Source: s3://data.kl3m.ai/documents/govinfo/USCOURTS/USCOURTS-caDC-07-05179/USCOURTS-caDC-07-05179-0/pdf.json

Nature of Suit Code: 893
Nature of Suit: Environmental Matters
Cause of Action: 

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United States Court of Appeals 

FOR THE DISTRICT OF COLUMBIA CIRCUIT

Argued April 4, 2008 Decided July 8, 2008 

No. 07-5179 

AMERICAN WILDLANDS, ET AL., 

APPELLANTS

v. 

DIRK KEMPTHORNE, SECRETARY, U.S. DEPARTMENT OF THE 

INTERIOR AND DALE HALL, DIRECTOR, U.S. FISH AND 

WILDLIFE SERVICE, 

APPELLEES

______ 

Appeal from the United States District Court 

for the District of Columbia 

(No. 05cv01043) 

Abigail M. Dillen argued the cause for appellants. With her 

on the briefs was Timothy J. Preso. Douglas L. Honnold entered 

an appearance. 

Lane M. McFadden, Attorney, U.S. Department of Justice, 

argued the cause for appellees. With him on the briefs were 

Andrew C. Mergen and Jennifer L. Scheller, Attorneys. 

Before: SENTELLE, Chief Judge, and GARLAND and 

GRIFFITH, Circuit Judges. 

USCA Case #07-5179 Document #1126061 Filed: 07/08/2008 Page 1 of 19
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Opinion for the court filed by Circuit Judge GRIFFITH. 

GRIFFITH,Circuit Judge: The westslope cutthroat trout has 

historically inhabited rivers and streams across parts of 

Montana, Wyoming, Idaho, Oregon, and Washington. Its 

scientific name, Oncorhynchus clarki lewisi, pays homage to 

Lewis and Clark, the storied explorers who encountered the fish 

in 1805 at the Great Falls of the Missouri River. Plaintiffs 

maintain that interbreeding with other members of the trout 

family — a phenomenon called hybridization — has so 

imperiled the continued existence of the fish that the 

government should list it as threatened under the Endangered 

Species Act. 

On appeal, plaintiffs argue that the government’s decision 

not to do so was arbitrary and capricious because the agency 

included in its count of westslope cutthroat trout hybridized fish, 

which embodied the menace at issue. Plaintiffs also appeal the 

district court’s denial of their motion to supplement the record 

with letters supporting their case. Although new data might 

require a future listing of the fish as threatened, we conclude the 

agency engaged in reasoned decisionmaking based on the best 

available science, and the district court did not abuse its 

discretion in refusing to supplement the record. 

I. 

A. 

The Endangered Species Act (“ESA”), 16 U.S.C. §§ 1531 

et seq., requires the Secretary of the Interior to determine 

whether any species is “threatened” or “endangered,” id.

§ 1533(a)(1), a responsibility he has delegated to the 

Department of the Interior’s Fish and Wildlife Service 

USCA Case #07-5179 Document #1126061 Filed: 07/08/2008 Page 2 of 19
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(“Service”), 50 C.F.R. § 402.01(b). In determining whether to 

list a species as threatened or endangered, the Service must first 

define the species so the agency can estimate its population. The 

ESA treats subspecies of fish as distinct species for listing 

purposes. 16 U.S.C. § 1532(16). 

A species is endangered when it is “in danger of extinction 

throughout all or a significant portion of its range,” id.

§ 1532(6), and threatened when it is “likely to become an 

endangered species within the foreseeable future throughout all 

or a significant portion of its range,” id. § 1532(20). The ESA 

requires the Secretary to determine whether any species is 

threatened or endangered as a result of one or more identified 

factors, including the catch-all, “other natural or manmade 

factors affecting [the species’] continued existence.” Id.

§ 1533(a). The Secretary must make this decision “solely on the 

basis of the best scientific and commercial data available to 

him.” Id. § 1533(b)(1)(A). Furthermore, the ESA recognizes the 

right of “interested person[s]” to petition the agency to add or 

remove a species from the list, id. § 1533(b)(3)(A), and sets 

forth a procedure for the agency to act on the petition and 

explain its decision, id. § 1533(b)(3)–(6). 

B. 

In 1997 a fisherman and several environmental groups 

(collectively, “American Wildlands”) petitioned the Service to 

list the westslope cutthroat trout (“WCT”) as a threatened 

species. See Am. Wildlands v. Norton, 193 F. Supp. 2d 244, 249 

(D.D.C. 2002) (recounting procedural history). According to 

plaintiffs, the chief threat to the fish comes from hybridization: 

interbreeding between WCT and other members of the trout 

family, primarily the rainbow trout. Plaintiffs contend that 

hybridization puts at risk the genetic heritage that defines WCT 

as a subspecies and that equips it to survive harsh conditions. 

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After various delays, the Service determined not to list the 

species. 65 Fed. Reg. 20,120 (Apr. 14, 2000). American 

Wildlands subsequently filed suit under the Administrative 

Procedure Act (“APA”), 5 U.S.C. § 706(2)(A), claiming this 

decision was arbitrary and capricious because the Service 

included hybridized fish in the WCT population considered for 

listing. This accounting, plaintiffs argue, not only inflated the 

number of WCT, but did so with the hybridized fish that 

represented the very threat the proposed listing was intended to 

address. 

The district court granted summary judgment for the 

plaintiffs, concluding: 

[T]he agency wholly fails to reconcile its recognition of 

hybridization as a threat to WCT’s viability with its 

inclusion of hybrid stock in the population assessed for 

listing. The administrative record clearly supports a 

finding that hybridization is a threat to the WCT 

population. . . . Therefore, when [the Service] included 

hybrid stock in the population assessed for listing, it 

needed to give some reasoned explanation. . . . Without 

a scientifically based explanation of the decision, the 

Court can not but find that the decision . . . was not 

supported by the best available science, 16 U.S.C. 

§ 1553(b)(1)(A) . . . . 

Am. Wildlands, 193 F. Supp. 2d at 255–56. The court noted that 

the Service “might have drawn a distinction between 

hybridization that is a threat to a population, and hybridization 

that is benign. However, [the Service] made no attempt to draw 

such a distinction.” Id. at 256. The court remanded the listing 

decision to the agency with instructions to reconsider and issue 

a new decision within one year. Id. at 258. 

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 Following the court’s ruling, the Service announced its 

intent to conduct a new status review and requested comments 

from interested parties. Notice of Intent To Prepare a Status 

Review for the Westslope Cutthroat Trout, 67 Fed. Reg. 56,257 

(Sept. 3, 2002). The Service received numerous submissions, 

including a comprehensive report on WCT populations prepared 

by the fish and wildlife agencies of Idaho, Montana, Oregon, 

Washington, and Wyoming, in conjunction with the U.S. Forest 

Service. BRADLEY B. SHEPARD ET AL., STATUS OF WESTSLOPE 

CUTTHROAT TROUT IN THE UNITED STATES: 2002 (2003) 

(“Multistate Assessment”), App. 943–1042. 

 In August 2003 the Service again denied threatened status 

to WCT. Reconsidered Finding for an Amended Petition to List 

the Westslope Cutthroat Trout as Threatened Throughout Its 

Range, 68 Fed. Reg. 46,989 (Aug. 7, 2003) (“Reconsidered 

Finding”). The Reconsidered Finding included a general policy 

statement, in which the Service provided the explanation 

lacking in its earlier decision for why it included some 

hybridized fish in its count of WCT, and the actual status 

review, in which the Service explained its decision not to list 

WCT. The policy statement began with the claim that the 

scientific criteria for classifying species of fish “are based 

almost entirely on morphological characters.” Id. at 46,992. 

“Morphology” is “a branch of biology that deals with the form 

and structure of animals and plants.” WEBSTER’S THIRD NEW 

INTERNATIONAL DICTIONARY 1471 (1981). WCT have a number 

of morphological characteristics that scientists use to identify 

the fish, such as a distinctive spotting pattern, coloring, and a 

typical number of vertebrae, scales, and bony projections called 

“gill rakers.” See ROBERT J. BEHNKE, NATIVE TROUT OF 

WESTERN NORTH AMERICA 77–79 (1992), App. 181–83. In 

determining what fish should count as WCT, the Service relied 

on morphology as the “principal criterion” and did not consider 

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fish that conformed morphologically to WCT to pose a threat of 

hybridization. 68 Fed. Reg. at 46,994. 

The Service recognized, however, that genetic data allows 

biologists to detect “introgression” — the “entry or introduction 

of a gene from one gene complex into another,” WEBSTER’S 

THIRD NEW INTERNATIONAL DICTIONARY 1187 (1981) — in fish 

that otherwise conform morphologically to the subspecies. 68 

Fed. Reg. at 46,992. As a result, when genetic data is available, 

scientists can now detect hybridization in some instances when 

they previously could not by relying on morphology alone. 

When using genetic data to classify fish, the Service adopted a 

rule: “[F]or populations for which molecular genetic data may 

be the only data available, populations with less than 20 percent 

introgression will be considered WCT under the [ESA], whereas 

populations with more than 20 percent introgression will 

generally be excluded from the WCT subspecies.” Id. at 46,995. 

The Service settled on the 20% threshold after reviewing the 

scientific evidence and concluding that “a natural population of 

WCT with less than 20 percent of its genes derived from 

[foreign subspecies] is, most likely, morphologically 

indistinguishable from nonintrogressed populations of WCT 

with no hybrid ancestry.” Id. at 46,994. The Service also 

concluded that low levels of introgression can occur as a result 

of the natural evolutionary process and that such fish may 

“remain very valuable to the overall conservation and survival 

of that species.” Id. at 46,992. 

 In the status review the Service analyzed the threat of 

hybridization to WCT, relying on the 2002 Multistate 

Assessment as the best available science. Id. at 46,999. The 

Multistate Assessment identified populations of WCT within the 

subspecies’ historic range and classified them according to their 

actual or suspected genetic status, Multistate Assessment at 5 

(introduction), 1 (main report), App. 953–54, and then 

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according to the conservation strategy that state agencies 

employed to manage the fish, id. at 3–4 (main report), 80 (App. 

D), App. 956–57, 1033. The report had genetic data for 

approximately 21% of habitat occupied by WCT within its 

historic range. Id. at 13 (main report), App. 966. 

Drawing on data from the Multistate Assessment, the 

Service included in the WCT population count fish that fell into 

three categories: (1) genetically tested populations with 

introgression levels below 1%; (2) nongenetically tested 

populations that morphologically conformed to WCT and that 

scientists concluded likely had introgression levels below 1% 

because no records indicated that hybridizing fish, such as 

rainbow trout, were at one time stocked in the area or were 

otherwise present; and (3) populations that the Multistate 

Assessment classified as “conservation populations.” 68 Fed. 

Reg. at 46,999. This last category included fish that 

morphologically conformed to WCT and generally had less than 

10% introgression. Multistate Assessment at 3–4 (main report), 

80 (App. D), App. 956–57, 1033; see also UTAH DIVISION 

WILDLIFE RESOURCES, GENETIC CONSIDERATIONS ASSOCIATED 

WITH CUTTHROAT TROUT MANAGEMENT 4 (2000)

(“[Conservation] populations retain all the phenotypic attributes 

associated with the subspecies, though they exist in a slightly 

introgressed condition.”), App. 486. Conservation populations 

included some fish with slightly higher levels of introgression 

where the populations demonstrated a special attribute that 

biologists sought to preserve, such as an evolutionary adaptation 

to an extreme environmental condition. Multistate Assessment 

at 3–4 (main report), App. 956–57. 

 Looking to the Multistate Assessment, and considering the 

prospects for future genetic dilution, the Service acknowledged 

that hybridization “remains the greatest threat to WCT,” 68 Fed. 

Reg. at 47,006, but decided the severity of the threat did not yet 

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require listing. Importantly, the agency identified significant 

populations of nonintrogressed WCT. See id. at 47,004. 

The information that we have summarized in this 

document, particularly that obtained from the status 

update report (Shepard et al. 2003), indicates even 

greater abundance of WCT across the subspecies’ range 

than we had estimated during the initial status review 

(U.S. Fish and Wildlife Service 1999). Today, 563 

extant WCT “conservation” populations collectively 

occupy 39,349 km (24,450 mi) of stream in Idaho, 

Montana, Oregon, Washington, and Wyoming. . . . In 

our initial status review . . . we reported that WCT 

occupied about 37,015 km (23,000 mi) of stream in the 

United States. In addition, nonintrogressed WCT are 

now known to inhabit 5,633 km (3,500 mi) of stream 

and probably inhabit as many as 20,278 km (12,600 mi) 

of stream in which no potentially hybridizing fishes 

occur. In our initial status review . . . we reported that 

nonintrogressed WCT were known to occupy 4,237 km 

(2,633 mi) of stream. 

Id. at 47,006. 

The Service noted that some of these populations exist 

within reach of potentially hybridizing fish, such as the rainbow 

trout, yet have remained free from interbreeding. Id. The 

Multistate Assessment predicted that hybridization would 

continue to move upstream into areas presently occupied by 

nonintrogressed WCT, although environmental factors such as 

altitude, stream size, and water temperature may limit that 

progression. Id. at 47,004–05. Moreover, in the case of 1525 

stream miles containing pure WCT, artificial barriers would 

prevent hybridization altogether. Id. at 47,005. The Service also 

noted that to the degree hybridization persists, some “limited 

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presence” of foreign genes does not preclude classification as 

WCT — a point the agency made earlier in the policy section of 

its Reconsidered Finding. Id. at 47,006. 

 Dissatisfied with the Reconsidered Finding, plaintiffs filed 

another suit in district court under the APA, 5 U.S.C. 

§ 706(2)(A), again claiming the agency’s decision was arbitrary 

and capricious because it still counted hybridized fish in the 

WCT population. This time the court granted summary 

judgment for the agency because it found that record evidence 

supported the agency’s decision. Am. Wildlands v. Kempthorne, 

478 F. Supp. 2d 92, 99 (D.D.C. 2007). 

American Wildlands filed a timely notice of appeal on May 

25, 2007. In addition to challenging the decision not to list, 

plaintiffs also appeal the district court’s order denying their 

motion for leave to supplement the administrative record. Am. 

Wildlands v. Norton, No. 05-1043, 2006 WL 2780702 (D.D.C. 

Sept. 21, 2006). The district court had jurisdiction under the 

ESA’s citizen suit provision, 16 U.S.C. § 1540(g), and we have 

jurisdiction to hear the appeal under 28 U.S.C. § 1291. 

II. 

 The Service’s listing determination is subject to review 

under the APA and must be set aside if “arbitrary, capricious, an 

abuse of discretion, or otherwise not in accordance with law.” 5 

U.S.C. § 706(2)(A); see City of Las Vegas v. Lujan, 891 F.2d 

927, 932 (D.C. Cir. 1989). “This standard of review is a highly 

deferential one. It presumes agency action to be valid.” Ethyl 

Corp. v. EPA, 541 F.2d 1, 34 (D.C. Cir. 1976). The Supreme 

Court has explained that an agency acts arbitrarily or 

capriciously if it “has relied on factors which Congress has not 

intended it to consider, entirely failed to consider an important 

aspect of the problem, offered an explanation for its decision 

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that runs counter to the evidence before the agency, or is so 

implausible that it could not be ascribed to a difference in view 

or the product of agency expertise.” Motor Vehicle Mfrs. Ass’n 

v. State Farm Mut. Auto. Ins. Co., 463 U.S. 29, 43 (1983). 

Because the district court ruled on summary judgment, our 

review is de novo. See Castlewood Prods., L.L.C. v. Norton, 365 

F.3d 1076, 1082 (D.C. Cir. 2004). 

American Wildlands presents several arguments, each of 

which concludes that the Service’s decision not to list WCT was 

arbitrary and capricious. We disagree. 

A. 

 American Wildlands’ primary challenge is to the Service’s 

reliance on morphological data, which they argue was arbitrary 

and capricious because the agency wrongly assumed that fish 

morphologically conforming to WCT will be only slightly 

hybridized. They contend that evidence in the record shows that 

fish can have introgression levels up to 50% and still 

morphologically conform to the subspecies. See, e.g., F.W. 

Allendorf et al., Intercrosses and the U.S. Endangered Species 

Act: Should Hybridized Populations be Included as Westslope 

Cutthroat Trout? 7 (2003) (unpublished manuscript), App. 925. 

“In practice, this means that every last surviving population of 

[WCT] could be up to 50 percent hybridized before [the 

Service] would recognize hybridization as a major concern in 

the ESA listing context.” American Wildlands’ Opening Br. at 

40. This argument, plaintiffs maintain, belies the government’s 

assurance that “individual fish conforming morphologically to 

the scientific taxonomic description of WCT” will carry foreign 

genes at a “low frequency.” 68 Fed. Reg. at 46,994. Plaintiffs 

argue that even if the Service reasonably included fish having 

less than a 20% introgression level in the WCT population when 

genetic data was available, the agency arbitrarily assumed that 

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populations for which genetic data was not available would also 

have introgression levels below 20% if they morphologically 

conformed to WCT. 

 The Service concedes that its method may count some fish 

in the WCT population that morphologically conform to WCT 

but have introgression levels higher than 20%. See Service’s Br. 

at 37 (“One of the primary authors of the Service’s Finding has 

acknowledged this possibility, and the Service is well aware of 

it.”); Oral Arg. Recording at 22:10–22:36. Nonetheless, the 

agency argues that its method is reasonable. We agree and hold 

that in the absence of genetic data the Service reasonably 

included fish morphologically conforming to WCT in the 

population considered for listing. Under the ESA, listing 

determinations are to be made “solely on the basis of the best 

scientific and commercial data available.” 16 U.S.C. 

§ 1533(b)(1)(A). In Southwest Center for Biological Diversity v. 

Babbitt, we held that “[t]he ‘best available data’ requirement 

makes it clear that the Secretary has no obligation to conduct 

independent studies.” 215 F.3d 58, 60 (D.C. Cir. 2000). Rather, 

that provision “ ‘merely prohibits the Secretary from 

disregarding available scientific evidence that is in some way 

better than the evidence he relies on.’ ” Id. (quoting City of Las 

Vegas, 891 F.2d at 933) (emphasis added). 

 The “best available data” requirement in § 1533(b)(1)(A) 

requires not only that data be attainable, but that researchers in 

fact have conducted the tests. Genetic testing is a relatively new 

technique for classifying fish and though it can provide 

precision in determining introgression levels not possible on the 

basis of morphology alone, genetic data is not available for the 

large majority of WCT populations. Lacking genetic data, the 

Service did not unreasonably rely on morphological data to 

classify fish — even though, by the agency’s admission, some 

fish counted as WCT may have introgression levels greater than 

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20%. Aside from morphological assessments and absent genetic 

data, the Service had nothing else upon which to rely. 

At oral argument, American Wildlands asserted that the 

Service should “look at the genetically pure populations, . . . 

look at the threat facing those [populations], and . . . decide 

whether those populations . . . would be able to sustain the 

species in the future.” Oral Arg. Recording at 13:20–13:30. To 

agree with the plaintiffs would be to require the Service to make 

its decision only on the basis of genetic data. This rule would 

demand the absurd result that the Service must deem threatened 

any species for which it lacks genetic data. Absent a statutory 

mandate requiring the Service to collect genetic data, however, 

the Service’s method was reasonable. If plaintiffs believe the 

Service’s decision not to list WCT depended on counting fish 

which, if genetically tested, would have introgression levels 

greater than 20%, the path for plaintiffs to press their argument 

is clear: provide sufficient genetic data to substantiate this 

claim. 

 American Wildlands also argues that even if the Service 

reasonably relied on morphological data in some instances, the 

agency violated the law by relying on such data when genetic 

information was in fact available. That the plaintiffs make this 

argument in their opening brief is understandable. In its 

Reconsidered Finding, the Service stated that morphology 

would serve as the “principal criterion” for classifying fish as 

WCT and then stated, “[F]or populations for which molecular 

genetic data may be the only data available, populations with 

less than 20% introgression will be considered WCT under the 

Act.” 68 Fed. Reg. at 46,995 (emphasis added). The plaintiffs 

were not unreasonable in interpreting this statement to mean the 

Service would only use genetic data when morphological data 

was not available. 

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 In its brief, however, the Service made clear that in 

conducting its status review it always used genetic data when 

available and never included fish in the WCT population count 

that carried introgression levels greater than 20%. See Service’s 

Br. at 39 (“[M]olecular genetic data was used whenever 

available, and populations of fish with higher than 20% genetic 

introgression were rejected for classification as westslope 

cutthroat trout.”); id. at 39 n.10 (explaining that in conducting 

the status review the Service never encountered a population for 

which it had both morphological data and genetic data showing 

fish with introgression levels greater than 20%). At oral 

argument, the government was even more firm: 

[COURT]: “So we’ve settled that if you have genetic 

data as well as morphology, you will not ignore the 

genetic data.” 

[SERVICE]: “Correct.” 

Oral Arg. Recording at 21:52–22:01. Although our decision 

might be different if the Service had refused to rely on available 

genetic data, that did not happen here. 

B. 

 

Plaintiffs also challenge the agency’s decision to include 

fish in the WCT population count having introgression levels as 

high as 20%. When pressed at oral argument, American 

Wildlands would not identify a threshold introgression level. 

See Oral Arg. Recording at 16:13–17:17, 38:50–42:50. And in 

their briefs, plaintiffs argue that the best available science does 

not deem any level of introgression benign. 

To support this claim, plaintiffs point to a scientific paper in 

the record suggesting that introgression always risks the loss of 

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genetic diversity, which in turn can reduce resistance to disease 

and diminish an organism’s ability to adapt to changing 

environmental conditions. See F.W. Allendorf & R.F. Leary, 

Conservation and Distribution of Genetic Variation in a 

Polytypic Species, the Cutthroat Trout, CONSERVATION 

BIOLOGY 170, 180 (1988), App. 89. In addition, plaintiffs point 

to a paper which they argue establishes that fish bearing low 

levels of introgression and morphologically conforming to WCT 

may nonetheless display behavioral differences. See N. Hitt, 

Hybridization Between Westslope Cutthroat Trout and Rainbow 

Trout: Distribution and Limiting Factors (2002) (unpublished 

master’s thesis), App. 626–713. In particular, they contend, Hitt 

shows that “slightly hybridized fish are dispersing and 

colonizing new territory at rates that are atypical of [WCT] in 

Montana’s Flathead River System. Notably, these are fish that 

are hybridized at low levels that [the Service] deemed to be 

benign.” American Wildlands’ Opening Br. at 43 (citation 

omitted). This tendency is referred to as “straying.” 

Because we have held that the Service was reasonable to 

count as WCT fish that morphologically conformed to the 

subspecies when the agency lacked genetic data, we consider 

this challenge only in those instances where the Service had 

genetic data. We conclude the agency did not act arbitrarily or 

capriciously by including fish with introgression levels below 

20%. 

As an initial matter, record evidence supports the 

conclusion that fish having less than 20% foreign genes are 

morphologically indistinguishable from nonintrogressed 

populations. See, e.g., 68 Fed. Reg. at 46,993–94 (citing 

sources). Moreover, scientific papers in the record suggest that 

low levels of introgression may, in fact, make a positive 

contribution to the long-term survival of a subspecies. For 

example, a peer review of another article by Allendorf, which 

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article made the same claim about the harmful effects of any 

hybridization, warned that some of the paper’s statements on 

this issue amounted to “speculation” and suggested that low 

levels of genetic introgression could allow WCT to better adapt 

to extreme environmental conditions, such as fires, floods, or 

droughts. D. Campton, Peer Review of Draft Report by F.W. 

Allendorf and L.L. Lundquist, Hybridization, Fitness, and 

Conservation of Westslope Cutthroat Trout (2002), App. 861. 

Likewise, the Hitt paper did not draw a conclusion based on 

evidence, but only suggested further research. Hitt, 

Hybridization Between Westslope Cutthroat Trout and Rainbow 

Trout 53 (“[T]he effects of [rainbow trout] introgression on 

straying rates should be assessed. . . . [Rainbow trout] 

introgression could introduce a genetic predisposition to 

stray. . . . To test this hypothesis, one would first have to 

determine . . . . ”) (emphasis added), App. 686. 

Under these circumstances, we defer to the agency’s 

decisionmaking. “The rationale for deference is particularly 

strong when the [agency] is evaluating scientific data within its 

technical expertise: ‘[I]n an area characterized by scientific and 

technological uncertainty[,] . . . this court must proceed with 

particular caution, avoiding all temptation to direct the agency 

in a choice between rational alternatives.’ ” Int’l Fabricare Inst. 

v. EPA, 972 F.2d 384, 389 (D.C. Cir. 1992) (quoting Envtl. Def. 

Fund v. Costle, 578 F.2d 337, 339 (D.C. Cir. 1978)); see also 

Balt. Gas & Elec. Co. v. Natural Res. Def. Council, 462 U.S. 87, 

103 (1983) (noting that a reviewing court must be “at its most 

deferential” when examining conclusions made “at the frontiers 

of science”). And again we note that in the absence of available 

evidence, Congress does not require the agency to conduct its 

own studies. See 16 U.S.C. § 1533(b)(1)(A); Sw. Ctr. for 

Biological Diversity v. Babbitt, 215 F.3d 58, 60 (D.C. Cir. 

2000). Where the agency used genetic data, we defer to the 

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Service’s decision to include fish in the listing population 

having introgression levels below 20%.

C. 

 American Wildlands further argues that the Service’s policy 

of including some introgressed fish in the WCT count is an 

arbitrary departure from past practice. In at least one previous 

listing determination, plaintiffs aver, the Service only counted 

fish as members of the subspecies considered for listing when 

they had introgression levels below 1%. American Wildlands’ 

Reply Br. at 22 (citing Candidate Status Review for Rio Grande 

Cutthroat Trout, 67 Fed. Reg. 39,936 (June 11, 2002)). 

 We need not consider this argument because plaintiffs have 

forfeited it on appeal, having raised it for the first time in their 

reply brief. See Rollins Envtl. Servs. v. EPA, 937 F.2d 649, 652 

n.2 (D.C. Cir. 1991) (“Issues may not be raised for the first time 

in a reply brief.”). In the statement of facts section of its opening 

brief, American Wildlands did explain that in a past assessment 

the Service only counted fish as Rio Grande Cutthroat Trout 

having less than 1% introgression. American Wildlands’ 

Opening Br. at 23–25. But explaining the factual basis in the 

opening brief for an argument not made until the reply brief is 

insufficient to raise the claim. See Karst Envtl. Educ. & Prot., 

Inc. v. EPA, 475 F.3d 1291, 1299 (D.C. Cir. 2007); PDK Labs., 

Inc. v. U.S. Drug Enforcement Admin., 438 F.3d 1184, 1196 

(D.C. Cir. 2006). 

 The only place where plaintiffs mention the argument in 

their opening brief is at the very end of the section addressing 

the agency’s decision in the Reconsidered Finding, where they 

state: 

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[T]he [ESA] does not permit [the Service] to continue 

using inaccurate data simply because it is more 

convenient to do so — particularly when the agency has 

at its disposal the principled genetic criteria developed 

for the Rio Grande cutthroat trout listing. See id.; see 

also, e.g., Friends of the Wild Swan, 12 F. Supp. 2d at 

1135 (finding the [Service] violated the [ESA] in 

ignoring the most reliable data and further stressing that 

“[a]n agency acts arbitrarily when it departs from its 

precedent without giving good reason”) (citing 

Northern California Power Agency v. F.E.R.C., 37 F.3d 

1517, 1522 (9th Cir. 1994)). 

American Wildlands’ Opening Br. at 48 (emphasis added; all 

brackets added except final set). A fleeting statement in the 

parenthetical of a citation is no more sufficient to raise a claim 

than a cursory remark in a footnote, which we have consistently 

rejected. See, e.g., Hutchins v. District of Columbia, 188 F.3d 

531, 539 n.3 (D.C. Cir. 1999) (“We need not consider cursory 

arguments made only in a footnote . . . . ”); see also Wash. Legal 

Clinic for the Homeless v. Barry, 107 F.3d 32, 39 (D.C. Cir. 

1997) (“Because the District raises this issue in such a cursory 

fashion, we decline to resolve it.”) (internal quotation marks 

omitted); Ry. Labor Executives’ Ass’n v. U.S. R.R. Ret. Bd., 749 

F.2d 856, 859 n.6 (D.C. Cir. 1984) (declining to resolve an issue 

that “consisted of only three sentences in the [appellant’s] brief 

and no discussion of the . . . relevant case law”). 

III. 

 Lastly, American Wildlands appeals the district court’s 

denial of its motion to supplement the record with two letters 

from scientists whose work the Service considered in deciding 

not to list WCT. We review the district court’s refusal to 

supplement the administrative record for abuse of discretion. 

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18 

Novartis Pharm. Corp. v. Leavitt, 435 F.3d 344, 348 (D.C. Cir. 

2006). 

 When reviewing agency action under the APA, we review 

“the whole record or those parts of it cited by a party.” 5 U.S.C. 

§ 706. The record consists of the order involved, any findings or 

reports on which that order is based, and “the pleadings, 

evidence, and other parts of the proceedings before the agency.” 

FED. R. APP. P. 16(a). Ordinarily, “review is to be based on the 

full administrative record that was before the Secretary at the 

time he made his decision.” Citizens to Preserve Overton Park, 

Inc. v. Volpe, 401 U.S. 402, 420 (1971); see also Walter O. 

Boswell Mem’l Hosp. v. Heckler, 749 F.2d 788, 792 (D.C. Cir. 

1984). We do not allow parties to supplement the record “unless 

they can demonstrate unusual circumstances justifying a 

departure from this general rule.” Tex. Rural Legal Aid, Inc. v. 

Legal Servs. Corp., 940 F.2d 685, 698 (D.C. Cir. 1991). We 

have recognized such circumstances in at least three instances, 

see James Madison Ltd. by Hecht v. Ludwig, 82 F.3d 1085, 

1095 (D.C. Cir. 1996) (collecting cases): (1) “[T]he agency 

deliberately or negligently excluded documents that may have 

been adverse to its decision,” id.; (2) “the district court needed 

to supplement the record with ‘background information’ in 

order to determine whether the agency considered all of the 

relevant factors,” id.; or (3) “the agency failed to explain 

administrative action so as to frustrate judicial review,” id.

(internal quotation marks and brackets omitted). 

 We hold the district court did not abuse its discretion in 

denying the motion to supplement the record. Both letters were 

written after the Service issued its Reconsidered Finding, and 

are therefore not part of the administrative record. Moreover, 

they do not satisfy any of the “unusual circumstances” 

previously listed. Rather, as the district court correctly 

concluded, Am. Wildlands v. Norton, No. 05-1043, 2006 WL 

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19 

2780702, at *2–4 (D.D.C. Sept. 21, 2006), they merely disagree 

with the Service’s conclusions, see, e.g., Letter from N.P. Hitt, 

Professor, Dept. of Fisheries & Wildlife Scis., Va. Polytechnic 

Inst. & State Univ., to L.R. Keading, Chief, Branch of Native 

Fishes Mgmt. (July 10, 2004), reprinted at App. 1120 (“[W]e 

disagree with the [Service’s] interpretation of our data on 

several counts and believe that the current introgression policy 

does not represent the best available scientific information.”). 

 

IV. 

Because American Wildlands has not shown that the 

Service’s decision to deny listing the westslope cutthroat trout 

as a threatened species was arbitrary or capricious, and because 

plaintiffs have not shown that the district court abused its 

discretion in denying the motion to supplement the record, we 

affirm the district court in all respects. 

So ordered. 

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