Endangered and Threatened Wildlife and Plants; 12-Month Finding on a Petition To List the Coaster Brook Trout as Endangered, 23376-23388 [E9-11527]

Agencies

• Fish and Wildlife Service
• DEPARTMENT OF THE INTERIOR

[Federal Register Volume 74, Number 95 (Tuesday, May 19, 2009)]
[Proposed Rules]
[Pages 23376-23388]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: E9-11527]


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DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

[FWS-R3-ES-2008-0030; 92210-1111-0000-FY09-B3]


Endangered and Threatened Wildlife and Plants; 12-Month Finding 
on a Petition To List the Coaster Brook Trout as Endangered

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Notice of 12-month petition finding.

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SUMMARY: We, the U.S. Fish and Wildlife Service (Service), announce a 
12-month finding on a petition to list the coaster brook trout 
(Salvelinus fontinalis) as endangered under the Endangered Species Act 
of 1973, as amended (Act). The petition also asked that critical 
habitat be designated for the species. After review of all available 
scientific and commercial information, we find that the coaster brook 
trout is not a listable entity under the Act, and therefore, listing is 
not warranted. We ask the public to continue to submit to us any new 
information that becomes available concerning the taxonomy, biology, 
ecology, and status of coaster brook trout and to support cooperative 
conservation of coaster brook trout within its historical range in the 
Great Lakes.

DATES: The finding announced in this document was made on May 19, 2009.

ADDRESSES: This finding is available on the Internet at https://www.regulations.gov at Docket Number [FWS-R3-ES-2008-0030]. Supporting 
documentation for this finding is available for inspection, by 
appointment, during normal business hours at the U.S. Fish and Wildlife 
Service, Region 3 Fish and Wildlife Service Regional Office, 1 Federal 
Drive, Bishop Henry Whipple Federal Building, Fort Snelling, MN 55111. 
Please submit any new information, materials, comments, or questions 
concerning this finding to the above address, Attention: Coaster brook 
trout.

FOR FURTHER INFORMATION CONTACT: Jessica Hogrefe, Region 3 Fish and 
Wildlife Service Regional Office (see ADDRESSES) (telephone 612-713-
5346; facsimile 612-713-5292). 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 Act (16 U.S.C. 1531 et seq.) requires 
that, for any petition to revise the Lists of Endangered and Threatened 
Wildlife and Plants that contains substantial scientific and commercial 
information that listing may be warranted, we make a finding within 12 
months of the date of our receipt of the petition on whether the 
petitioned action is: (a) Not warranted, (b) warranted, or (c) 
warranted, but the immediate proposal of a regulation implementing the 
petitioned action is precluded by other pending proposals to determine 
whether species are threatened or endangered, and expeditious progress 
is being made to add or remove qualified species from the List of 
Endangered and Threatened Species. Section 4(b)(3)(C) of the Act 
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 that we make a subsequent finding 
within 12 months. Such 12-month findings must be published in the 
Federal Register. This notice constitutes our 12-month finding for the 
petition to list the U.S. population of coaster brook trout.

Previous Federal Action

    The Sierra Club Mackinac Chapter, Huron Mountain Club, and Marvin 
J. Roberson filed a petition, dated February 22, 2006, with the 
Secretary of the Interior to list as endangered the ``naturally 
spawning anadromous (lake-run) coaster brook trout throughout its known 
historic range in the conterminous United States'' and to designate 
critical habitat under the Act. The petition clearly identified itself 
as such and included the requisite identification information for the 
petitioners, as required in 50 CFR 424.14(a). On behalf of the 
petitioners, Peter Kryn Dykema, Secretary of the Huron Mountain Club, 
submitted supplemental information, dated May 23, 2006, in support of 
the original petition. This supplemental information provided further 
information on the species' status and biology, particularly for brook 
trout in the Salmon Trout River.
    On September 13, 2007, we received a 60-day notice of intent to sue 
over the Service's failure to determine, within 1 year of receiving the 
petition, whether the coaster brook trout warrants listing. Under 
section 4 of the Act, the Service is to make a finding, to the maximum 
extent practicable within 90 days of receiving a petition, that it does 
or does not present substantial scientific or commercial information 
indicating that the petitioned action may be warranted. Further, the 
Act requires that, within 12 months of receiving a petition found to 
present substantial information, the Service must determine whether the 
petitioned action is warranted. A complaint was filed in U.S. District 
Court in the District of Columbia on December 17, 2007, for failure to 
make a timely finding (Sierra Club, et al. v. Kempthorne, No. 1:07-cv-
02261 (D.D.C. December 17, 2007)). The Service reached a negotiated 
settlement with the plaintiffs to submit the 90-day finding to the 
Federal Register by March 15, 2008. We published a ``substantial'' 90-
day finding March 20, 2008. The negotiated settlement further required 
the Service to publish the 12-month finding in the Federal Register by 
December 15, 2008. The deadline for the 12-month finding was extended 
to April 15, 2009, by mutual consent. On April 15, 2009, we filed an 
unopposed motion to extend the deadline for the coaster brook trout 12-
month finding to May 12, 2009.

Species Information

Species Description
    Brook trout (Salvelinus fontinalis), also called brook char or 
speckled trout, is one of three species in the genus Salvelinus (chars) 
native to north and eastern North America; the others being lake trout 
(S. namaycush) and Arctic char (S. alpinus). The chars are a sub-group 
of fishes in the salmon and trout subfamily (Salmoninae) that is 
distinct from the ``true'' trout and salmon sub-groups.
    The brook trout throughout its range in eastern North America 
exhibits considerable variation in growth rate, color, and other 
features, but generally can be distinguished from other char and trout 
species by its olive-green to dark brown back with a light yellow-brown 
vermiculate pattern, sides with large yellow-brown spots and blue halos 
surrounding small, sporadic red and orange spots. Pectoral, pelvic, 
anal, and lower caudal fin have leading edges of white bordered by 
black with the

[[Page 23377]]

remainder predominantly reddish to orange. Sea-run brook trout become 
silver with purple iridescence and show red spots on the sides (Scott 
and Crossman 1973, p. 208).
Distribution
    The historical range of native brook trout extends along Hudson Bay 
in Canada across the Provinces of Manitoba, Ontario and Quebec, to 
Newfoundland and Labrador and south to Nova Scotia and New Brunswick in 
Canada; and from eastern Iowa through northern Illinois, northern Ohio, 
and the Great Lakes drainage (Minnesota, Michigan, Wisconsin), through 
the New England States (New York, New Hampshire, Vermont, Maine, 
Massachusetts, Pennsylvania, New Jersey), large New England rivers 
(such as the Hudson River and Connecticut River), and through the 
Appalachian Mountains in Maryland, Virginia, West Virginia, North 
Carolina, South Carolina, Tennessee, south to Georgia (MacCrimmon and 
Campbell 1969, pp. 1700-1702; MacCrimmon et al. 1971, p. 452; Scott and 
Crossman 1973, pp. 209-210; Power 1980, p. 142). Naturalized 
populations of brook trout were established as early as the late 1800s 
beyond the historical native range by introductions to waters in 
western North America, South America, Eurasia, Africa, and New Zealand 
(MacCrimmon and Campbell 1969, p. 1699, pp. 1703-1717). The current 
range of native brook trout still extends through Canada and down to 
Georgia in the U.S., but in many locations, populations have been 
completely extirpated or have contracted within this range towards 
upper stream reaches, higher altitudes, or headwaters (EBJV 2006, p. 
2).
Distribution of Brook Trout in the Great Lakes
    According to Bailey and Smith (1981, p. 1549) and MacCrimmon and 
Campbell (1969, p. 1701), brook trout are native to the lakes and 
tributaries of Lakes Superior, Huron, Michigan, and the tributaries of 
Lakes Erie and Ontario. Brook trout are not believed to have been 
present in Minnesota streams above barrier falls to Lake Superior 
(Smith and Moyle 1944, p. 119) or throughout most of the lower 
peninsula of Michigan (MIDNR 2008a, pp. 1-2; MacCrimmon and Campbell 
1969, p. 1704).
Habitat Requirements
    Brook trout require clear, cold, well-oxygenated water to thrive. 
They are generally found in water ranging between 41-68[deg] Fahrenheit 
(5-20[deg] Celsius), with their likely preferred temperature falling 
near the middle of this range (Power 1980, p. 172). Thermal 
requirements within this range vary by life cycle phase and season 
(Scott and Crossman 1973, p. 211; Blanchfield and Ridgway 1997, p. 750; 
Baril and Magnan 2002, pp. 177-178).
    The brook trout spawns in late summer or autumn, the date varying 
with latitude and temperature. Spawning takes place most often over 
gravel beds but may be successfully accomplished over a variety of 
substrates if there is spring upwelling or a moderate current (Scott 
and Crossman 1973, p. 210). Power (1980, p. 151) describes rangewide 
brook trout spawning, which occurs in the fall, when day length and 
temperature are decreasing. In northerly regions and at high 
elevations, brook trout may spawn as early as late August and spawning 
may be delayed until December in southern areas. As is typical for 
salmonids, females prepare redds (hollows scooped out for spawning) in 
suitable gravel substrate. The female then deposits her eggs in the 
redd where they are fertilized by a male. After spawning there is no 
further parental involvement with the young. The redd protects the eggs 
and allows an adequate exchange of dissolved gases and other materials 
during development.
    Brook trout are carnivorous, feeding opportunistically upon a 
variety of prey, such as worms, leeches, crustaceans, aquatic insects, 
terrestrial insects, spiders, mollusks, and fish (Scott and Crossman 
1973, p. 212). Anadromous (migrating from salt water to spawn in fresh 
water) forms vary their feeding behavior and prey items based on their 
age and the environment, marine or riverine, they are occupying (Newman 
and Dubois 1997, p. 9). Brook trout also show diverse foraging 
behaviors; some individuals may be sedentary, eating crustaceans from 
the lower portion of the water column, whereas others in the same 
system may be more active and eat insects from the upper portion of the 
water column (McLaughlin et al. 1999, p. 386). This resource 
polymorphism may play a supplementary role in the extensive adaptive 
radiation (evolution of ecological variability within a rapidly 
multiplying lineage; Smith and Sk[uacute]lason 1996) observed in this 
species.
Genetics of Brook Trout
    A large amount of genetic variation for brook trout is 
distributed among populations (large Fst values). This pattern is 
heavily influenced by the diverse ecological and life-history 
characteristics of brook trout populations (population connectivity 
or isolation, philopatric tendency). This pattern of highly 
differentiated populations of brook trout is found at small and 
large geographic scales. Population genetic structuring is common in 
brook trout throughout its range (Angers et al. 1999, pp. 1049-
1050). Like many salmonids, brook trout tend to have a hierarchical 
population structure resulting from the hierarchical design of the 
networks of streams and lake or coastal areas in which they live, 
and a complicated life cycle that leads to strong local adaptations. 
Taxonomic resolution can be even more complicated at the lake level 
when lakes include sympatric (occupying the same or overlapping 
geographic area without interbreeding) but genetically divergent 
brook trout populations such as in Lake Mistassini in Canada (Fraser 
and Bernatchez 2008, p. 1197). This degree of genetic divergence 
that forms among populations is reflective of the reproductive 
connections (isolation) among the populations across the range of 
the taxon.

    Six distinct genetic mitochondrial (mtDNA) clades have been 
identified throughout the range of brook trout in eastern North America 
(Danzmann et al. 1998, p. 1307). These mtDNA clades reflect historical 
isolation in glacial refugia or long periods of isolation in nonglacial 
areas in the southern part of the species' range. The Wisconsin glacial 
advance which covered portions of Canada covered all five Great Lakes 
15,000 years ago (Bailey and Smith 1981, p. 1543). As these glaciers 
receded, brook trout recolonized the lakes from the Mississippi and 
Atlantic refugia (Danzmann et al. 1998, pp. 1308, 1312). Given this 
pattern of glaciation, genetic diversity is greatest at the southern 
portion of the species' range and gradually decreases northward 
(Danzmann et al. 1998, pp. 1310-1311). As the most geographically 
isolated (for tens of thousands of years), brook trout in the southern 
part of the species' range (along the Appalachian Mountains south to 
Georgia) are the most diverse, containing all six mtDNA clades. The 
Great Lakes contains three of the six mtDNA clades. Throughout the 
northern portion of their range in Canada, brook trout are the least 
genetically diverse, with only a single mtDNA clade present. Within 
each of these lineages, there is evidence to suggest that selection is 
driving rapid phenotypic divergence in some populations.
    Results based on microsatellite DNA variation identified nine 
distinct genetic assemblages of brook trout in the U.S. (King 2009, 
unpub. data). Assemblages from the nonglacial southern part of the 
species' range (along the Appalachian Mountains from Pennsylvania to 
Georgia) in the U.S. are the most genetically divergent, and this 
divergence among the assemblages generally decreases as the range 
progresses northward.

[[Page 23378]]

Genetics of Brook Trout in the Great Lakes
    Populations from Lake Superior and tributaries to Lake Erie form 
two of the nine genetic assemblages of brook trout in the U.S. The Lake 
Erie populations are the most divergent assemblage from the northern 
part of the species' range. Lake Superior populations are similar in 
the degree of genetic divergence to the remaining northern assemblages 
grouping with the average genetic distance between brook trout 
populations in the U.S. Samples from the rest of the Great Lakes were 
not available for analysis. Although brook trout in the Great Lakes do 
not contain any wholly unique mtDNA clades, they do contain a large 
amount of the genetic variation in a confined portion of the range 
(Danzmann et al. 1998, pp. 1310-1311).
    Native populations of brook trout in Lake Superior in most cases 
have retained their native genetic characteristics despite the stocking 
of hatchery fish from sources outside and within the Lake Superior 
basin. In Lake Superior, the intensity and purpose of stocking has 
varied over time and space. For example, Minnesota tributaries to Lake 
Superior have been stocked with hatchery strains that originated from 
outside of the Great Lakes Basin to provide fishing opportunities above 
fish passage barriers (Wilson et al. 2008, p. 1312). Until the early 
1990s, most of the stocked fish in Lake Superior were domesticated 
strains from outside the Great Lakes basin (Schreiner et al. 2008, p. 
1357), although many stocking events were undocumented and records of 
early stocking events are incomplete (Wilson et al. 2008, p. 1312). 
These stocking efforts were not targeted at rehabilitation and from 
that perspective, results were poor. The stocked fish were not 
behaviorally or evolutionarily adapted to the environment in which they 
were planted, criteria known to limit survival and reproductive success 
(Schreiner et al. 2008, p. 1357). Burnham-Curtis (2001, p. 2) concluded 
that hatchery fish have had little reproductive success in Lake 
Superior streams based on her examination of 36 tributaries to Lake 
Superior and 9 hatchery stocks outplanted into the lake. However, the 
genetic methods used by Burnham-Curtis provided low power to detect 
genetic introgression of hatchery fish into native populations (Wilson 
et al. 2008, p. 1312). A recent study by D'Amelio and Wilson (2008, p. 
1215) used genetic methods with high power to detect genetic 
introgression of hatchery fish into natural populations. This study 
documented only low levels of genetic introgression of Lake Nipigon 
hatchery fish into native populations of brook trout from six 
tributaries to Lake Superior's Nipigon Bay (D'Amelio and Wilson 2008, 
p. 1222), despite decades of stocking. A study by Scribner et al. 
(2006, pp. 3-4) examined nine brook trout populations from Lake 
Superior tributaries on the south shore of Michigan and four hatchery 
strains outplanted into those tributaries. This study used similar 
methods to D'Amelio and Wilson (2008). Scribner et al. (2006, p. 8) 
concluded that hatchery stocking appears to have minimal if any impact 
of on brook trout.
Brook Trout Life-History Diversity
    An individual's ability to produce multiple phenotypes (visible or 
observable characteristics) in response to its environment is termed 
phenotypic plasticity (Scheiner 1993, p. 36). Recent studies have 
recognized the role of phenotypic plasticity as a major source of 
phenotypic variation in natural populations (Price et al. 2003, p. 
1438). The brook trout exhibits remarkable phenotypic plasticity across 
its natural range. This plasticity allows it to thrive in a variety of 
environments, from cold subarctic regions, through temperate zones and 
in southern refugia in eastern North America, and in a range of places 
where it has been introduced (Power 1980, p. 142). Although primarily a 
stream-dwelling species, brook trout also occupy inland lakes and 
coastal waters. Because of the variety of the freshwater, estuary, and 
ocean environments, migratory plasticity is also favored. The brook 
trout's dispersal subsequent to receding glaciation, and separation 
into isolated breeding stocks in diverse habitats subject to an array 
of natural and man-made influences have all contributed to this 
variability (Power 1980, p. 142).
    Brook trout display considerable life-history variation throughout 
their native range (Huckins and Baker 2008, p. 1229). Brook trout 
across its range exhibit a variety of life-history types (polymorphisms 
or ecotypes), including fluvial (stream-dwelling), adfluvial (migrating 
between lakes and streams), lacustrine (lake-dwelling), and anadromous 
(migrating from salt water to spawn in fresh water) forms. 
Understanding life-history diversity in a species requires knowledge of 
the evolutionary history, ecological setting, and reproductive 
relationships among ecotypes. Reproductive interactions between 
ecotypes are reflected by the magnitude and pattern of genetic 
differentiation observed between life-history phenotypes at neutral 
genetic markers. The expression of migratory behavior (expressed as the 
adfluvial and anadromous ecotypes) by any individual fish will be 
partially in direct response to its environment. Phenotypic expression 
of more than one form may be expected in a population located in a 
variable environment containing habitats for several ecotypes. The 
amount of phenotypic plasticity a population will exhibit for the 
migratory trait also has a heritable genetic basis and will be 
determined by the intensity and type of selective pressures that 
population experiences (Via and Lande 1985, pp. 517-519; Theriault et 
al. 2008, pp. 418-419).
    Adoption of migratory adfluvial form or stream-resident life-
history form in brook trout has been modeled under a conditional 
strategy framework where environmentally influenced threshold traits 
determine which ecotype a fish will adopt (Hendry et al. 2004, pp. 124-
125). Growth rate efficiencies, body size, and concentration of 
juvenile hormone have all been identified as potential threshold traits 
(Theriault and Dodson 2003, pp. 1155-1157). Theoretical work by Ridgway 
(2008, p. 1185) and Uller (2008, pp. 436-437) also provide information 
to suggest parental effects are important to the expression of 
alternate ecotypes of brook trout. These parental effects describe an 
affect of the parental phenotype on the offspring's phenotype such as 
coaster females producing larger eggs and spawning in different 
locations from stream-resident ecotypes, influencing the habitat use 
(Morinville and Rasmussen 2006, pp. 701-702) and growth rate at the 
juvenile stage (Perry et al. 2005, p. 1358). These differences in 
growth rate and habitat use impact potential threshold traits.
    Work on sympatric brook trout life forms at young ages largely 
comes from a few studies on anadromous populations. Morinville and 
Rasmussen (2003) studied the bioenergetics of young brook trout 
exhibiting anadromous migratory and stream-resident life tactics. They 
found that the anadromous migrants have higher metabolic costs and had 
consumption rates 1.4 times that of stream residents but growth 
efficiencies of the anadromous form were lower than that of residents. 
Spatial utilization of habitat differed among the life tactics as well, 
with migratory individuals occupying faster-flowing waters compared to 
the resident fish which used pool areas (p. 408). They concluded that 
migrant brook trout have noticeably different energy budgets than 
resident brook trout from the same system (p. 406). Morinville and 
Rasmussen (2008) also investigated morphological differences between 
life

[[Page 23379]]

tactics. The authors concluded that migrant brook trout were found to 
be more streamlined (narrower and shallower bodies) than resident brook 
trout, and these differences persisted into the marine life of the 
migrant fish (pp. 175, 183). The differences were powerful enough to 
derive discriminant functions using five of the measured traits 
allowing for accurate classification of juvenile brook trout as either 
migrant or resident with an overall correct classification rate of 87 
percent.
    A study by Theriault et al. (2007b, p. 61) found that sympatric 
anadromous and fluvial brook trout in the Sainte-Marguerite River in 
Quebec belonged to a single gene pool. Phenotypic plasticity is, 
therefore, a major force driving the expression of these two life 
histories from this population. Evolution of phenotypic plasticity in 
this population was influenced by mating systems with most of the 
mating between different morphotypes occurring between fluvial males 
and anadromous females. Additional work in this system demonstrated 
significant heritability for life-history tactic and for body size 
(Theriault et al. 2007a, pp. 7-8) indicating expression of life-history 
tactic in this population can be effected by natural or artificial 
selection.
Life-History Diversity in Great Lakes Brook Trout
    Fish that complete their life cycle exclusively in tributaries to 
the Great Lakes exhibit the fluvial life history and are defined as 
stream residents. ``Coaster'' (the subject of the petition) is a 
regional term for a life-history variant of brook trout in the Great 
Lakes (Burnham-Curtis 2001, p. 2; Wilson et al. 2008, p. 1) which use 
lake waters of the Great Lakes for all or a portion of its life cycle 
(Becker 1983, p. 320). The coaster form can be further divided into an 
adfluvial ecotype that migrates from the stream to the lake and back 
into tributaries to spawn and a lacustrine ecotype that completes its 
life cycle entirely within the lake (Huckins et al. 2008, p. 1323). In 
the Great Lakes region, spawning usually occurs from mid-September 
through mid-November. Distinct life histories associated with the 
coaster and stream-resident types result in different physical, 
demographic, and ecological characteristics for the forms (Huckins et 
al. 2008, p. 1337; Huckins and Baker 2008, p. 1241; Ridgway 2008, p. 
1185). Specifically, coasters tend to live longer than stream residents 
(5-8 years versus less than 5 years), reach maturation later (females 
at 2-4 years versus 1-2 years), attain larger length and weight as 
adults (12-25 inches and 0.75-8 pounds (30-64 centimeters (cm) and 341-
3632 grams (g)) versus (5-15 inches (13-38 cm) and (less than 1 pound 
(<454 g), be more fecund (1500-3000 eggs per female versus 100-1500 
eggs per female), and move greater distances (up to 19-217 miles (30-
350 kilometers (km)) versus less than 19 miles (30 km)) (Scott and 
Crossman 1973, pp. 208, 210, 211; Power 1980, p. 157; Becker 1983, pp. 
318, 320; Ritchie and Black 1988, pp. 19, 50, 51; Quinlan 1999, pp. 11, 
12, 14, 16, 17, 20; Swainson 2001, pp. 40, 41, 60, 64; WIDNR and USFWS 
2005, p. 16; Huckins and Baker 2008, pp. 1239, 1241; Huckins et al. 
2008, pp. 1328, 1329, 1337; Mucha and Mackereth 2008, p. 1210; Schram 
2008a, pers. comm.; Chase 2008, pers. comm.).
    Coasters have been historically documented in Lakes Superior, 
Huron, and Michigan brook trout populations (Bailey and Smith 1981, p. 
1549; Dehring and Krueger 1985, p. 1; Enterline 2000, p. 1; MIDNR 
2008a, pp. 1-2). However, Lake Superior is the only Great Lake with 
extant coaster forms of brook trout, and all available literature is 
from this area. Coasters in the Great Lakes are found in Canada and the 
U.S. in substantially fewer locations than they were historically 
(Newman et al. 2003, p. 39). Populations in the Great Lakes basin with 
these life-history forms are documented within Canada in tributaries to 
Nipigon and Black Bays, the Nipigon River, Lake Nipigon and the Pancake 
River in the eastern part of Lake Superior (Newman et al. 2003, p. 39; 
Chase and Swainson 2009, pers. comm.). Within the U.S. portion of the 
Great Lakes basin, populations that express the coaster form occur in 
Isle Royale National Park in Tobin Harbor, Big and Little Siskiwit 
Rivers, and Washington Creek as well as on the south shore of Lake 
Superior in the Salmon Trout River (Newman et al. 2003, p. 39).
    As previously stated, brook trout populations within the upper 
Great Lakes exhibit fluvial, adfluvial, and lacustrine life-history 
forms, coasters comprising the latter two forms. Populations of brook 
trout in Lake Superior likely function as types of metapopulations, 
with the coaster life forms serving as dispersers (D'Amelio and Wilson 
2008, p. 1222; Sloss et al. 2008, p. 1249). The viability of a 
metapopulation is strongly contingent upon maintaining dispersal among 
populations. Although brook trout exhibit spawning site fidelity, 
individuals exhibiting the adfluvial life forms in Lake Superior have 
also been shown to stray or disperse among streams (D'Amelio and Wilson 
2008, p. 1222; Mucha and Mackereth, p. 1211). The long-term persistence 
of a metapopulation requires a balance between local extinction and 
recolonization of constituent populations (see Hanski 1998 for a review 
of metapopulations). Dispersing individuals offset local population 
extinction by providing a means for recolonization (Brown and Kodric-
Brown 1977, p. 448; Reeves et al. 1995, p. 340). Dispersing individuals 
also provide for gene flow among discrete populations, countering 
losses of genetic fitness while still allowing the development and 
distribution of unique adaptive traits (Ingvarsson 2001, p. 63; Tallmon 
et al. 2004, p. 494). Thus, the coaster life-history forms are 
important to the long-term viability of brook trout populations 
throughout Lake Superior.
    Genetic studies of stream-resident (fluvial life form) brook trout 
show substantial genetic structuring among populations in Michigan, 
Wisconsin, Minnesota, and Canada characterized by distinct regional 
groupings or metapopulations (Burnham-Curtis 1996, pp. 10-11; Burnham-
Curtis 2001, p. 10; Sloss et al. 2008, p. 1249; Wilson et al. 2008, p. 
1312; Scribner et al. 2008, p. 9). In studies aimed at determining 
genetic differences between the coaster polymorphism and stream-
resident fish occupying tributaries connected to the lake, molecular 
genetic work in Lake Superior indicates that coasters and stream-
resident brook trout occupying tributaries to the first barrier are 
parts of the same population (D'Amelio and Wilson. 2008, p. 1221; 
Scribner et al. 2008, p. 9; Stott 2008, p. 5). Work investigating the 
genetic differences of various tributaries to the lake found distinct 
differences among populations of brook trout in each tributary to Lake 
Superior (Burnham-Curtis 1996, p. 10; Burnham-Curtis 2000, p. 7; 
Burnham-Curtis 2001, p. 10; D'Amelio and Wilson 2008, p. 1222; Sloss et 
al. 2008, p. 1249; Scribner et al. 2008, p. 9). Within Lake Superior, 
regional genetic differences are evident between brook trout 
populations in Nipigon Bay, Isle Royale, and Lake Nipigon-Grand Portage 
(Wilson et al. 2008, p. 1313). Adfluvial brook trout are thought to be 
the mechanism providing genetic communication among these regional 
aggregations and straying of a coaster was documented in Nipigon Bay 
and at Isle Royale (D'Amelio et al. 2008, p. 1347; Stott 2008, p. 4). 
Sloss et al. (2008) investigated genetic differentiation among four 
Wisconsin populations of stream-resident brook trout. His work found 
significant differentiation among populations to the point the authors 
observed that for these populations,

[[Page 23380]]

there appears to be a near complete lack of gene flow among them 
resulting in genetic drift (Sloss et al. 2008, p. 1249). None of these 
isolated populations are thought to currently have adfluvial ecotypes 
as part of the population. This observation is consistent with the 
contemporary lack of an adfluvial form that historically provided the 
regional genetic connection for the three metapopulations previously 
mentioned.
    As characterized in the entire brook trout species, phenotypic 
plasticity and adaptive radiation (Schluter 2000, p. 1) appear to 
represent the continuum of evolutionary processes underlying the 
expression of life-history variation in populations of brook trout in 
Lake Superior (Ardren 2008, pp. 1-2). As stated above, plastic 
responses allow individuals to obtain high fitness in new environments. 
Alternatively, adaptive genetic differentiation among populations may 
provide evolutionary advantages. First, there are fitness costs to 
being highly plastic. For example, plastic genotypes need to maintain 
sensory and developmental pathways in order to induce plastic responses 
that are not required by nonplastic genotypes (Relyea 2002, pp. 272-
273). Secondly, if the plastic response to a new environment is 
insufficient and directional selection favors an extreme phenotype, 
there will be genetic evolution of the trait (adaptive radiation). 
Therefore, if a population of brook trout experiences divergent 
selection in stable environments, we would expect the ecotypes to 
evolve genetic differences and nonplastic forms because the cost of 
maintaining the phenotypic plasticity would be too high. Findings in 
the Salmon Trout River indicate phenotypic plasticity plays a major 
role in the expression of the adfluvial and fluvial ecotypes while 
information from Isle Royale indicates adaptive radiation has occurred 
separating adfluvial and lacustrine coaster ecotypes. Migratory 
plasticity could be favored in situations where adfluvial and stream-
resident brook trout co-occur because the environments they occupy are 
highly variable (Huckins et al. 2008, p. 1324; Ridgway 2008, pp. 1186-
1187). The alternating selection patterns associated with these diverse 
and variable environments create a fitness advantage for plastic 
genotypes over nonplastic genotypes. In addition, the metapopulation 
structure mediated by coaster brook trout (D'Amelio and Wilson 2008, p. 
1222; Ridgway 2008, p. 1181) favors plasticity over adaptive genetic 
differences among populations because dispersal among populations 
increases environmental heterogeneity and favors an increase in trait 
reaction norm (the pattern of visible characteristics produced by a 
given genetic makeup of an organism under different environmental 
conditions; Sultan and Spencer 2002, p. 281). Alternatively, the 
adfluvial and lacustrine ecotypes on Isle Royale are physically 
isolated and in this situation, adaptive radiation would be favored 
over the evolution of phenotypic plasticity (Price 2003, pp. 1437-
1438).
    If phenotypic plasticity is the source of differences observed 
between stream-resident and brook trout, then these ecotypes are 
expressed in a single population and represent the extremes of the 
reaction norm for migratory behavior. Scribner et al. (2008, p. 10) did 
not observe genetic differences between sympatric adfluvial brook trout 
and presumed stream-resident ecotypes in the Salmon Trout River on the 
south shore of Lake Superior. Analysis of microsatellite DNA provided 
high statistical power to detect genetic differences between ecotypes. 
In fact, the authors did observe highly significant genetic differences 
between brook trout sampled above and below the impassable waterfall in 
this system. In addition, when collections from the Salmon Trout River 
were compared with native brook trout populations sampled from 10 other 
nearby tributaries, the lowest pairwise measure of genetic distinction 
was observed between the resident and adfluvial ecotypes sampled below 
the waterfall in the Salmon Trout River. D'Amelio and Wilson (2008, p. 
1221) used similar methods to document that adfluvial brook trout in 
the Nipigon Bay were not genetically distinct from presumed resident 
brook trout sampled from tributaries to the bay. These findings in the 
Salmon Trout River and the Nipigon Bay area indicate phenotypic 
plasticity likely plays a major role in the expression of the adfluvial 
and fluvial ecotypes.
    Theriault et al. (2008, pp. 417-419) used an eco-genetic model to 
demonstrate that intensive harvest of anadromous fish reduces the 
probability of migration in brook trout over the course of 100 years. 
This study provides a basic framework for understanding how fisheries-
induced selection (mortality from fishing) influences the evolution of 
alternate life-history tactics that are expressed by phenotypic 
plasticity. For example, directional selection imposed by fishing-
induced mortality on coaster brook trout confers high fitness to the 
survivors of the fishery but not necessarily with respect to natural 
selection. There is also uncertainty regarding the rate of recovery for 
expression of the adfluvial form after fishing selection is reduced or 
eliminated because there is not automatically equal directional 
selection in the opposite direction for expression of the adfluvial 
form. In the case of the coaster, habitat degradation and competition 
from nonnative salmon may exclude brook trout from habitats that would 
allow juvenile brook trout to achieve growth rates necessary to express 
the adfluvial coaster ecotype (Huckins et al. 2008, pp. 1337-1339). 
Additionally, metapopulation structure mediated by coaster brook trout 
(D'Amelio et al. 2008, p. 1348) favors plasticity over adaptive genetic 
differences among populations (Sultan and Spencer 2002, p. 281). Loss 
of coasters in most populations in Lake Superior has reduced migration 
among populations (Sloss et al. 2008, p. 1249) resulting in a reduction 
in environmental heterogeneity favoring a decrease in the reaction norm 
of traits. These studies demonstrate that human-induced selective 
forces can alter the reaction norm for a population which can result in 
the loss of plasticity needed to express the coaster life-history 
forms.
    Brook trout experts contend that if environmental conditions are 
suitable (i.e., threats are abated), the adfluvial life form of brook 
trout populations in Lake Superior can be readily reconstituted from 
purely resident stock (USFWS 2009, p. 8); this is believed unlikely for 
other salmonids (e.g., Oncorhynchus mykiss). This assertion is 
predicated on three premises. First, adult brook trout of one ecotype 
may produce offspring of the other ecotype. For example, two resident 
fish could breed and produce offspring that exhibit both the adfluvial 
and fluvial life-history strategies. Further, stream-resident and 
adfluvial ecotypes from the same population interbreed. This means that 
within a stream, individuals that exhibit the resident and adfluvial 
forms reside within and are drawn from the same population. Second, the 
chars (genus Salvelinus), including brook trout, show greater 
phenotypic plasticity than most other salmonids. Adfluvial brook trout 
do not require substantial physiological changes (for example, 
smoltification) to successfully migrate and survive in the lake 
environment. Thus, the fitness costs to maintain the genetic code for 
plasticity are likely less relative to saltwater-dwelling salmonids. 
Hence, it is reasonable to expect a brook trout population will 
maintain the ability (genetic code) to express the full array of life 
forms over time. Third, life-history strategy for

[[Page 23381]]

brook trout is strongly controlled by environmental conditions or 
triggers. As such, the experts believe that, provided the necessary 
environmental conditions or triggers exist, life forms can be expressed 
even if temporally lost from a population.
Current Population Status of Brook Trout
    The current range of native brook trout remains generally 
unchanged, extending through much of eastern North America, from 
eastern Canada, south through the Great Lakes and northeast to Georgia 
in the U.S. However, populations throughout this range have experienced 
significant declines. The current range of native brook trout started 
diminishing over the past 200 years as a result of ecosystem disruption 
following European settlement of North America (Newman and DuBois 
1997). Habitat destruction by forestry, agricultural practices, 
industrial water use, dams, and pollution were responsible for this 
decline (Power 1980, p. 141). Brook trout were once present in nearly 
every coldwater stream and river in the eastern U.S. and Canada, but 
populations began to disappear as early agriculture, timber, and 
textile practices and industries cleared the region's protective 
forests and degraded the streams with sediment and pollution (Power 
1980, p. 141; EBJV 2006, p. 1).
    Throughout much of their natural range, remaining stream 
populations have retreated into extreme headwater, high elevation, or 
upstream reaches (EBJV 2006, p. 2). In the eastern U.S., healthy stream 
populations of brook trout (wild brook trout occupying 90-100 percent 
of their historical habitat) exist in only 5 percent of subwatersheds 
(EBJV 2006, p. 2). Anadromous stocks along the U.S. coast and in many 
Canadian rivers have been decimated by dams and estuarine pollution 
(Power 1980, p. 195). In the southern portion of its range (southern 
Appalachian Mountains), brook trout populations have declined by 75 
percent, persisting now only in isolated headwater reaches (EBJV 2006, 
p. 6).
    Various threats are persistent across the brook trout range. Most 
of them involve habitat loss and degradation, such as poor land 
management, high water temperature, sedimentation (roads), 
urbanization, degraded riparian habitat, stream fragmentation (roads), 
dam inundation/fragmentation, and forestry practices (EBJV 2006, pp. 3, 
5). Poor land management associated with agriculture (such as clearing 
streamside vegetation, over-grazing sensitive areas, ineffectively 
managing nutrients, and ditching small streams) ranks as the most 
widely distributed impact to brook trout across the eastern U.S. (EBJV 
2006, p. 2). Climate change presents a significant threat to brook 
trout, with some southern portions predicted to lose between 53-97 
percent of their brook trout habitat due to high water temperatures 
(Flebbe 2006, p. 1379). While some uncertainty remains about the exact 
temperature increase that will result from climate change, the present 
range of brook trout is predicted to shrink, particularly in the 
southern Appalachians (Hudy et al. 2005, p. 5). Nonnative species are 
now present throughout most of the range (Parsons 1973, p. 5). 
Interactions with these nonnatives are considered to be among the most 
significant biological threats to brook trout rangewide (Peck 2001, 
p.13; Hudy et al. 2005, p. 3; EBJV 2006, pp. 2-3, 5). Brown trout have 
been shown to displace or reduce stream populations of brook trout 
throughout their natural range (Nyman 1970, p. 348; Fausch and White 
1981, p. 1226; Waters 1983, p. 144). Encroachment by rainbow trout has 
also been documented in the contraction of the range of native brook 
trout across their native range (Kelly et al., 1980, pp. 9-10; Power 
1980, p. 195; Larson and Moore 1985, p. 200). Species such as small 
mouth bass and yellow perch are considered to be significant 
competitors with lake-dwelling brook trout (EBJV 2006, pp. 22, 28, 34).
Current Population Status of Brook Trout in the Upper Great Lakes
    Brook trout populations throughout the upper Great Lakes region are 
relatively common and geographically widespread, although distribution 
and abundance is much reduced from historical levels (Power 1980, p. 
195; Becker 1983, pp. 321-322; WIDNR and USFWS 2005, p. 17). Dramatic 
declines in abundance and distribution of both coaster and stream-
resident ecotypes of brook trout occurred in the upper Great Lakes from 
the 1850s to mid-1900s (Goodier 1982, pp. 110, 112; Ritchie and Black 
1988, p. 15; Newman and Dubois 1997, pp. 4-6; Enterline 2000, p. 1; 
WIDNR and USFWS 2005, pp. 17-18; Schreiner et al. 2008, p. 1305; 
Schreiner et al. 2008, p. 1351; Huckins et al. 2008, p. 1322).
    There are presently at least 200 streams with documented brook 
trout populations in the upper Great Lakes (Moore and Bream 1965, p. 
19; Goodier 1982, p. 110; Enterline 2000, p. 30; Newman et al. 2003, 
pp. 31-37; Quinlan 2004, unpub. data; Bassett 2009, unpub. data; Ward 
2007, p. 16; Schram 2008b, pers. comm.; Scott 2008, pers. comm.; Chase 
2009, pers. comm.; OMNR 2009, unpub. data). The current specific status 
of most of these populations is not known, but they are described by 
the Michigan, Minnesota, and Wisconsin natural resource agencies as 
stable and self-sustaining in the upper Great Lakes (Holtz 2008, p. 2; 
MIDNR 2008a, p. 49; Schreiner and Ebbers 2008, pers. comm.).
    In coldwater tributaries to the upper Great Lakes, brook trout were 
historically distributed from the river mouth upstream to the 
headwaters or to impassible barriers (Smith and Moyle 1944, p. 119; 
Moore and Braem 1965, p. 19; Goodier 1982, p. 111; Becker 1983, p. 321; 
WIDNR and USFWS 2005). The brook trout numbers in these stream reaches 
once numbered in the hundreds to thousands (Huckins and Baker 2008, p. 
1231). A 30-year data set from Wisconsin tributaries shows that, in 
streams historically occupied solely by brook trout, brook trout have 
contracted into upstream sections and are now nearly absent in lower 
reaches (WIDNR 2008, unpub. data). Brook trout abundance has declined 
despite the persistence of suitable conditions for brook trout and high 
numbers of juvenile nonnative salmonids (WIDNR 2008, unpub. data). In 
Wisconsin tributaries to Lake Superior, the distribution of stream-
resident brook trout populations has declined by nearly 50 percent from 
historical levels (WIDNR and USFWS 2005, p. 17).
    Historically, 119 tributaries to Lake Superior and purportedly 6 
Lake Huron streams supported populations of brook trout with coaster 
ecotypes (Newman et al. 2003, pp. 31-38; Enterline 2000, p. 30). Once 
abundant and widespread throughout the northern portions of the Great 
Lakes, populations of brook trout that still exhibit the coaster 
ecotypes are presently limited to a few locations (Dehring and Krueger 
1985, p. 1; Bailey and Smith 1981, p. 1549; Goodyear et al. 1982, pp. 
63-65; Enterline 2000, p. 30; Newman et al. 2003, p. 39; Schreiner et 
al. 2008, p. 1351; Mucha and Mackereth 2008, p. 1). Although self-
sustaining populations of stream-resident brook trout are currently 
present in 56 of 58 U.S. streams and in all 61 Canadian streams 
identified in the Brook Trout Rehabilitation Plan for Lake Superior as 
historically supporting populations with coaster ecotypes (Newman et 
al. 2003, pp. 31-37; Quinlan 2008, unpub. data; Schreiner 2008, pers. 
comm.; Schram 2008c, pers. comm.; Scott 2008, pers. comm.; Chase 2009, 
pers. comm.), only 18 populations with coaster ecotypes still persist 
there (15 stream-spawning-adfluvial, and 3 lake-spawning-lacustrine) 
(Goodyear 1982, pp. 63-65; Quinlan 1999, p. 19; Ritchie and Black

[[Page 23382]]

1988, p. 15; Swainson 2001, p. 41; Newman et al. 2003, pp. 28-39; 
Enterline 2000, p. 30; Chase 2009, pers. comm.).
    Over the last decade, the presence of coaster brook trout has been 
confirmed in other locations within the upper Great Lakes. Surveys, and 
in some cases genetic analysis, have confirmed the presence of brook 
trout with coaster ecotypes in the following locations; Minnesota 
tributaries to Lake Superior (Newman et al. 1999, p. 2; Burnham-Curtis 
2000, p. 4; Pranckus and Ostazeski 2003, p. 5; Ward 2007, p. 16), three 
Michigan tributaries to Lake Superior (Stimmel 2006, p. 56; MIDNR 
2008a, p. 2; Leonard 2009, pers. comm.), along the shoreline of the Red 
Cliff Indian Reservation, Wisconsin (Stott and Quinlan 2008, p. 21), 
and in Little Todd Harbor and Rock Harbor, Isle Royale (Gorman et al. 
2008, p. 1257). The origin of these fish is unknown and natural 
reproduction of fish exhibiting the coaster ecotype has not been 
confirmed, therefore these locations are not identified as supporting 
self-sustaining populations. However, they have potential to be self-
sustaining populations, as outlined by Schreiner et al. (2008).
    Abundance of individuals in populations exhibiting the coaster 
ecotypes is stable or increasing in several regions of Lake Superior. 
In the Salmon Trout River, Michigan, abundance as determined by video 
surveillance increased from 118 to 243 in the period from 2004 to 2006 
(MIDNR 2008a, p. 6). In the Nipigon River, angler catch per hour has 
increased from the late 1980s to the present, while harvest has 
decreased substantially (Houle 2004, p. 13). In South Bay, Lake 
Nipigon, estimates of spawner abundance continue to increase and 
currently number about 600 fish--up from fewer than 100 in the recent 
past, but still fewer than the estimated 2,500 present in the mid-1900s 
(Swainson 2009, pers. comm.). In Tobin Harbor, Isle Royale National 
Park, Michigan, estimates of adult brook trout from 1996, 2001, and 
2008 has remained around 200-250 fish (USFWS unpublished data). 
Relative abundance based on shoreline electrofishing index surveys in 
Tobin Harbor from 1997 to 2008 has fluctuated from 0.3 per hour to 16.7 
per hour (USFWS 2008, unpub. data).
    There are reintroduction stocking efforts ongoing in several 
streams on the Grand Portage Indian Reservation (Newman and Johnson 
1996, p. 4), Red Cliff Indian Reservation, Keweenaw Bay Indian 
Community Reservation (Donofrio 2002, p. 1), and in Whittlesey Creek, 
Wisconsin (USFWS and WIDNR 2003, p. 5). Supplementation stocking 
occurred in Siskiwit Bay, Isle Royale, from 1999 to 2005. Data 
collected to date indicates limited success with these efforts (Newman 
et al. 1999, p. 2; Quinlan 2008, pers. comm.; Stott and Quinlan 2008, 
p. 22). Reintroduction efforts in Michigan have recently been 
terminated in the Gratiot, Little Carp, Hurricane, and Mosquito Rivers 
and Sevenmile Creek (Scott 2007, pers. comm.; Loope 2007, pers. comm.).
    Threats to brook trout across its native range are also acting on 
brook trout within the upper Great Lakes. A primary impact is the 
presence of introduced fishes (e.g., non-native salmonids). Introduced 
salmonids have competitive and predatory impacts on brook trout, 
although the precise mechanisms may not be fully understood and the 
magnitude of impact may vary by species, population size, and 
environmental conditions. The decline or loss of the migratory coaster 
form has diminished connectivity among populations that once operated 
as metapopulations. Populations that occur in such isolated patches can 
be lost, increasing the possibility of extirpation. As a species, brook 
trout are known to be highly susceptible to exploitation by anglers 
(Newman and Dubois 1996, p. 3; Newman et al. 2003, p. 11; Huckins et 
al. 2008, p. 1322). Overharvest was a primary cause of the decline of 
Great Lakes brook trout populations by the early 1900s, especially the 
coaster ecotype, and continues to threaten some populations within the 
region (Newman and Dubois 1996, p. 1; Huckins et al. 2008, p. 1322; 
Schreiner et al. 2008, p. 1356). Climate change also presents a threat 
to upper Great Lakes brook trout, through increased water temperatures, 
leading to increased presence of nonnative competitors and predators 
along with a decrease in habitat suitability. Although the enormous 
coldwater reservoir within the lake environment represents a potential 
refuge for Great Lakes brook trout, predicted impacts in both stream 
and lake environments still represent a potential threat to their long-
term viability.

Defining a Species Under the Act

    Section 3(16) of the Act defines ``species'' to include ``any 
species or subspecies of fish and wildlife or plants, and any distinct 
vertebrate population segment of fish or wildlife that interbreeds when 
mature'' (16 U.S.C. 1532 (16)). Our implementing regulations at 50 CFR 
424.02 provide further guidance for 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 
previously discussed, coaster brook trout are classified as Salvelinus 
fontinalis, the same as other brook trout, and as such we do not 
consider the coaster form of the brook trout to constitute a distinct 
species or subspecies. Since the coaster brook trout is not a distinct 
species or subspecies, we then evaluated whether the coaster brook 
trout is a distinct vertebrate population segment to determine whether 
it would constitute a listable entity under the Act.
    To interpret and implement the distinct vertebrate population 
segment (DPS) provisions of the Act and Congressional guidance, the 
Service and the National Marine Fisheries Service (now the National 
Oceanic and Atmospheric Administration--Fisheries), published the 
Policy Regarding the Recognition of Distinct Vertebrate Population 
Segments (DPS Policy) in the Federal Register on February 7, 1996 (61 
FR 4722). Under the DPS Policy, three elements are considered in the 
decision regarding the establishment and classification of a population 
of a vertebrate species as a possible DPS. These are applied similarly 
for additions to and removals from the List of Endangered and 
Threatened Wildlife and Plants. These elements are (1) the discreteness 
of a population 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, delisting, or 
reclassification.

Distinct Vertebrate Population Segment Analysis

    In accordance with our DPS Policy, this section details our 
analysis of the first two elements used to assess whether a vertebrate 
population segment under consideration for listing may qualify as a 
DPS. These elements are (1) the population segment's discreteness from 
the remainder of the species to which it belongs and (2) the 
significance of the population segment to the species to which it 
belongs. Discreteness refers to the ability to circumscribe a 
population segment from other members of the taxon based on either (1) 
physical, physiological, ecological, or behavioral factors or (2) 
international boundaries that result in

[[Page 23383]]

significant differences in control of exploitation, habitat management, 
conservation status, or regulatory mechanisms in light of section 
4(a)(1)(B) of the Act.
    Under our DPS Policy, if we have determined that a vertebrate 
population segment is discrete, we consider its biological and 
ecological significance to the larger taxon to which it belongs 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. To evaluate 
whether a discrete vertebrate population may be significant to the 
taxon to which it belongs, we consider the best available scientific 
evidence. This evaluation may include, but is not limited to: (1) 
Evidence of the persistence of the discrete population segment in an 
ecological setting that is unusual or unique for the taxon; (2) 
evidence that loss of the population segment would result in a 
significant gap in the range of the taxon; (3) evidence that the 
population segment represents the only surviving natural occurrence of 
a taxon that may be more abundant elsewhere as an introduced population 
outside its historical range; and (4) evidence that the discrete 
population segment differs markedly in its genetic characteristics from 
other populations of the species.
    The first step in our DPS analysis was to identify population 
segments of the brook trout to evaluate. The petition asked us to (1) 
``list as `endangered' the naturally spawning anadromous (lake-run) 
Coaster Brook Trout (Salvelinus fontinalis) throughout its known 
historic range in the conterminous United States'' (including 
designation of critical habitat) and (2) ``determine whether the Salmon 
Trout River (STR) coaster is a DPS'' and (3) ``whether the south shore 
of Lake Superior population of coasters (which are known to breed today 
only in the STR) is `endangered.' '' Although brook trout in the Great 
Lakes exhibit three life-history forms (fluvial, adfluvial, and 
lacustrine), the petition specifically focused on the coaster, or 
adfluvial and lacustrine, forms.
    To address the entity identified in the first petition request 
(coaster brook trout throughout their historical range in the U.S.), we 
identified two approaches to analyzing a potential population segment: 
(1) Describe and analyze an upper Great Lakes ``all brook trout'' 
population segment, which includes all brook trout life forms--fluvial, 
adfluvial, and lacustrine ecotypes, inclusive of coaster brook trout--
present throughout the documented historical range of brook trout in 
the Great Lakes basin, and (2) describe and analyze an upper Great 
Lakes ``coaster-only'' population segment, which includes only the 
coaster forms--adfluvial and lacustrine ecotypes--of brook trout 
throughout the documented historical range of brook trout in the Great 
Lakes basin.
    We find that neither of the population segments analyzed constitute 
a valid DPS, and therefore the first petitioned entity, coaster brook 
trout throughout their historical range in the U.S., is not a valid 
DPS. To address the second and third petition requests, we focused on 
the brook trout population in the Salmon Trout River and evaluated 
whether it qualified as a DPS per our policy. We find that the brook 
trout population in the Salmon Trout River also does not constitute a 
valid DPS. The remainder of this section details the evaluation of 
these population segments as DPSs per our 1996 DPS Policy.

Upper Great Lakes All Brook Trout Population Segment

    This population segment encompasses the range of brook trout 
populations within the Great Lakes basin that currently or historically 
occupied both the tributary and lake environments (including stream-
resident, adfluvial, and lacustrine ecotypes of brook trout). Although 
technically not one of the ``Great Lakes,'' we include Lake Nipigon in 
Canada in this population because it is part of the Great Lakes 
drainage. The best available information indicates the known historical 
range of brook trout within the basin included all of Lake Superior and 
its drainage (including Lake Nipigon), and the northern portions of 
Lakes Michigan and Huron--specifically, that portion of Lake Michigan 
north of a line from the Sheboygan River, Wisconsin to Grand Traverse 
Bay, Michigan, and that portion of Lake Huron north of Thunder Bay, 
Michigan, eastward to include Manitoulin Island to the 81[deg]30' 
longitudinal demarcation and west of 81[deg]30' longitude (MacCrimmon 
and Campbell 1969, p. 1701; Dehring and Krueger 1985, p. 1; Enterline 
2000, pp. 29-30).

Discreteness

Marked Separation

    As previously described, the Upper Great Lakes brook trout 
population segment we have evaluated encompasses the range of brook 
trout populations that currently or historically occupied both the 
tributary and lake environments within the Great Lakes basin. Brook 
trout within this population segment are physically isolated from other 
populations of brook trout as the result of the physical separation 
between the drainage of the Great Lakes basin and neighboring 
drainages. Consequently, brook trout in the Great Lakes basin meet the 
discreteness criterion of being markedly separate from other members of 
the brook trout taxon.

International Border

    We presently do not find that the brook trout in the Upper Great 
lakes on either side of the international United States border with 
Canada are discrete due to differences in control of exploitation, 
management of habitat, conservation status, or regulatory mechanisms 
that are significant in light of section 4(a)(1)(D) of the Act.

Conclusion for Discreteness

    In conclusion, we determine that the Upper Great Lakes brook trout 
population segment, as defined here, is discrete from the remainder of 
the brook trout taxon. This discreteness arises from the population 
segment's physical isolation from the remainder of the taxon. 
Therefore, we will now consider the potential significance of this 
discrete population segment to the remainder of the taxon.
Significance
    We have determined that the population of brook trout in the Upper 
Great Lakes meets the discreteness elements of the DPS policy, and as 
such, we will now evaluate whether this specific population is 
significant to the taxon as a whole (i.e., native brook trout in 
eastern North America). A discrete population is considered significant 
under the DPS policy if it meets one of four of the elements identified 
in the policy under significance or can otherwise be reasonably 
justified as being significant.
    We discuss further below our evaluation of the significance of the 
population of brook trout in the Upper Great Lakes relative to the 
taxon as a whole.

Evidence of the Persistence of the Discrete Population Segment in an 
Ecological Setting That Is Unusual or Unique for the Taxon

    On the basis of an evaluation of the best available scientific 
information, we have determined that the habitat for brook trout in the 
Upper Great Lakes does not represent an ecological setting that is 
unusual or unique for the native brook trout relative to the habitat 
available to it throughout the entire

[[Page 23384]]

taxon's range in eastern North America. A summary of our evaluation is 
below.
    Brook trout exhibiting differing life-history forms occupy a 
variety of ecosystems from subarctic regions of the Hudson Bay coast, 
to temperate areas bordering and east of the Great Lakes, and southern 
coldwater habitats in the Appalachian Mountains of Tennessee and 
Georgia (Power 1980, p. 142). They have been successfully naturalized 
in western North America, South America, Eurasia, Africa, and New 
Zealand (MacCrimmon and Campbell 1969, p. 1699, pp. 1703-1717). Within 
their large native range in eastern North America, brook trout habitat 
includes coastal areas and various-sized lakes, streams, and rivers at 
varying altitudes. Most populations inhabit coldwater streams, but 
lake-dwelling and lake-spawning (lacustrine form) populations also 
occur throughout the range, in spring-fed ponds, small- to medium-sized 
lakes, and a few large, oligotrophic (containing relatively little 
plant life or nutrients, but rich in dissolved oxygen) lakes. 
Anadromous populations (``salters'') of brook trout use marine habitats 
in Hudson Bay and along the Atlantic coast.
    The upper Great Lakes represent a complex ecological setting for 
brook trout. The very large size of the Great Lakes watershed creates 
an environment that more closely resembles oceanic physical conditions 
(available to the anadromous forms of brook trout) than conditions in 
smaller lakes (available to other forms of brook trout). With 
approximately 1,500 tributaries and almost 2,800 miles (4,506 km) of 
shoreline, Lake Superior also provides brook trout access to a very 
large freshwater habitat network. Although the Great Lakes are the 
largest freshwater water bodies occupied by brook trout, there are 
thousands of lakes in its range including large postglacial lakes 
further north in Canada that contain populations of the adfluvial and 
lacustrine forms (e.g., Fraser and Bernatchez 2008, p. 1193).
    If predicted rising water temperatures in response to climate 
change are realized over the entire range of brook trout, the 
distributions of brook trout populations would probably shift toward 
cooler waters at higher latitudes and altitudes (Meisner 1990b, p. 
1068; Magnuson et al. 1997, p. 859; Kling et al. 2003, pp. 53-54). The 
greatest effects would likely begin in populations located at the 
margins of the taxon's hydrologic and geographic distributions (Meisner 
et al. 1990a, p. 282, Kling et al. 2003, p. 54). Although the upper 
Great Lakes have already experienced some impacts of climate change 
(see Kling et al. 2003, pp. 14-16) and will not be immune to future 
impacts (see Kling et al. 2003, pp. 21-25), they may provide 
substantial coldwater habitat for brook trout in the future. However, 
brook trout have abundant coldwater habitat available in the northern 
latitudes of its range, and habitat in northern North America which is 
presently too cold may develop into appropriate brook trout habitat 
under a warming scenario. We will further evaluate the extent that this 
may be the case in the range-wide assessment of native brook trout that 
we plan to conduct (see Finding section).
    Although the upper Great Lakes represent a diverse and complex 
ecological setting which may offer potential coldwater habitat for 
brook trout, we must evaluate the breadth of ecological diversity of 
brook trout habitat rangewide in our assessment of this population 
segment's significance to the rest of the taxon. First, available 
information indicates that the large area and wide geographical range 
of brook trout habitats, which vary in latitude and altitude and water 
form, contain a vast diversity of habitats for brook trout. The 
ecological setting of the upper Great Lakes is a small portion of the 
brook trout range, and based on available information, its relative 
significance to the brook trout species is limited. Second, although we 
expect that the Great Lakes may offer substantial coldwater habitat, 
there are other large, deep, oligotrophic lakes, and numerous lakes and 
streams at higher latitudes that may buffer the species from potential 
climate change impacts. Given the available information on the 
diversity and extent of ecological settings of brook trout in the rest 
of its range, we conclude at this time that the upper Great Lakes is a 
not unique or unusual setting of significance for the native brook 
trout in eastern North America.

Evidence That Loss of the Population Segment Would Result in a 
Significant Gap in the Range of the Taxon

    Loss of brook trout, including any or all life forms, in the upper 
Great Lakes, when considered in relation to brook trout throughout the 
remainder of the spe