument as a 
misconstruction of this criterion in the case of National Association 
of Home Builders v. Norton, 340 F. 3d 835, 852 (9th Cir. 2003) 
concerning the cactus ferruginous pygmy-owl (Glaucidium brasilianum 
cactorum) (70 FR 44551, August 3, 2005). The Court found that in 
designating a DPS under the DPS policy, we must find that a discrete 
population is significant to the taxon as a whole, not to the United 
States. Therefore, we have determined, based on the information 
available to the Service, the loss of the fluvial Arctic grayling in 
the upper Missouri River would not result in a significant gap in the 
range of the species on the basis of the significance of the Montana 
population to the species as a whole.

(3) Fluvial Arctic Grayling Do Not Represent the Only Surviving Natural 
Occurrence of the Taxon

    This criterion from the DPS policy does not apply to the fluvial 
Arctic grayling in the upper Missouri River because it is clearly not a 
population segment representing the only surviving natural occurrence 
of a taxon that may be more abundant elsewhere as an introduced 
population outside its historic range. Consequently, this population of 
grayling is not significant according to this standard.

(4) Fluvial Arctic Grayling in the Missouri River Drainage Do Not 
Differ Markedly in Genetic Characteristics From Adfluvial Populations 
in the Missouri River Drainage

    As noted above, analyses of allozymes and mitochondrial DNA show 
genetic divergence between Arctic grayling in the upper Missouri River 
and Arctic grayling in Canada and Alaska (Lynch and Vyse 1979, pp. 263, 
268, 275; Everett and Allendorf 1985, pp. 22-23, 26; Everett 1986, pp. 
79-80; Redenbach and Taylor 1999, p. 23; reviewed by Campton 2006, pp. 
5-6; reviewed by Leary 2005, pp. 1-3) and appear to be most closely 
related evolutionarily to populations in northeastern

[[Page 20313]]

Saskatchewan, Canada (Stamford and Taylor 2004, p. 1538).
    In addition, fluvial Arctic grayling from the Big Hole River are 
genetically different from native adfluvial Arctic grayling in Red Rock 
Lakes based on observed differences in allozyme allele frequencies 
(Campton 2006, p. 6). However, the relative genetic difference between 
these two groups within the upper Missouri River basin is less than 
that between upper Missouri River Arctic grayling and sample 
populations from Alaska and Canada (Leary 1990, pp. 1, 7-8).
    Resolving ancestries among recently diverged upper Missouri River 
Arctic grayling populations is difficult due to the low allozyme 
variability among samples (Leary 2005, pp. 3-4; Campton 2006, p. 10). 
In this case, although allozyme data from 39 loci are available from 
these populations, only 2 of the loci analyzed were generally variable 
among them (Everett 1986; Leary 1990; Leary 2005, p. 3). Information 
from only two loci may cause chance similarities or differences and 
require cautious interpretation (Leary 2005, p. 3).
    Likewise, the paucity of genetic variation detected by Redenbach 
and Taylor (1999, p. 27) in their restriction enzyme analysis of mtDNA 
of upper Missouri River basin Arctic grayling precludes making any 
inferences about genetic similarities or differences among the upper 
Missouri River populations sampled except that they all appear to share 
a common maternal lineage (Leary 2005, p. 4). The level of genetic 
divergence observed among populations within the upper Missouri River 
is consistent with what would be expected for populations within a 
geographic area that share a recent ancestry (Campton 2006, p. 12).
    Discerning genetic divergence among Arctic grayling populations is 
further complicated by the extensive hatchery propagation and 
transplantation of stocks, as discussed above (Everett 1986, p. 40). 
The Service does not regard the introduced, lake-dwelling grayling to 
be part of the indigenous upper Missouri River fluvial Arctic grayling 
population (59 FR 37739, July 25, 1994). However, widespread stocking 
of hatchery-reared Arctic grayling in the Big Hole River system and 
other locations (e.g., Everett 1986, pp. 4, 16; Kaya 1990, pp. 31, 75-
80) makes it possible that some fish are introduced populations or that 
the existing populations are a mixture of native and introduced Arctic 
grayling.
    We find that, based on the genetic information currently available, 
the fluvial Arctic grayling of the upper Missouri River drainage do not 
differ markedly from adfluvial populations of the species in their 
genetic characteristics such that they should be considered 
biologically or ecologically significant based simply on genetic 
characteristics. Biological and ecological significance under the DPS 
policy is always considered in light of Congressional guidance (see 
Senate Report 151, 96th Congress, 1st Session) that the authority to 
list DPSs be used ``sparingly'' while encouraging the conservation of 
genetic diversity.

Conclusion on DPS

    Under section 3 of the Act and our implementing regulations at 50 
CFR 424.02, a ``species'' is defined to include any species or 
subspecies of fish, wildlife, or plant, and any distinct population 
segment of any vertebrate species which interbreeds when mature. Our 
implementing regulations provide further guidance on determining 
whether a particular taxon or population is a species or subspecies for 
the purposes of the Act: ``The Secretary shall rely on standard 
taxonomic distinctions and the biological expertise of the Department 
and the scientific community concerning the relevant taxonomic group'' 
(50 CFR 424.11). As noted above, Arctic grayling in the upper Missouri 
River basin have been classified into separate species and subspecies, 
but these designations are not widely accepted. Therefore, we do not 
consider the subject of this petition to constitute a distinct species 
or subspecies.
    The 1994 status review identified the fluvial form of Arctic 
grayling in the upper Missouri River drainage as a DPS based on its 
geographic isolation and behavioral distinctiveness (59 FR 37738, July 
25, 1994). On the basis of the best available information, we continue 
to conclude that the fluvial Arctic grayling of the upper Missouri 
River drainage is ``markedly separated'' from all other populations of 
the same taxon as a consequence of physical and behavioral factors. 
Consequently, the Service concludes that the petitioned entity is 
discrete according to the 1996 DPS policy. However, on the basis of the 
four significance criteria in the 1996 DPS Policy, the Service is 
unable to conclude at this time that the petitioned entity is 
significant. Therefore, we find that the fluvial Arctic grayling of the 
upper Missouri River does not qualify as a distinct population segment 
under the Act.

Significant Portion of the Range

    Pursuant to the Act and our implementing regulations, a species may 
warrant listing if it is threatened or endangered in a significant 
portion of its range. However, the petition did not request that we 
determine whether the grayling was threatened or endangered in a 
significant portion of its range. Rather, it asked that we list the 
fluvial Arctic grayling in the U.S. as an endangered species. 
Consistent with the petition, our previous petition findings have 
uniformly addressed possible listing in the context of whether the 
fluvial Arctic grayling in Montana constitutes a DPS, and therefore a 
``species'' under the Act. As discussed above, we have now determined 
that the fluvial Arctic grayling is not a DPS. Thus, we have disposed 
of the question raised by the petition: we have no obligation under the 
Act to address the separate question of whether the fluvial Arctic 
grayling in Montana constitutes a significant portion of the range of 
some of the entire grayling species, or some valid but currently 
undefined DPS. If the Service determines in the future that the 
grayling is threatened or endangered in a significant portion of its 
range, we will add the species to the candidate list and propose its 
listing. However, that would be a future action. Because the petition 
and our prior finding were with respect to a DPS, and we have found 
that there is not a valid DPS, we do not need to address significant 
portion of the range at this time.

Finding

    On the basis of the discussion presented in this document, we find 
that the fluvial Arctic grayling of the upper Missouri River does not 
qualify as a distinct population segment. As a result, we find that the 
petition to list the fluvial Arctic grayling of the upper Missouri 
River is not warranted. Based on this determination, we withdraw the 
fluvial Arctic grayling of the upper Missouri River from the candidate 
list. Although no further action will result from this finding, we 
request that you submit new information concerning the taxonomy, 
biology, ecology, and status of the Arctic grayling of the upper 
Missouri River system to the Montana Field Office (see ADDRESSES below) 
whenever it becomes available. We will accept additional information 
and comments from all concerned governmental agencies, the scientific 
community, industry, or any other interested party concerning this 
finding; and will reconsider this determination in the event of new 
information as appropriate. The Service continues to strongly encourage 
cooperative conservation and restoration of fluvial Arctic grayling in 
the upper Missouri River.

[[Page 20314]]

References

    A complete list of all references cited herein is available upon 
request from the Montana Field Office, U.S. Fish and Wildlife Service 
(see ADDRESSES).

Author

    The authors of this finding are biologists in Region 6 of the U.S. 
Fish and Wildlife Service.

Authority

    The authority for this action is the Endangered Species Act of 
1973, as amended (16 U.S.C. 1531 et seq.).

    Dated: April 13, 2007.
H. Dale Hall,
Director, Fish and Wildlife Service.
 [FR Doc. E7-7484 Filed 4-23-07; 8:45 am]
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